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Message-ID: <20160915151045.GD9316@leverpostej>
Date: Thu, 15 Sep 2016 16:10:45 +0100
From: Mark Rutland <mark.rutland@....com>
To: Catalin Marinas <catalin.marinas@....com>
Cc: linux-arm-kernel@...ts.infradead.org, Will Deacon <will.deacon@....com>,
James Morse <james.morse@....com>,
Kees Cook <keescook@...omium.org>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>,
AKASHI Takahiro <takahiro.akashi@...aro.org>,
kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH v3 1/7] arm64: Factor out PAN enabling/disabling into
separate uaccess_* macros
Hi Catalin,
On Tue, Sep 13, 2016 at 06:46:31PM +0100, Catalin Marinas wrote:
> This patch moves the directly coded alternatives for turning PAN on/off
> into separate uaccess_{enable,disable} macros or functions. The asm
> macros take a few arguments which will be used in subsequent patches.
>
> Note that any (unlikely) access that the compiler might generate between
> uaccess_enable() and uaccess_disable(), other than those explicitly
> specified by the user access code, will not be protected by PAN.
There's one missing include that I've noted below, along with a number
we can now drop. Otherwise, the important parts all look good to me.
With the includes fixed up:
Reviewed-by: Mark Rutland <mark.rutland@....com>
[...]
> Cc: Will Deacon <will.deacon@....com>
> Cc: James Morse <james.morse@....com>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Mark Rutland <mark.rutland@....com>
> Signed-off-by: Catalin Marinas <catalin.marinas@....com>
> ---
> arch/arm64/include/asm/futex.h | 14 +++----
> arch/arm64/include/asm/uaccess.h | 79 ++++++++++++++++++++++++++++++++----
> arch/arm64/kernel/armv8_deprecated.c | 10 ++---
> arch/arm64/lib/clear_user.S | 8 ++--
> arch/arm64/lib/copy_from_user.S | 8 ++--
> arch/arm64/lib/copy_in_user.S | 8 ++--
> arch/arm64/lib/copy_to_user.S | 8 ++--
> 7 files changed, 95 insertions(+), 40 deletions(-)
>
> diff --git a/arch/arm64/include/asm/futex.h b/arch/arm64/include/asm/futex.h
> index f2585cdd32c2..71dfa3b42313 100644
> --- a/arch/arm64/include/asm/futex.h
> +++ b/arch/arm64/include/asm/futex.h
> @@ -27,9 +27,9 @@
> #include <asm/sysreg.h>
>
> #define __futex_atomic_op(insn, ret, oldval, uaddr, tmp, oparg) \
> +do { \
> + uaccess_enable(); \
> asm volatile( \
> - ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN, \
> - CONFIG_ARM64_PAN) \
> " prfm pstl1strm, %2\n" \
> "1: ldxr %w1, %2\n" \
> insn "\n" \
> @@ -44,11 +44,11 @@
> " .popsection\n" \
> _ASM_EXTABLE(1b, 4b) \
> _ASM_EXTABLE(2b, 4b) \
> - ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN, \
> - CONFIG_ARM64_PAN) \
> : "=&r" (ret), "=&r" (oldval), "+Q" (*uaddr), "=&r" (tmp) \
> : "r" (oparg), "Ir" (-EFAULT) \
> - : "memory")
> + : "memory"); \
> + uaccess_disable(); \
> +} while (0)
With the uaccess_{enable,disable}* macros, we can drop the includes for
<asm/alternative.h>, <asm/cpufeature.h>, and <asm/sysreg.h> from
futex.h, as we no longer (directly) use anything from those.
[...]
> diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
> index c47257c91b77..cc6c32d4dcc4 100644
> --- a/arch/arm64/include/asm/uaccess.h
> +++ b/arch/arm64/include/asm/uaccess.h
> @@ -321,4 +357,31 @@ extern long strncpy_from_user(char *dest, const char __user *src, long count);
> extern __must_check long strlen_user(const char __user *str);
> extern __must_check long strnlen_user(const char __user *str, long n);
>
> +#else /* __ASSEMBLY__ */
> +
> +#include <asm/alternative.h>
> +#include <asm/assembler.h>
We also need <asm/sysreg.h> for SET_PSTATE_PAN()
Given we use that and <asm/alternative.h> either way, should we pull
those above the #ifdef __ASSEMBLY__? I have no feeling either way.
[...]
> diff --git a/arch/arm64/kernel/armv8_deprecated.c b/arch/arm64/kernel/armv8_deprecated.c
> index 42ffdb54e162..7156e7bfcd89 100644
> --- a/arch/arm64/kernel/armv8_deprecated.c
> +++ b/arch/arm64/kernel/armv8_deprecated.c
> @@ -281,9 +281,9 @@ static void __init register_insn_emulation_sysctl(struct ctl_table *table)
> * Error-checking SWP macros implemented using ldxr{b}/stxr{b}
> */
> #define __user_swpX_asm(data, addr, res, temp, B) \
> +do { \
> + uaccess_enable(); \
> __asm__ __volatile__( \
> - ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN, \
> - CONFIG_ARM64_PAN) \
> "0: ldxr"B" %w2, [%3]\n" \
> "1: stxr"B" %w0, %w1, [%3]\n" \
> " cbz %w0, 2f\n" \
> @@ -299,11 +299,11 @@ static void __init register_insn_emulation_sysctl(struct ctl_table *table)
> " .popsection" \
> _ASM_EXTABLE(0b, 4b) \
> _ASM_EXTABLE(1b, 4b) \
> - ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN, \
> - CONFIG_ARM64_PAN) \
> : "=&r" (res), "+r" (data), "=&r" (temp) \
> : "r" (addr), "i" (-EAGAIN), "i" (-EFAULT) \
> - : "memory")
> + : "memory"); \
> + uaccess_disable(); \
> +} while (0)
With this, we can drop the include of <asm/alternative.h>, though unlike
futex.h we need to keep <asm/cpufeature.h> and <asm/sysreg.h>.
[...]
> diff --git a/arch/arm64/lib/clear_user.S b/arch/arm64/lib/clear_user.S
> index 5d1cad3ce6d6..08b5f18ba604 100644
> --- a/arch/arm64/lib/clear_user.S
> +++ b/arch/arm64/lib/clear_user.S
> @@ -17,10 +17,10 @@
> */
> #include <linux/linkage.h>
>
> -#include <asm/alternative.h>
> #include <asm/assembler.h>
> #include <asm/cpufeature.h>
> #include <asm/sysreg.h>
> +#include <asm/uaccess.h>
As with futex.h, we can drop <asm/assembler.h>, <asm/cpufeature.h>, and
<asm/sysreg.h>, as the uaccess_{enable,disable}* macros mean we no
longer use anything from those directly.
[...]
> diff --git a/arch/arm64/lib/copy_from_user.S b/arch/arm64/lib/copy_from_user.S
> index 0b90497d4424..6505ec81f1da 100644
> --- a/arch/arm64/lib/copy_from_user.S
> +++ b/arch/arm64/lib/copy_from_user.S
> @@ -16,11 +16,11 @@
>
> #include <linux/linkage.h>
>
> -#include <asm/alternative.h>
> #include <asm/assembler.h>
> #include <asm/cache.h>
> #include <asm/cpufeature.h>
> #include <asm/sysreg.h>
> +#include <asm/uaccess.h>
Likewise, we can also drop <asm/assembler.h>, <asm/cpufeature.h>, and
<asm/sysreg.h> here.
[...]
> diff --git a/arch/arm64/lib/copy_in_user.S b/arch/arm64/lib/copy_in_user.S
> index f7292dd08c84..9b04ff3ab610 100644
> --- a/arch/arm64/lib/copy_in_user.S
> +++ b/arch/arm64/lib/copy_in_user.S
> @@ -18,11 +18,11 @@
>
> #include <linux/linkage.h>
>
> -#include <asm/alternative.h>
> #include <asm/assembler.h>
> #include <asm/cache.h>
> #include <asm/cpufeature.h>
> #include <asm/sysreg.h>
> +#include <asm/uaccess.h>
Likewise, we can also drop <asm/assembler.h>, <asm/cpufeature.h>, and
<asm/sysreg.h> here.
[...]
> diff --git a/arch/arm64/lib/copy_to_user.S b/arch/arm64/lib/copy_to_user.S
> index 7a7efe255034..8077e4f34d56 100644
> --- a/arch/arm64/lib/copy_to_user.S
> +++ b/arch/arm64/lib/copy_to_user.S
> @@ -16,11 +16,11 @@
>
> #include <linux/linkage.h>
>
> -#include <asm/alternative.h>
> #include <asm/assembler.h>
> #include <asm/cache.h>
> #include <asm/cpufeature.h>
> #include <asm/sysreg.h>
> +#include <asm/uaccess.h>
Likewise, we can also drop <asm/assembler.h>, <asm/cpufeature.h>, and
<asm/sysreg.h> here.
Thanks,
Mark.
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