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SubjectRe: [RFC PATCH v1 40/50] arch/*/include/asm/stackprotector.h: Use get_random_canary() consistently
On Tue, Dec 10, 2019 at 12:35:14AM -0500, George Spelvin wrote:
> ... in boot_init_stack_canary().
>
> This is the archetypical example of where the extra security of
> get_random_bytes() is wasted. The canary is only important as
> long as it's stored in __stack_chk_guard.
>
> It's also a great example of code that has been copied around
> a lot and not updated.
>
> Remove the XOR with LINUX_VERSION_CODE as it's pointless; the inclusion
> of utsname() in init_std_data in the random seeding obviates it.
>
> The XOR with the TSC on x86 and mtfb() on powerPC were left in,
> as I haven't proved them redundant yet. For those, we call
> get_random_long(), xor, and mask manually.
>
> FUNCTIONAL CHANGE: mips and xtensa were changed from 64-bit
> get_random_long() to 56-bit get_random_canary() to match the
> others, in accordance with the logic in CANARY_MASK.
>
> (We could do 1 bit better and zero *one* of the two high bytes.)
>
> Signed-off-by: George Spelvin <lkml@sdf.org>
> Cc: Russell King <linux@armlinux.org.uk>
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Ralf Baechle <ralf@linux-mips.org>
> Cc: Paul Burton <paulburton@kernel.org>
> Cc: James Hogan <jhogan@kernel.org>
> Cc: linux-mips@vger.kernel.org
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: linuxppc-dev@lists.ozlabs.org
> Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
> Cc: Rich Felker <dalias@libc.org>
> Cc: linux-sh@vger.kernel.org
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: x86@kernel.org
> Cc: Chris Zankel <chris@zankel.net>
> Cc: Max Filippov <jcmvbkbc@gmail.com>
> Cc: linux-xtensa@linux-xtensa.org
> ---
> arch/arm/include/asm/stackprotector.h | 9 +++------
> arch/arm64/include/asm/stackprotector.h | 8 ++------
> arch/mips/include/asm/stackprotector.h | 7 ++-----
> arch/powerpc/include/asm/stackprotector.h | 6 ++----
> arch/sh/include/asm/stackprotector.h | 8 ++------
> arch/x86/include/asm/stackprotector.h | 4 ++--
> arch/xtensa/include/asm/stackprotector.h | 7 ++-----
> 7 files changed, 15 insertions(+), 34 deletions(-)

Just found this kicking around in the depths of my inbox. Is the series
dead?

Will

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