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Message-Id: <1486164412-7338-5-git-send-email-keescook@chromium.org>
Date: Fri, 3 Feb 2017 15:26:52 -0800
From: Kees Cook <keescook@...omium.org>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Kees Cook <keescook@...omium.org>,
elena.reshetova@...el.com,
gregkh@...uxfoundation.org,
arnd@...db.de,
tglx@...utronix.de,
mingo@...nel.org,
h.peter.anvin@...el.com,
will.deacon@....com,
dwindsor@...il.com,
Hans Liljestrand <ishkamiel@...il.com>,
dhowells@...hat.com,
linux-kernel@...r.kernel.org,
kernel-hardening@...ts.openwall.com
Subject: [PATCH 4/4] refcount: Report failures through CHECK_DATA_CORRUPTION
This converts from WARN_ON() to CHECK_DATA_CORRUPTION() in the
CONFIG_DEBUG_REFCOUNT case. Additionally moves refcount_t sanity check
conditionals into regular function flow. Since CHECK_DATA_CORRUPTION()
is marked __much_check, we override few cases where the failure has
already been handled but we want to explicitly report it.
Signed-off-by: Kees Cook <keescook@...omium.org>
---
include/linux/refcount.h | 35 ++++++++++++++++++++++-------------
lib/Kconfig.debug | 2 ++
2 files changed, 24 insertions(+), 13 deletions(-)
diff --git a/include/linux/refcount.h b/include/linux/refcount.h
index 5b89cad62237..ef32910c7dd8 100644
--- a/include/linux/refcount.h
+++ b/include/linux/refcount.h
@@ -43,10 +43,10 @@
#include <linux/spinlock.h>
#if CONFIG_DEBUG_REFCOUNT
-#define REFCOUNT_WARN(cond, str) WARN_ON(cond)
+#define REFCOUNT_CHECK(cond, str) CHECK_DATA_CORRUPTION(cond, str)
#define __refcount_check __must_check
#else
-#define REFCOUNT_WARN(cond, str) (void)(cond)
+#define REFCOUNT_CHECK(cond, str) (!!(cond))
#define __refcount_check
#endif
@@ -86,14 +86,18 @@ bool refcount_add_not_zero(unsigned int i, refcount_t *r)
break;
}
- REFCOUNT_WARN(new == UINT_MAX, "refcount_t: saturated; leaking memory.\n");
+ val = REFCOUNT_CHECK(new == UINT_MAX,
+ "refcount_t: add saturated; leaking memory.\n");
return true;
}
static inline void refcount_add(unsigned int i, refcount_t *r)
{
- REFCOUNT_WARN(!refcount_add_not_zero(i, r), "refcount_t: addition on 0; use-after-free.\n");
+ bool __always_unused b;
+
+ b = REFCOUNT_CHECK(!refcount_add_not_zero(i, r),
+ "refcount_t: addition on 0; use-after-free.\n");
}
/*
@@ -121,7 +125,8 @@ bool refcount_inc_not_zero(refcount_t *r)
break;
}
- REFCOUNT_WARN(new == UINT_MAX, "refcount_t: saturated; leaking memory.\n");
+ val = REFCOUNT_CHECK(new == UINT_MAX,
+ "refcount_t: inc saturated; leaking memory.\n");
return true;
}
@@ -134,7 +139,10 @@ bool refcount_inc_not_zero(refcount_t *r)
*/
static inline void refcount_inc(refcount_t *r)
{
- REFCOUNT_WARN(!refcount_inc_not_zero(r), "refcount_t: increment on 0; use-after-free.\n");
+ bool __always_unused b;
+
+ b = REFCOUNT_CHECK(!refcount_inc_not_zero(r),
+ "refcount_t: increment on 0; use-after-free.\n");
}
/*
@@ -155,10 +163,9 @@ bool refcount_sub_and_test(unsigned int i, refcount_t *r)
return false;
new = val - i;
- if (new > val) {
- REFCOUNT_WARN(new > val, "refcount_t: underflow; use-after-free.\n");
+ if (REFCOUNT_CHECK(new > val,
+ "refcount_t: sub underflow; use-after-free.\n"))
return false;
- }
if (atomic_try_cmpxchg_release(&r->refs, &val, new))
break;
@@ -183,7 +190,10 @@ bool refcount_dec_and_test(refcount_t *r)
static inline
void refcount_dec(refcount_t *r)
{
- REFCOUNT_WARN(refcount_dec_and_test(r), "refcount_t: decrement hit 0; leaking memory.\n");
+ bool __always_unused b;
+
+ b = REFCOUNT_CHECK(refcount_dec_and_test(r),
+ "refcount_t: decrement hit 0; leaking memory.\n");
}
/*
@@ -224,10 +234,9 @@ bool refcount_dec_not_one(refcount_t *r)
return false;
new = val - 1;
- if (new > val) {
- REFCOUNT_WARN(new > val, "refcount_t: underflow; use-after-free.\n");
+ if (REFCOUNT_CHECK(new > val,
+ "refcount_t: dec underflow; use-after-free.\n"))
return true;
- }
if (atomic_try_cmpxchg_release(&r->refs, &val, new))
break;
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 20fde8d4523a..01e7aa578456 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -731,6 +731,7 @@ source "lib/Kconfig.kasan"
config DEBUG_REFCOUNT
bool "Verbose refcount checks"
+ depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION
help
Say Y here if you want reference counters (refcount_t and kref) to
generate WARNs on dubious usage. Without this refcount_t will still
@@ -2011,6 +2012,7 @@ config TEST_STATIC_KEYS
config BUG_ON_DATA_CORRUPTION
bool "Trigger a BUG when data corruption is detected"
select DEBUG_LIST
+ select DEBUG_REFCOUNT
help
Select this option if the kernel should BUG when it encounters
data corruption in kernel memory structures when they get checked
--
2.7.4
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