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Message-ID: <20161025094632.g266t632x5fplqua@thigreal>
Date: Tue, 25 Oct 2016 12:46:32 +0300
From: Hans Liljestrand <ishkamiel@...il.com>
To: AKASHI Takahiro <takahiro.akashi@...aro.org>
Cc: kernel-hardening@...ts.openwall.com, keescook@...omium.org,
Elena Reshetova <elena.reshetova@...el.com>,
David Windsor <dwindsor@...il.com>
Subject: Re: [RFC v2 PATCH 01/13] Add architecture
independent hardened atomic base
On Tue, Oct 25, 2016 at 05:51:11PM +0900, AKASHI Takahiro wrote:
> On Thu, Oct 20, 2016 at 01:25:19PM +0300, Elena Reshetova wrote:
> > This series brings the PaX/Grsecurity PAX_REFCOUNT [1]
> > feature support to the upstream kernel. All credit for the
> > feature goes to the feature authors.
> >
> > The name of the upstream feature is HARDENED_ATOMIC
> > and it is configured using CONFIG_HARDENED_ATOMIC and
> > HAVE_ARCH_HARDENED_ATOMIC.
> >
> > This series only adds x86 support; other architectures are expected
> > to add similar support gradually.
> >
> > Feature Summary
> > ---------------
> > The primary goal of KSPP is to provide protection against classes
> > of vulnerabilities. One such class of vulnerabilities, known as
> > use-after-free bugs, frequently results when reference counters
> > guarding shared kernel objects are overflowed. The existence of
> > a kernel path in which a reference counter is incremented more
> > than it is decremented can lead to wrapping. This buggy path can be
> > executed until INT_MAX/LONG_MAX is reached, at which point further
> > increments will cause the counter to wrap to 0. At this point, the
> > kernel will erroneously mark the object as not in use, resulting in
> > a multitude of undesirable cases: releasing the object to other users,
> > freeing the object while it still has legitimate users, or other
> > undefined conditions. The above scenario is known as a use-after-free
> > bug.
> >
> > HARDENED_ATOMIC provides mandatory protection against kernel
> > reference counter overflows. In Linux, reference counters
> > are implemented using the atomic_t and atomic_long_t types.
> > HARDENED_ATOMIC modifies the functions dealing with these types
> > such that when INT_MAX/LONG_MAX is reached, the atomic variables
> > remain saturated at these maximum values, rather than wrapping.
> >
> > There are several non-reference counter users of atomic_t and
> > atomic_long_t (the fact that these types are being so widely
> > misused is not addressed by this series). These users, typically
> > statistical counters, are not concerned with whether the values of
> > these types wrap, and therefore can dispense with the added performance
> > penalty incurred from protecting against overflows. New types have
> > been introduced for these users: atomic_wrap_t and atomic_long_wrap_t.
> > Functions for manipulating these types have been added as well.
> >
> > Note that the protection provided by HARDENED_ATOMIC is not "opt-in":
> > since atomic_t is so widely misused, it must be protected as-is.
> > HARDENED_ATOMIC protects all users of atomic_t and atomic_long_t
> > against overflow. New users wishing to use atomic types, but not
> > needing protection against overflows, should use the new types
> > introduced by this series: atomic_wrap_t and atomic_long_wrap_t.
> >
> > Bugs Prevented
> > --------------
> > HARDENED_ATOMIC would directly mitigate these Linux kernel bugs:
> >
> > CVE-2016-3135 - Netfilter xt_alloc_table_info integer overflow
> > CVE-2016-0728 - Keyring refcount overflow
> > CVE-2014-2851 - Group_info refcount overflow
> > CVE-2010-2959 - CAN integer overflow vulnerability,
> > related post: https://jon.oberheide.org/blog/2010/09/10/linux-kernel-can-slub-overflow/
> >
> > And a relatively fresh exploit example:
> > https://www.exploit-db.com/exploits/39773/
> >
> > [1] https://forums.grsecurity.net/viewtopic.php?f=7&t=4173
> >
> > Signed-off-by: Elena Reshetova <elena.reshetova@...el.com>
> > Signed-off-by: Hans Liljestrand <ishkamiel@...il.com>
> > Signed-off-by: David Windsor <dwindsor@...il.com>
> > ---
> > Documentation/security/hardened-atomic.txt | 141 +++++++++++++++
> > include/asm-generic/atomic-long.h | 264 ++++++++++++++++++++++++-----
> > include/asm-generic/atomic.h | 56 ++++++
> > include/asm-generic/atomic64.h | 13 ++
> > include/asm-generic/bug.h | 7 +
> > include/asm-generic/local.h | 15 ++
> > include/linux/atomic.h | 114 +++++++++++++
> > include/linux/types.h | 17 ++
> > kernel/panic.c | 11 ++
> > security/Kconfig | 19 +++
> > 10 files changed, 611 insertions(+), 46 deletions(-)
> > create mode 100644 Documentation/security/hardened-atomic.txt
> >
> > diff --git a/Documentation/security/hardened-atomic.txt b/Documentation/security/hardened-atomic.txt
> > new file mode 100644
> > index 0000000..c17131e
> > --- /dev/null
> > +++ b/Documentation/security/hardened-atomic.txt
> > @@ -0,0 +1,141 @@
> > +=====================
> > +KSPP: HARDENED_ATOMIC
> > +=====================
> > +
> > +Risks/Vulnerabilities Addressed
> > +===============================
> > +
> > +The Linux Kernel Self Protection Project (KSPP) was created with a mandate
> > +to eliminate classes of kernel bugs. The class of vulnerabilities addressed
> > +by HARDENED_ATOMIC is known as use-after-free vulnerabilities.
> > +
> > +HARDENED_ATOMIC is based off of work done by the PaX Team [1]. The feature
> > +on which HARDENED_ATOMIC is based is called PAX_REFCOUNT in the original
> > +PaX patch.
> > +
> > +Use-after-free Vulnerabilities
> > +------------------------------
> > +Use-after-free vulnerabilities are aptly named: they are classes of bugs in
> > +which an attacker is able to gain control of a piece of memory after it has
> > +already been freed and use this memory for nefarious purposes: introducing
> > +malicious code into the address space of an existing process, redirecting
> > +the flow of execution, etc.
> > +
> > +While use-after-free vulnerabilities can arise in a variety of situations,
> > +the use case addressed by HARDENED_ATOMIC is that of referenced counted
> > +objects. The kernel can only safely free these objects when all existing
> > +users of these objects are finished using them. This necessitates the
> > +introduction of some sort of accounting system to keep track of current
> > +users of kernel objects. Reference counters and get()/put() APIs are the
> > +means typically chosen to do this: calls to get() increment the reference
> > +counter, put() decrments it. When the value of the reference counter
> > +becomes some sentinel (typically 0), the kernel can safely free the counted
> > +object.
> > +
> > +Problems arise when the reference counter gets overflowed. If the reference
> > +counter is represented with a signed integer type, overflowing the reference
> > +counter causes it to go from INT_MAX to INT_MIN, then approach 0. Depending
> > +on the logic, the transition to INT_MIN may be enough to trigger the bug,
> > +but when the reference counter becomes 0, the kernel will free the
> > +underlying object guarded by the reference counter while it still has valid
> > +users.
> > +
> > +
> > +HARDENED_ATOMIC Design
> > +======================
> > +
> > +HARDENED_ATOMIC provides its protections by modifying the data type used in
> > +the Linux kernel to implement reference counters: atomic_t. atomic_t is a
> > +type that contains an integer type, used for counting. HARDENED_ATOMIC
> > +modifies atomic_t and its associated API so that the integer type contained
> > +inside of atomic_t cannot be overflowed.
> > +
> > +A key point to remember about HARDENED_ATOMIC is that, once enabled, it
> > +protects all users of atomic_t without any additional code changes. The
> > +protection provided by HARDENED_ATOMIC is not “opt-in”: since atomic_t is so
> > +widely misused, it must be protected as-is. HARDENED_ATOMIC protects all
> > +users of atomic_t and atomic_long_t against overflow. New users wishing to
> > +use atomic types, but not needing protection against overflows, should use
> > +the new types introduced by this series: atomic_wrap_t and
> > +atomic_long_wrap_t.
> > +
> > +Detect/Mitigate
> > +---------------
> > +The mechanism of HARDENED_ATOMIC can be viewed as a bipartite process:
> > +detection of an overflow and mitigating the effects of the overflow, either
> > +by not performing or performing, then reversing, the operation that caused
> > +the overflow.
> > +
> > +Overflow detection is architecture-specific. Details of the approach used to
> > +detect overflows on each architecture can be found in the PAX_REFCOUNT
> > +documentation. [1]
> > +
> > +Once an overflow has been detected, HARDENED_ATOMIC mitigates the overflow
> > +by either reverting the operation or simply not writing the result of the
> > +operation to memory.
> > +
> > +
> > +HARDENED_ATOMIC Implementation
> > +==============================
> > +
> > +As mentioned above, HARDENED_ATOMIC modifies the atomic_t API to provide its
> > +protections. Following is a description of the functions that have been
> > +modified.
> > +
> > +First, the type atomic_wrap_t needs to be defined for those kernel users who
> > +want an atomic type that may be allowed to overflow/wrap (e.g. statistical
> > +counters). Otherwise, the built-in protections (and associated costs) for
> > +atomic_t would erroneously apply to these non-reference counter users of
> > +atomic_t:
> > +
> > + * include/linux/types.h: define atomic_wrap_t and atomic64_wrap_t
> > +
> > +Next, we define the mechanism for reporting an overflow of a protected
> > +atomic type:
> > +
> > + * kernel/panic.c: void hardened_atomic_overflow(struct pt_regs)
> > +
> > +The following functions are an extension of the atomic_t API, supporting
> > +this new “wrappable” type:
> > +
> > + * static inline int atomic_read_wrap()
> > + * static inline void atomic_set_wrap()
> > + * static inline void atomic_inc_wrap()
> > + * static inline void atomic_dec_wrap()
> > + * static inline void atomic_add_wrap()
> > + * static inline long atomic_inc_return_wrap()
> > +
> > +Departures from Original PaX Implementation
> > +-------------------------------------------
> > +While HARDENED_ATOMIC is based largely upon the work done by PaX in their
> > +original PAX_REFCOUNT patchset, HARDENED_ATOMIC does in fact have a few
> > +minor differences. We will be posting them here as final decisions are made
> > +regarding how certain core protections are implemented.
> > +
> > +x86 Race Condition
> > +------------------
> > +In the original implementation of PAX_REFCOUNT, a known race condition
> > +exists when performing atomic add operations. The crux of the problem lies
> > +in the fact that, on x86, there is no way to know a priori whether a
> > +prospective atomic operation will result in an overflow. To detect an
> > +overflow, PAX_REFCOUNT had to perform an operation then check if the
> > +operation caused an overflow.
> > +
> > +Therefore, there exists a set of conditions in which, given the correct
> > +timing of threads, an overflowed counter could be visible to a processor.
> > +If multiple threads execute in such a way so that one thread overflows the
> > +counter with an addition operation, while a second thread executes another
> > +addition operation on the same counter before the first thread is able to
> > +revert the previously executed addition operation (by executing a
> > +subtraction operation of the same (or greater) magnitude), the counter will
> > +have been incremented to a value greater than INT_MAX. At this point, the
> > +protection provided by PAX_REFCOUNT has been bypassed, as further increments
> > +to the counter will not be detected by the processor’s overflow detection
> > +mechanism.
> > +
> > +The likelihood of an attacker being able to exploit this race was
> > +sufficiently insignificant such that fixing the race would be
> > +counterproductive.
> > +
> > +[1] https://pax.grsecurity.net
> > +[2] https://forums.grsecurity.net/viewtopic.php?f=7&t=4173
> > diff --git a/include/asm-generic/atomic-long.h b/include/asm-generic/atomic-long.h
> > index 288cc9e..425f34b 100644
> > --- a/include/asm-generic/atomic-long.h
> > +++ b/include/asm-generic/atomic-long.h
> > @@ -22,6 +22,12 @@
> >
> > typedef atomic64_t atomic_long_t;
> >
> > +#ifdef CONFIG_HARDENED_ATOMIC
> > +typedef atomic64_wrap_t atomic_long_wrap_t;
> > +#else
> > +typedef atomic64_t atomic_long_wrap_t;
> > +#endif
> > +
> > #define ATOMIC_LONG_INIT(i) ATOMIC64_INIT(i)
> > #define ATOMIC_LONG_PFX(x) atomic64 ## x
> >
> > @@ -29,51 +35,77 @@ typedef atomic64_t atomic_long_t;
> >
> > typedef atomic_t atomic_long_t;
> >
> > +#ifdef CONFIG_HARDENED_ATOMIC
> > +typedef atomic_wrap_t atomic_long_wrap_t;
> > +#else
> > +typedef atomic_t atomic_long_wrap_t;
> > +#endif
> > +
> > #define ATOMIC_LONG_INIT(i) ATOMIC_INIT(i)
> > #define ATOMIC_LONG_PFX(x) atomic ## x
> >
> > #endif
> >
> > -#define ATOMIC_LONG_READ_OP(mo) \
> > -static inline long atomic_long_read##mo(const atomic_long_t *l) \
> > +#define ATOMIC_LONG_READ_OP(mo, suffix) \
> > +static inline long atomic_long_read##mo##suffix(const atomic_long##suffix##_t *l)\
> > { \
> > - ATOMIC_LONG_PFX(_t) *v = (ATOMIC_LONG_PFX(_t) *)l; \
> > + ATOMIC_LONG_PFX(suffix##_t) *v = (ATOMIC_LONG_PFX(suffix##_t) *)l;\
> > \
> > - return (long)ATOMIC_LONG_PFX(_read##mo)(v); \
> > + return (long)ATOMIC_LONG_PFX(_read##mo##suffix)(v); \
> > }
> > -ATOMIC_LONG_READ_OP()
> > -ATOMIC_LONG_READ_OP(_acquire)
> > +ATOMIC_LONG_READ_OP(,)
> > +ATOMIC_LONG_READ_OP(_acquire,)
> > +
> > +#ifdef CONFIG_HARDENED_ATOMIC
> > +ATOMIC_LONG_READ_OP(,_wrap)
> > +#else /* CONFIG_HARDENED_ATOMIC */
> > +#define atomic_long_read_wrap(v) atomic_long_read((v))
> > +#endif /* CONFIG_HARDENED_ATOMIC */
> >
> > #undef ATOMIC_LONG_READ_OP
> >
> > -#define ATOMIC_LONG_SET_OP(mo) \
> > -static inline void atomic_long_set##mo(atomic_long_t *l, long i) \
> > +#define ATOMIC_LONG_SET_OP(mo, suffix) \
> > +static inline void atomic_long_set##mo##suffix(atomic_long##suffix##_t *l, long i)\
> > { \
> > - ATOMIC_LONG_PFX(_t) *v = (ATOMIC_LONG_PFX(_t) *)l; \
> > + ATOMIC_LONG_PFX(suffix##_t) *v = (ATOMIC_LONG_PFX(suffix##_t) *)l;\
> > \
> > - ATOMIC_LONG_PFX(_set##mo)(v, i); \
> > + ATOMIC_LONG_PFX(_set##mo##suffix)(v, i); \
> > }
> > -ATOMIC_LONG_SET_OP()
> > -ATOMIC_LONG_SET_OP(_release)
> > +ATOMIC_LONG_SET_OP(,)
> > +ATOMIC_LONG_SET_OP(_release,)
> > +
> > +#ifdef CONFIG_HARDENED_ATOMIC
> > +ATOMIC_LONG_SET_OP(,_wrap)
> > +#else /* CONFIG_HARDENED_ATOMIC */
> > +#define atomic_long_set_wrap(v, i) atomic_long_set((v), (i))
> > +#endif /* CONFIG_HARDENED_ATOMIC */
> >
> > #undef ATOMIC_LONG_SET_OP
> >
> > -#define ATOMIC_LONG_ADD_SUB_OP(op, mo) \
> > +#define ATOMIC_LONG_ADD_SUB_OP(op, mo, suffix) \
> > static inline long \
> > -atomic_long_##op##_return##mo(long i, atomic_long_t *l) \
> > +atomic_long_##op##_return##mo##suffix(long i, atomic_long##suffix##_t *l)\
> > { \
> > - ATOMIC_LONG_PFX(_t) *v = (ATOMIC_LONG_PFX(_t) *)l; \
> > + ATOMIC_LONG_PFX(suffix##_t) *v = (ATOMIC_LONG_PFX(suffix##_t) *)l;\
> > \
> > - return (long)ATOMIC_LONG_PFX(_##op##_return##mo)(i, v); \
> > + return (long)ATOMIC_LONG_PFX(_##op##_return##mo##suffix)(i, v);\
> > }
> > -ATOMIC_LONG_ADD_SUB_OP(add,)
> > -ATOMIC_LONG_ADD_SUB_OP(add, _relaxed)
> > -ATOMIC_LONG_ADD_SUB_OP(add, _acquire)
> > -ATOMIC_LONG_ADD_SUB_OP(add, _release)
> > -ATOMIC_LONG_ADD_SUB_OP(sub,)
> > -ATOMIC_LONG_ADD_SUB_OP(sub, _relaxed)
> > -ATOMIC_LONG_ADD_SUB_OP(sub, _acquire)
> > -ATOMIC_LONG_ADD_SUB_OP(sub, _release)
> > +ATOMIC_LONG_ADD_SUB_OP(add,,)
> > +ATOMIC_LONG_ADD_SUB_OP(add, _relaxed,)
> > +ATOMIC_LONG_ADD_SUB_OP(add, _acquire,)
> > +ATOMIC_LONG_ADD_SUB_OP(add, _release,)
> > +ATOMIC_LONG_ADD_SUB_OP(sub,,)
> > +ATOMIC_LONG_ADD_SUB_OP(sub, _relaxed,)
> > +ATOMIC_LONG_ADD_SUB_OP(sub, _acquire,)
> > +ATOMIC_LONG_ADD_SUB_OP(sub, _release,)
> > +
> > +#ifdef CONFIG_HARDENED_ATOMIC
> > +ATOMIC_LONG_ADD_SUB_OP(add,,_wrap)
> > +ATOMIC_LONG_ADD_SUB_OP(sub,,_wrap)
> > +#else /* CONFIG_HARDENED_ATOMIC */
> > +#define atomic_long_add_return_wrap(i,v) atomic_long_add_return((i), (v))
> > +#define atomic_long_sub_return_wrap(i,v) atomic_long_sub_return((i), (v))
> > +#endif /* CONFIG_HARDENED_ATOMIC */
> >
> > #undef ATOMIC_LONG_ADD_SUB_OP
> >
> > @@ -89,6 +121,13 @@ ATOMIC_LONG_ADD_SUB_OP(sub, _release)
> > #define atomic_long_cmpxchg(l, old, new) \
> > (ATOMIC_LONG_PFX(_cmpxchg)((ATOMIC_LONG_PFX(_t) *)(l), (old), (new)))
> >
> > +#ifdef CONFIG_HARDENED_ATOMIC
> > +#define atomic_long_cmpxchg_wrap(l, old, new) \
> > + (ATOMIC_LONG_PFX(_cmpxchg_wrap)((ATOMIC_LONG_PFX(_wrap_t) *)(l), (old), (new)))
> > +#else /* CONFIG_HARDENED_ATOMIC */
> > +#define atomic_long_cmpxchg_wrap(v, o, n) atomic_long_cmpxchg((v), (o), (n))
> > +#endif /* CONFIG_HARDENED_ATOMIC */
> > +
> > #define atomic_long_xchg_relaxed(v, new) \
> > (ATOMIC_LONG_PFX(_xchg_relaxed)((ATOMIC_LONG_PFX(_t) *)(v), (new)))
> > #define atomic_long_xchg_acquire(v, new) \
> > @@ -98,6 +137,13 @@ ATOMIC_LONG_ADD_SUB_OP(sub, _release)
> > #define atomic_long_xchg(v, new) \
> > (ATOMIC_LONG_PFX(_xchg)((ATOMIC_LONG_PFX(_t) *)(v), (new)))
> >
> > +#ifdef CONFIG_HARDENED_ATOMIC
> > +#define atomic_long_xchg_wrap(v, new) \
> > + (ATOMIC_LONG_PFX(_xchg_wrap)((ATOMIC_LONG_PFX(_wrap_t) *)(v), (new)))
> > +#else /* CONFIG_HARDENED_ATOMIC */
> > +#define atomic_long_xchg_wrap(v, i) atomic_long_xchg((v), (i))
> > +#endif /* CONFIG_HARDENED_ATOMIC */
> > +
> > static __always_inline void atomic_long_inc(atomic_long_t *l)
> > {
> > ATOMIC_LONG_PFX(_t) *v = (ATOMIC_LONG_PFX(_t) *)l;
> > @@ -105,6 +151,17 @@ static __always_inline void atomic_long_inc(atomic_long_t *l)
> > ATOMIC_LONG_PFX(_inc)(v);
> > }
> >
> > +#ifdef CONFIG_HARDENED_ATOMIC
> > +static __always_inline void atomic_long_inc_wrap(atomic_long_wrap_t *l)
> > +{
> > + ATOMIC_LONG_PFX(_wrap_t) *v = (ATOMIC_LONG_PFX(_wrap_t) *)l;
> > +
> > + ATOMIC_LONG_PFX(_inc_wrap)(v);
> > +}
> > +#else
> > +#define atomic_long_inc_wrap(v) atomic_long_inc(v)
> > +#endif
> > +
> > static __always_inline void atomic_long_dec(atomic_long_t *l)
> > {
> > ATOMIC_LONG_PFX(_t) *v = (ATOMIC_LONG_PFX(_t) *)l;
> > @@ -112,6 +169,17 @@ static __always_inline void atomic_long_dec(atomic_long_t *l)
> > ATOMIC_LONG_PFX(_dec)(v);
> > }
> >
> > +#ifdef CONFIG_HARDENED_ATOMIC
> > +static __always_inline void atomic_long_dec_wrap(atomic_long_wrap_t *l)
> > +{
> > + ATOMIC_LONG_PFX(_wrap_t) *v = (ATOMIC_LONG_PFX(_wrap_t) *)l;
> > +
> > + ATOMIC_LONG_PFX(_dec_wrap)(v);
> > +}
> > +#else
> > +#define atomic_long_dec_wrap(v) atomic_long_dec(v)
> > +#endif
> > +
> > #define ATOMIC_LONG_FETCH_OP(op, mo) \
> > static inline long \
> > atomic_long_fetch_##op##mo(long i, atomic_long_t *l) \
> > @@ -168,21 +236,29 @@ ATOMIC_LONG_FETCH_INC_DEC_OP(dec, _release)
> >
> > #undef ATOMIC_LONG_FETCH_INC_DEC_OP
> >
> > -#define ATOMIC_LONG_OP(op) \
> > +#define ATOMIC_LONG_OP(op, suffix) \
> > static __always_inline void \
> > -atomic_long_##op(long i, atomic_long_t *l) \
> > +atomic_long_##op##suffix(long i, atomic_long##suffix##_t *l) \
> > { \
> > - ATOMIC_LONG_PFX(_t) *v = (ATOMIC_LONG_PFX(_t) *)l; \
> > + ATOMIC_LONG_PFX(suffix##_t) *v = (ATOMIC_LONG_PFX(suffix##_t) *)l;\
> > \
> > - ATOMIC_LONG_PFX(_##op)(i, v); \
> > + ATOMIC_LONG_PFX(_##op##suffix)(i, v); \
> > }
> >
> > -ATOMIC_LONG_OP(add)
> > -ATOMIC_LONG_OP(sub)
> > -ATOMIC_LONG_OP(and)
> > -ATOMIC_LONG_OP(andnot)
> > -ATOMIC_LONG_OP(or)
> > -ATOMIC_LONG_OP(xor)
> > +ATOMIC_LONG_OP(add,)
> > +ATOMIC_LONG_OP(sub,)
> > +ATOMIC_LONG_OP(and,)
> > +ATOMIC_LONG_OP(or,)
> > +ATOMIC_LONG_OP(xor,)
> > +ATOMIC_LONG_OP(andnot,)
> > +
> > +#ifdef CONFIG_HARDENED_ATOMIC
> > +ATOMIC_LONG_OP(add,_wrap)
> > +ATOMIC_LONG_OP(sub,_wrap)
> > +#else /* CONFIG_HARDENED_ATOMIC */
> > +#define atomic_long_add_wrap(i,v) atomic_long_add((i),(v))
> > +#define atomic_long_sub_wrap(i,v) atomic_long_sub((i),(v))
> > +#endif /* CONFIG_HARDENED_ATOMIC */
> >
> > #undef ATOMIC_LONG_OP
> >
> > @@ -193,6 +269,15 @@ static inline int atomic_long_sub_and_test(long i, atomic_long_t *l)
> > return ATOMIC_LONG_PFX(_sub_and_test)(i, v);
> > }
> >
> > +/*
> > +static inline int atomic_long_add_and_test(long i, atomic_long_t *l)
> > +{
> > + ATOMIC_LONG_PFX(_t) *v = (ATOMIC_LONG_PFX(_t) *)l;
> > +
> > + return ATOMIC_LONG_PFX(_add_and_test)(i, v);
> > +}
> > +*/
> > +
> > static inline int atomic_long_dec_and_test(atomic_long_t *l)
> > {
> > ATOMIC_LONG_PFX(_t) *v = (ATOMIC_LONG_PFX(_t) *)l;
> > @@ -214,22 +299,75 @@ static inline int atomic_long_add_negative(long i, atomic_long_t *l)
> > return ATOMIC_LONG_PFX(_add_negative)(i, v);
> > }
> >
> > -#define ATOMIC_LONG_INC_DEC_OP(op, mo) \
> > +#ifdef CONFIG_HARDENED_ATOMIC
> > +static inline int atomic_long_sub_and_test_wrap(long i, atomic_long_wrap_t *l)
> > +{
> > + ATOMIC_LONG_PFX(_wrap_t) *v = (ATOMIC_LONG_PFX(_wrap_t) *)l;
> > +
> > + return ATOMIC_LONG_PFX(_sub_and_test_wrap)(i, v);
> > +}
> > +
> > +
> > +static inline int atomic_long_add_and_test_wrap(long i, atomic_long_wrap_t *l)
> > +{
> > + ATOMIC_LONG_PFX(_wrap_t) *v = (ATOMIC_LONG_PFX(_wrap_t) *)l;
> > +
> > + return ATOMIC_LONG_PFX(_add_and_test_wrap)(i, v);
> > +}
>
> This definition should be removed as atomic_add_and_test() above
> since atomic*_add_and_test() are not defined.
The *_add_and_test* functionew were intentionally added for function coverage.
The idea was to make that the *_sub_and_test* functions have corresponding add
function, but maybe this was misguided?
It might indeed be better to restrict the function coverage efforts to providing
_wrap versions?
>
> > +
> > +
> > +static inline int atomic_long_dec_and_test_wrap(atomic_long_wrap_t *l)
> > +{
> > + ATOMIC_LONG_PFX(_wrap_t) *v = (ATOMIC_LONG_PFX(_wrap_t) *)l;
> > +
> > + return ATOMIC_LONG_PFX(_dec_and_test_wrap)(v);
> > +}
> > +
> > +static inline int atomic_long_inc_and_test_wrap(atomic_long_wrap_t *l)
> > +{
> > + ATOMIC_LONG_PFX(_wrap_t) *v = (ATOMIC_LONG_PFX(_wrap_t) *)l;
> > +
> > + return ATOMIC_LONG_PFX(_inc_and_test_wrap)(v);
> > +}
> > +
> > +static inline int atomic_long_add_negative_wrap(long i, atomic_long_wrap_t *l)
> > +{
> > + ATOMIC_LONG_PFX(_wrap_t) *v = (ATOMIC_LONG_PFX(_wrap_t) *)l;
> > +
> > + return ATOMIC_LONG_PFX(_add_negative_wrap)(i, v);
> > +}
> > +#else /* CONFIG_HARDENED_ATOMIC */
> > +#define atomic_long_sub_and_test_wrap(i, v) atomic_long_sub_and_test((i), (v))
> > +#define atomic_long_add_and_test_wrap(i, v) atomic_long_add_and_test((i), (v))
> > +#define atomic_long_dec_and_test_wrap(i, v) atomic_long_dec_and_test((i), (v))
> > +#define atomic_long_inc_and_test_wrap(i, v) atomic_long_inc_and_test((i), (v))
> > +#define atomic_long_add_negative_wrap(i, v) atomic_long_add_negative((i), (v))
> > +#endif /* CONFIG_HARDENED_ATOMIC */
> > +
> > +#define ATOMIC_LONG_INC_DEC_OP(op, mo, suffix) \
> > static inline long \
> > -atomic_long_##op##_return##mo(atomic_long_t *l) \
> > +atomic_long_##op##_return##mo##suffix(atomic_long##suffix##_t *l) \
> > { \
> > - ATOMIC_LONG_PFX(_t) *v = (ATOMIC_LONG_PFX(_t) *)l; \
> > + ATOMIC_LONG_PFX(suffix##_t) *v = (ATOMIC_LONG_PFX(suffix##_t) *)l;\
> > \
> > - return (long)ATOMIC_LONG_PFX(_##op##_return##mo)(v); \
> > + return (long)ATOMIC_LONG_PFX(_##op##_return##mo##suffix)(v); \
> > }
> > -ATOMIC_LONG_INC_DEC_OP(inc,)
> > -ATOMIC_LONG_INC_DEC_OP(inc, _relaxed)
> > -ATOMIC_LONG_INC_DEC_OP(inc, _acquire)
> > -ATOMIC_LONG_INC_DEC_OP(inc, _release)
> > -ATOMIC_LONG_INC_DEC_OP(dec,)
> > -ATOMIC_LONG_INC_DEC_OP(dec, _relaxed)
> > -ATOMIC_LONG_INC_DEC_OP(dec, _acquire)
> > -ATOMIC_LONG_INC_DEC_OP(dec, _release)
> > +ATOMIC_LONG_INC_DEC_OP(inc,,)
> > +ATOMIC_LONG_INC_DEC_OP(inc, _relaxed,)
> > +ATOMIC_LONG_INC_DEC_OP(inc, _acquire,)
> > +ATOMIC_LONG_INC_DEC_OP(inc, _release,)
> > +ATOMIC_LONG_INC_DEC_OP(dec,,)
> > +ATOMIC_LONG_INC_DEC_OP(dec, _relaxed,)
> > +ATOMIC_LONG_INC_DEC_OP(dec, _acquire,)
> > +ATOMIC_LONG_INC_DEC_OP(dec, _release,)
> > +
> > +#ifdef CONFIG_HARDENED_ATOMIC
> > +ATOMIC_LONG_INC_DEC_OP(inc,,_wrap)
> > +ATOMIC_LONG_INC_DEC_OP(dec,,_wrap)
> > +#else /* CONFIG_HARDENED_ATOMIC */
> > +#define atomic_long_inc_return_wrap(v) atomic_long_inc_return((v))
> > +#define atomic_long_dec_return_wrap(v) atomic_long_dec_return((v))
> > +#endif /* CONFIG_HARDENED_ATOMIC */
> >
> > #undef ATOMIC_LONG_INC_DEC_OP
> >
> > @@ -240,7 +378,41 @@ static inline long atomic_long_add_unless(atomic_long_t *l, long a, long u)
> > return (long)ATOMIC_LONG_PFX(_add_unless)(v, a, u);
> > }
> >
> > +#ifdef CONFIG_HARDENED_ATOMIC
> > +static inline long atomic_long_add_unless_wrap(atomic_long_wrap_t *l, long a, long u)
> > +{
> > + ATOMIC_LONG_PFX(_wrap_t) *v = (ATOMIC_LONG_PFX(_wrap_t) *)l;
> > +
> > + return (long)ATOMIC_LONG_PFX(_add_unless_wrap)(v, a, u);
> > +}
> > +#else /* CONFIG_HARDENED_ATOMIC */
> > +#define atomic_long_add_unless_wrap(v, i, j) atomic_long_add_unless((v), (i), (j))
> > +#endif /* CONFIG_HARDENED_ATOMIC */
> > +
> > #define atomic_long_inc_not_zero(l) \
> > ATOMIC_LONG_PFX(_inc_not_zero)((ATOMIC_LONG_PFX(_t) *)(l))
> >
> > +#ifndef CONFIG_HARDENED_ATOMIC
> > +#define atomic_read_wrap(v) atomic_read(v)
> > +#define atomic_set_wrap(v, i) atomic_set((v), (i))
> > +#define atomic_add_wrap(i, v) atomic_add((i), (v))
> > +#define atomic_sub_wrap(i, v) atomic_sub((i), (v))
> > +#define atomic_inc_wrap(v) atomic_inc(v)
> > +#define atomic_dec_wrap(v) atomic_dec(v)
> > +#define atomic_add_return_wrap(i, v) atomic_add_return((i), (v))
> > +#define atomic_sub_return_wrap(i, v) atomic_sub_return((i), (v))
> > +#define atoimc_dec_return_wrap(v) atomic_dec_return(v)
> > +#ifndef atomic_inc_return_wrap
> > +#define atomic_inc_return_wrap(v) atomic_inc_return(v)
> > +#endif /* atomic_inc_return */
> > +#define atomic_dec_and_test_wrap(v) atomic_dec_and_test(v)
> > +#define atomic_inc_and_test_wrap(v) atomic_inc_and_test(v)
> > +#define atomic_add_and_test_wrap(i, v) atomic_add_and_test((v), (i))
> > +#define atomic_sub_and_test_wrap(i, v) atomic_sub_and_test((v), (i))
> > +#define atomic_xchg_wrap(v, i) atomic_xchg((v), (i))
> > +#define atomic_cmpxchg_wrap(v, o, n) atomic_cmpxchg((v), (o), (n))
> > +#define atomic_add_negative_wrap(i, v) atomic_add_negative((i), (v))
> > +#define atomic_add_unless_wrap(v, i, j) atomic_add_unless((v), (i), (j))
> > +#endif /* CONFIG_HARDENED_ATOMIC */
> > +
> > #endif /* _ASM_GENERIC_ATOMIC_LONG_H */
> > diff --git a/include/asm-generic/atomic.h b/include/asm-generic/atomic.h
> > index 9ed8b98..6c3ed48 100644
> > --- a/include/asm-generic/atomic.h
> > +++ b/include/asm-generic/atomic.h
> > @@ -177,6 +177,10 @@ ATOMIC_OP(xor, ^)
> > #define atomic_read(v) READ_ONCE((v)->counter)
> > #endif
> >
> > +#ifndef atomic_read_wrap
> > +#define atomic_read_wrap(v) READ_ONCE((v)->counter)
> > +#endif
> > +
> > /**
> > * atomic_set - set atomic variable
> > * @v: pointer of type atomic_t
> > @@ -186,6 +190,10 @@ ATOMIC_OP(xor, ^)
> > */
> > #define atomic_set(v, i) WRITE_ONCE(((v)->counter), (i))
> >
> > +#ifndef atomic_set_wrap
> > +#define atomic_set_wrap(v, i) WRITE_ONCE(((v)->counter), (i))
> > +#endif
> > +
> > #include <linux/irqflags.h>
> >
> > static inline int atomic_add_negative(int i, atomic_t *v)
> > @@ -193,33 +201,72 @@ static inline int atomic_add_negative(int i, atomic_t *v)
> > return atomic_add_return(i, v) < 0;
> > }
> >
> > +static inline int atomic_add_negative_wrap(int i, atomic_wrap_t *v)
> > +{
> > + return atomic_add_return_wrap(i, v) < 0;
> > +}
> > +
> > static inline void atomic_add(int i, atomic_t *v)
> > {
> > atomic_add_return(i, v);
> > }
> >
> > +static inline void atomic_add_wrap(int i, atomic_wrap_t *v)
> > +{
> > + atomic_add_return_wrap(i, v);
> > +}
> > +
> > static inline void atomic_sub(int i, atomic_t *v)
> > {
> > atomic_sub_return(i, v);
> > }
> >
> > +static inline void atomic_sub_wrap(int i, atomic_wrap_t *v)
> > +{
> > + atomic_sub_return_wrap(i, v);
> > +}
> > +
> > static inline void atomic_inc(atomic_t *v)
> > {
> > atomic_add_return(1, v);
> > }
> >
> > +static inline void atomic_inc_wrap(atomic_wrap_t *v)
> > +{
> > + atomic_add_return_wrap(1, v);
> > +}
> > +
> > static inline void atomic_dec(atomic_t *v)
> > {
> > atomic_sub_return(1, v);
> > }
> >
> > +static inline void atomic_dec_wrap(atomic_wrap_t *v)
> > +{
> > + atomic_sub_return_wrap(1, v);
> > +}
> > +
> > #define atomic_dec_return(v) atomic_sub_return(1, (v))
> > #define atomic_inc_return(v) atomic_add_return(1, (v))
> >
> > +#define atomic_add_and_test(i, v) (atomic_add_return((i), (v)) == 0)
> > #define atomic_sub_and_test(i, v) (atomic_sub_return((i), (v)) == 0)
> > #define atomic_dec_and_test(v) (atomic_dec_return(v) == 0)
> > #define atomic_inc_and_test(v) (atomic_inc_return(v) == 0)
> >
> > +#ifndef atomic_add_and_test_wrap
> > +#define atomic_add_and_test_wrap(i, v) (atomic_add_return_wrap((i), (v)) == 0)
> > +#endif
> > +#ifndef atomic_sub_and_test_wrap
> > +#define atomic_sub_and_test_wrap(i, v) (atomic_sub_return_wrap((i), (v)) == 0)
> > +#endif
> > +#ifndef atomic_dec_and_test_wrap
> > +#define atomic_dec_and_test_wrap(v) (atomic_dec_return_wrap(v) == 0)
> > +#endif
> > +#ifndef atomic_inc_and_test_wrap
> > +#define atomic_inc_and_test_wrap(v) (atomic_inc_return_wrap(v) == 0)
> > +#endif
> > +
> > #define atomic_xchg(ptr, v) (xchg(&(ptr)->counter, (v)))
> > #define atomic_cmpxchg(v, old, new) (cmpxchg(&((v)->counter), (old), (new)))
> >
> > @@ -232,4 +279,13 @@ static inline int __atomic_add_unless(atomic_t *v, int a, int u)
> > return c;
> > }
> >
> > +static inline int __atomic_add_unless_wrap(atomic_wrap_t *v, int a, int u)
> > +{
> > + int c, old;
> > + c = atomic_read_wrap(v);
> > + while (c != u && (old = atomic_cmpxchg_wrap(v, c, c + a)) != c)
> > + c = old;
> > + return c;
> > +}
> > +
> > #endif /* __ASM_GENERIC_ATOMIC_H */
> > diff --git a/include/asm-generic/atomic64.h b/include/asm-generic/atomic64.h
> > index dad68bf..0bb63b9 100644
> > --- a/include/asm-generic/atomic64.h
> > +++ b/include/asm-generic/atomic64.h
> > @@ -56,10 +56,23 @@ extern int atomic64_add_unless(atomic64_t *v, long long a, long long u);
> > #define atomic64_inc(v) atomic64_add(1LL, (v))
> > #define atomic64_inc_return(v) atomic64_add_return(1LL, (v))
> > #define atomic64_inc_and_test(v) (atomic64_inc_return(v) == 0)
> > +#define atomic64_add_and_test(a, v) (atomic64_add_return((a), (v)) == 0)
> > #define atomic64_sub_and_test(a, v) (atomic64_sub_return((a), (v)) == 0)
> > #define atomic64_dec(v) atomic64_sub(1LL, (v))
> > #define atomic64_dec_return(v) atomic64_sub_return(1LL, (v))
> > #define atomic64_dec_and_test(v) (atomic64_dec_return((v)) == 0)
> > #define atomic64_inc_not_zero(v) atomic64_add_unless((v), 1LL, 0LL)
> >
> > +#define atomic64_read_wrap(v) atomic64_read(v)
> > +#define atomic64_set_wrap(v, i) atomic64_set((v), (i))
> > +#define atomic64_add_wrap(a, v) atomic64_add((a), (v))
> > +#define atomic64_add_return_wrap(a, v) atomic64_add_return((a), (v))
> > +#define atomic64_sub_wrap(a, v) atomic64_sub((a), (v))
> > +#define atomic64_inc_wrap(v) atomic64_inc(v)
> > +#define atomic64_inc_return_wrap(v) atomic64_inc_return(v)
> > +#define atomic64_dec_wrap(v) atomic64_dec(v)
> > +#define atomic64_dec_return_wrap(v) atomic64_return_dec(v)
> > +#define atomic64_cmpxchg_wrap(v, o, n) atomic64_cmpxchg((v), (o), (n))
> > +#define atomic64_xchg_wrap(v, n) atomic64_xchg((v), (n))
> > +
> > #endif /* _ASM_GENERIC_ATOMIC64_H */
> > diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h
> > index 6f96247..20ce604 100644
> > --- a/include/asm-generic/bug.h
> > +++ b/include/asm-generic/bug.h
> > @@ -215,6 +215,13 @@ void __warn(const char *file, int line, void *caller, unsigned taint,
> > # define WARN_ON_SMP(x) ({0;})
> > #endif
> >
> > +#ifdef CONFIG_HARDENED_ATOMIC
> > +void hardened_atomic_overflow(struct pt_regs *regs);
> > +#else
> > +static inline void hardened_atomic_overflow(struct pt_regs *regs){
> > +}
> > +#endif
> > +
> > #endif /* __ASSEMBLY__ */
> >
> > #endif
> > diff --git a/include/asm-generic/local.h b/include/asm-generic/local.h
> > index 9ceb03b..a98ad1d 100644
> > --- a/include/asm-generic/local.h
> > +++ b/include/asm-generic/local.h
> > @@ -23,24 +23,39 @@ typedef struct
> > atomic_long_t a;
> > } local_t;
> >
> > +typedef struct {
> > + atomic_long_wrap_t a;
> > +} local_wrap_t;
> > +
> > #define LOCAL_INIT(i) { ATOMIC_LONG_INIT(i) }
> >
> > #define local_read(l) atomic_long_read(&(l)->a)
> > +#define local_read_wrap(l) atomic_long_read_wrap(&(l)->a)
> > #define local_set(l,i) atomic_long_set((&(l)->a),(i))
> > +#define local_set_wrap(l,i) atomic_long_set_wrap((&(l)->a),(i))
> > #define local_inc(l) atomic_long_inc(&(l)->a)
> > +#define local_inc_wrap(l) atomic_long_inc_wrap(&(l)->a)
> > #define local_dec(l) atomic_long_dec(&(l)->a)
> > +#define local_dec_wrap(l) atomic_long_dec_wrap(&(l)->a)
> > #define local_add(i,l) atomic_long_add((i),(&(l)->a))
> > +#define local_add_wrap(i,l) atomic_long_add_wrap((i),(&(l)->a))
> > #define local_sub(i,l) atomic_long_sub((i),(&(l)->a))
> > +#define local_sub_wrap(i,l) atomic_long_sub_wrap((i),(&(l)->a))
> >
> > #define local_sub_and_test(i, l) atomic_long_sub_and_test((i), (&(l)->a))
> > +#define local_sub_and_test_wrap(i, l) atomic_long_sub_and_test_wrap((i), (&(l)->a))
> > #define local_dec_and_test(l) atomic_long_dec_and_test(&(l)->a)
> > #define local_inc_and_test(l) atomic_long_inc_and_test(&(l)->a)
> > #define local_add_negative(i, l) atomic_long_add_negative((i), (&(l)->a))
> > #define local_add_return(i, l) atomic_long_add_return((i), (&(l)->a))
> > +#define local_add_return_wrap(i, l) atomic_long_add_return_wrap((i), (&(l)->a))
> > #define local_sub_return(i, l) atomic_long_sub_return((i), (&(l)->a))
> > #define local_inc_return(l) atomic_long_inc_return(&(l)->a)
> > +/* verify that below function is needed */
> > +#define local_dec_return(l) atomic_long_dec_return(&(l)->a)
> >
> > #define local_cmpxchg(l, o, n) atomic_long_cmpxchg((&(l)->a), (o), (n))
> > +#define local_cmpxchg_wrap(l, o, n) atomic_long_cmpxchg_wrap((&(l)->a), (o), (n))
> > #define local_xchg(l, n) atomic_long_xchg((&(l)->a), (n))
> > #define local_add_unless(l, _a, u) atomic_long_add_unless((&(l)->a), (_a), (u))
> > #define local_inc_not_zero(l) atomic_long_inc_not_zero(&(l)->a)
> > diff --git a/include/linux/atomic.h b/include/linux/atomic.h
> > index e71835b..3cb48f0 100644
> > --- a/include/linux/atomic.h
> > +++ b/include/linux/atomic.h
> > @@ -89,6 +89,11 @@
> > #define atomic_add_return(...) \
> > __atomic_op_fence(atomic_add_return, __VA_ARGS__)
> > #endif
> > +
> > +#ifndef atomic_add_return_wrap
> > +#define atomic_add_return_wrap(...) \
> > + __atomic_op_fence(atomic_add_return_wrap, __VA_ARGS__)
> > +#endif
> > #endif /* atomic_add_return_relaxed */
> >
> > /* atomic_inc_return_relaxed */
> > @@ -113,6 +118,11 @@
> > #define atomic_inc_return(...) \
> > __atomic_op_fence(atomic_inc_return, __VA_ARGS__)
> > #endif
> > +
> > +#ifndef atomic_inc_return_wrap
> > +#define atomic_inc_return_wrap(...) \
> > + __atomic_op_fence(atomic_inc_return_wrap, __VA_ARGS__)
> > +#endif
> > #endif /* atomic_inc_return_relaxed */
> >
> > /* atomic_sub_return_relaxed */
> > @@ -137,6 +147,11 @@
> > #define atomic_sub_return(...) \
> > __atomic_op_fence(atomic_sub_return, __VA_ARGS__)
> > #endif
> > +
> > +#ifndef atomic_sub_return_wrap
> > +#define atomic_sub_return_wrap(...) \
> > + __atomic_op_fence(atomic_sub_return_wrap, __VA_ARGS__)
> > +#endif
> > #endif /* atomic_sub_return_relaxed */
> >
> > /* atomic_dec_return_relaxed */
> > @@ -161,6 +176,11 @@
> > #define atomic_dec_return(...) \
> > __atomic_op_fence(atomic_dec_return, __VA_ARGS__)
> > #endif
> > +
> > +#ifndef atomic_dec_return_wrap
> > +#define atomic_dec_return_wrap(...) \
> > + __atomic_op_fence(atomic_dec_return_wrap, __VA_ARGS__)
> > +#endif
> > #endif /* atomic_dec_return_relaxed */
> >
> >
> > @@ -397,6 +417,11 @@
> > #define atomic_xchg(...) \
> > __atomic_op_fence(atomic_xchg, __VA_ARGS__)
> > #endif
> > +
> > +#ifndef atomic_xchg_wrap
> > +#define atomic_xchg_wrap(...) \
> > + _atomic_op_fence(atomic_xchg_wrap, __VA_ARGS__)
> > +#endif
> > #endif /* atomic_xchg_relaxed */
> >
> > /* atomic_cmpxchg_relaxed */
> > @@ -421,6 +446,11 @@
> > #define atomic_cmpxchg(...) \
> > __atomic_op_fence(atomic_cmpxchg, __VA_ARGS__)
> > #endif
> > +
> > +#ifndef atomic_cmpxchg_wrap
> > +#define atomic_cmpxchg_wrap(...) \
> > + _atomic_op_fence(atomic_cmpxchg_wrap, __VA_ARGS__)
> > +#endif
> > #endif /* atomic_cmpxchg_relaxed */
> >
> > /* cmpxchg_relaxed */
> > @@ -507,6 +537,22 @@ static inline int atomic_add_unless(atomic_t *v, int a, int u)
> > }
> >
> > /**
> > + * atomic_add_unless_wrap - add unless the number is already a given value
> > + * @v: pointer of type atomic_wrap_t
> > + * @a: the amount to add to v...
> > + * @u: ...unless v is equal to u.
> > + *
> > + * Atomically adds @a to @v, so long as @v was not already @u.
> > + * Returns non-zero if @v was not @u, and zero otherwise.
> > + */
> > +#ifdef CONFIG_HARDENED_ATOMIC
> > +static inline int atomic_add_unless_wrap(atomic_wrap_t *v, int a, int u)
> > +{
> > + return __atomic_add_unless_wrap(v, a, u) != u;
> > +}
> > +#endif /* CONFIG_HARDENED_ATOMIC */
> > +
> > +/**
> > * atomic_inc_not_zero - increment unless the number is zero
> > * @v: pointer of type atomic_t
> > *
> > @@ -631,6 +677,43 @@ static inline int atomic_dec_if_positive(atomic_t *v)
> > #include <asm-generic/atomic64.h>
> > #endif
> >
> > +#ifndef CONFIG_HARDENED_ATOMIC
> > +#define atomic64_wrap_t atomic64_t
> > +#ifndef atomic64_read_wrap
> > +#define atomic64_read_wrap(v) atomic64_read(v)
> > +#endif
> > +#ifndef atomic64_set_wrap
> > +#define atomic64_set_wrap(v, i) atomic64_set((v), (i))
> > +#endif
> > +#ifndef atomic64_add_wrap
> > +#define atomic64_add_wrap(a, v) atomic64_add((a), (v))
> > +#endif
> > +#ifndef atomic64_add_return_wrap
> > +#define atomic64_add_return_wrap(a, v) atomic64_add_return((a), (v))
> > +#endif
> > +#ifndef atomic64_sub_wrap
> > +#define atomic64_sub_wrap(a, v) atomic64_sub((a), (v))
> > +#endif
> > +#ifndef atomic64_inc_wrap
> > +#define atomic64_inc_wrap(v) atomic64_inc((v))
> > +#endif
> > +#ifndef atomic64_inc_return_wrap
> > +#define atomic64_inc_return_wrap(v) atomic64_inc_return((v))
> > +#endif
> > +#ifndef atomic64_dec_wrap
> > +#define atomic64_dec_wrap(v) atomic64_dec((v))
> > +#endif
> > +#ifndef atomic64_dec_return_wrap
> > +#define atomic64_dec_return_wrap(v) atomic64_dec_return((v))
> > +#endif
> > +#ifndef atomic64_cmpxchg_wrap
> > +#define atomic64_cmpxchg_wrap(v, o, n) atomic64_cmpxchg((v), (o), (n))
> > +#endif
> > +#ifndef atomic64_xchg_wrap
> > +#define atomic64_xchg_wrap(v, n) atomic64_xchg((v), (n))
> > +#endif
> > +#endif /* CONFIG_HARDENED_ATOMIC */
> > +
> > #ifndef atomic64_read_acquire
> > #define atomic64_read_acquire(v) smp_load_acquire(&(v)->counter)
> > #endif
> > @@ -661,6 +744,12 @@ static inline int atomic_dec_if_positive(atomic_t *v)
> > #define atomic64_add_return(...) \
> > __atomic_op_fence(atomic64_add_return, __VA_ARGS__)
> > #endif
> > +
> > +#ifndef atomic64_add_return_wrap
> > +#define atomic64_add_return_wrap(...) \
> > + __atomic_op_fence(atomic64_add_return_wrap, __VA_ARGS__)
> > +#endif
> > +
> > #endif /* atomic64_add_return_relaxed */
> >
> > /* atomic64_inc_return_relaxed */
> > @@ -685,6 +774,11 @@ static inline int atomic_dec_if_positive(atomic_t *v)
> > #define atomic64_inc_return(...) \
> > __atomic_op_fence(atomic64_inc_return, __VA_ARGS__)
> > #endif
> > +
> > +#ifndef atomic64_inc_return_wrap
> > +#define atomic64_inc_return_wrap(...) \
> > + __atomic_op_fence(atomic64_inc_return_wrap, __VA_ARGS__)
> > +#endif
> > #endif /* atomic64_inc_return_relaxed */
> >
> >
> > @@ -710,6 +804,11 @@ static inline int atomic_dec_if_positive(atomic_t *v)
> > #define atomic64_sub_return(...) \
> > __atomic_op_fence(atomic64_sub_return, __VA_ARGS__)
> > #endif
> > +
> > +#ifndef atomic64_sub_return_wrap
> > +#define atomic64_sub_return_wrap(...) \
> > + __atomic_op_fence(atomic64_sub_return_wrap, __VA_ARGS__)
> > +#endif
> > #endif /* atomic64_sub_return_relaxed */
> >
> > /* atomic64_dec_return_relaxed */
> > @@ -734,6 +833,11 @@ static inline int atomic_dec_if_positive(atomic_t *v)
> > #define atomic64_dec_return(...) \
> > __atomic_op_fence(atomic64_dec_return, __VA_ARGS__)
> > #endif
> > +
> > +#ifndef atomic64_dec_return_wrap
> > +#define atomic64_dec_return_wrap(...) \
> > + __atomic_op_fence(atomic64_dec_return_wrap, __VA_ARGS__)
> > +#endif
> > #endif /* atomic64_dec_return_relaxed */
> >
> >
> > @@ -970,6 +1074,11 @@ static inline int atomic_dec_if_positive(atomic_t *v)
> > #define atomic64_xchg(...) \
> > __atomic_op_fence(atomic64_xchg, __VA_ARGS__)
> > #endif
> > +
> > +#ifndef atomic64_xchg_wrap
> > +#define atomic64_xchg_wrap(...) \
> > + __atomic_op_fence(atomic64_xchg_wrap, __VA_ARGS__)
> > +#endif
> > #endif /* atomic64_xchg_relaxed */
> >
> > /* atomic64_cmpxchg_relaxed */
> > @@ -994,6 +1103,11 @@ static inline int atomic_dec_if_positive(atomic_t *v)
> > #define atomic64_cmpxchg(...) \
> > __atomic_op_fence(atomic64_cmpxchg, __VA_ARGS__)
> > #endif
> > +
> > +#ifndef atomic64_cmpxchg_wrap
> > +#define atomic64_cmpxchg_wrap(...) \
> > + __atomic_op_fence(atomic64_cmpxchg_wrap, __VA_ARGS__)
> > +#endif
> > #endif /* atomic64_cmpxchg_relaxed */
> >
> > #ifndef atomic64_andnot
> > diff --git a/include/linux/types.h b/include/linux/types.h
> > index baf7183..b47a7f8 100644
> > --- a/include/linux/types.h
> > +++ b/include/linux/types.h
> > @@ -175,10 +175,27 @@ typedef struct {
> > int counter;
> > } atomic_t;
> >
> > +#ifdef CONFIG_HARDENED_ATOMIC
> > +typedef struct {
> > + int counter;
> > +} atomic_wrap_t;
> > +#else
> > +typedef atomic_t atomic_wrap_t;
> > +#endif
> > +
> > #ifdef CONFIG_64BIT
> > typedef struct {
> > long counter;
> > } atomic64_t;
> > +
> > +#ifdef CONFIG_HARDENED_ATOMIC
> > +typedef struct {
> > + long counter;
> > +} atomic64_wrap_t;
> > +#else
> > +typedef atomic64_t atomic64_wrap_t;
> > +#endif
> > +
> > #endif
> >
> > struct list_head {
> > diff --git a/kernel/panic.c b/kernel/panic.c
> > index e6480e2..cb1d6db 100644
> > --- a/kernel/panic.c
> > +++ b/kernel/panic.c
> > @@ -616,3 +616,14 @@ static int __init oops_setup(char *s)
> > return 0;
> > }
> > early_param("oops", oops_setup);
> > +
> > +#ifdef CONFIG_HARDENED_ATOMIC
> > +void hardened_atomic_overflow(struct pt_regs *regs)
> > +{
> > + pr_emerg(KERN_EMERG "HARDENED_ATOMIC: overflow detected in: %s:%d, uid/euid: %u/%u\n",
> > + current->comm, task_pid_nr(current),
> > + from_kuid_munged(&init_user_ns, current_uid()),
> > + from_kuid_munged(&init_user_ns, current_euid()));
> > + BUG();
>
> BUG() will print a message like "kernel BUG at kernel/panic.c:627!"
> and a stack trace dump with extra frames including hardened_atomic_overflow()
> and some exception handler routines (do_trap() on x86), which are totally
> useless. So I don't want to call BUG() here.
>
> Instead, we will fall back to a normal "BUG" handler, bug_handler() on arm64,
> which eventually calls die(), generating more *intuitive* messages:
> ===8<===
> [ 29.082336] lkdtm: attempting good atomic_add_return
> [ 29.082391] lkdtm: attempting bad atomic_add_return
> [ 29.082830] ------------[ cut here ]------------
> [ 29.082889] Kernel BUG at ffff0000008b07fc [verbose debug info unavailable]
> (Actually, this is lkdtm_ATOMIC_ADD_RETURN_OVERFLOW)
> [ 29.082968] HARDENED_ATOMIC: overflow detected in: insmod:1152, uid/euid: 0/0
> [ 29.083043] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
> [ 29.083098] Modules linked in: lkdtm(+)
> [ 29.083189] CPU: 1 PID: 1152 Comm: insmod Not tainted 4.9.0-rc1-00024-gb757839-dirty #12
> [ 29.083262] Hardware name: FVP Base (DT)
> [ 29.083324] task: ffff80087aa21900 task.stack: ffff80087a36c000
> [ 29.083557] PC is at lkdtm_ATOMIC_ADD_RETURN_OVERFLOW+0x6c/0xa0 [lkdtm]
> [ 29.083627] LR is at 0x7fffffff
> [ 29.083687] pc : [<ffff0000008b07fc>] lr : [<000000007fffffff>] pstate: 90400149
> [ 29.083757] sp : ffff80087a36fbe0
> [ 29.083810] x29: ffff80087a36fbe0 [ 29.083858] x28: ffff000008ec3000
> [ 29.083906]
>
> ...
>
> [ 29.090842] [<ffff0000008b07fc>] lkdtm_ATOMIC_ADD_RETURN_OVERFLOW+0x6c/0xa0 [lkdtm]
> [ 29.091090] [<ffff0000008b20a4>] lkdtm_do_action+0x1c/0x28 [lkdtm]
> [ 29.091334] [<ffff0000008bb118>] lkdtm_module_init+0x118/0x210 [lkdtm]
> [ 29.091422] [<ffff000008083150>] do_one_initcall+0x38/0x128
> [ 29.091503] [<ffff000008166ad4>] do_init_module+0x5c/0x1c8
> [ 29.091586] [<ffff00000812e1ec>] load_module+0x1b24/0x20b0
> [ 29.091670] [<ffff00000812e920>] SyS_init_module+0x1a8/0x1d8
> [ 29.091753] [<ffff000008082ef0>] el0_svc_naked+0x24/0x28
> [ 29.091843] Code: 910063a1 b8e0003e 2b1e0010 540000c7 (d4210020)
> ===>8===
>
> Thanks,
> -Takahiro AKASHI
>
> > +}
> > +#endif
> > diff --git a/security/Kconfig b/security/Kconfig
> > index 118f454..abcf1cc 100644
> > --- a/security/Kconfig
> > +++ b/security/Kconfig
> > @@ -158,6 +158,25 @@ config HARDENED_USERCOPY_PAGESPAN
> > been removed. This config is intended to be used only while
> > trying to find such users.
> >
> > +config HAVE_ARCH_HARDENED_ATOMIC
> > + bool
> > + help
> > + The architecture supports CONFIG_HARDENED_ATOMIC by
> > + providing trapping on atomic_t wraps, with a call to
> > + hardened_atomic_overflow().
> > +
> > +config HARDENED_ATOMIC
> > + bool "Prevent reference counter overflow in atomic_t"
> > + depends on HAVE_ARCH_HARDENED_ATOMIC
> > + select BUG
> > + help
> > + This option catches counter wrapping in atomic_t, which
> > + can turn refcounting overflow bugs into resource
> > + consumption bugs instead of exploitable use-after-free
> > + flaws. This feature has a negligible
> > + performance impact and therefore recommended to be turned
> > + on for security reasons.
> > +
> > source security/selinux/Kconfig
> > source security/smack/Kconfig
> > source security/tomoyo/Kconfig
> > --
> > 2.7.4
> >
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