Re: [PATCH v2 01/16] slab: Remove __malloc attribute from realloc functions
From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: 2022-09-29 09:00:57
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Hi Michael, On Thu, Sep 29, 2022 at 10:36 AM Michael Ellerman [off-list ref] wrote:
Kees Cook [off-list ref] writes:quoted
On Wed, Sep 28, 2022 at 09:26:15AM +0200, Geert Uytterhoeven wrote:quoted
On Fri, Sep 23, 2022 at 10:35 PM Kees Cook [off-list ref] wrote:quoted
The __malloc attribute should not be applied to "realloc" functions, as the returned pointer may alias the storage of the prior pointer. Instead of splitting __malloc from __alloc_size, which would be a huge amount of churn, just create __realloc_size for the few cases where it is needed. Additionally removes the conditional test for __alloc_size__, which is always defined now. Cc: Christoph Lameter <redacted> Cc: Pekka Enberg <penberg@kernel.org> Cc: David Rientjes <rientjes@google.com> Cc: Joonsoo Kim <redacted> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Vlastimil Babka <redacted> Cc: Roman Gushchin <roman.gushchin@linux.dev> Cc: Hyeonggon Yoo <redacted> Cc: Marco Elver <elver@google.com> Cc: linux-mm@kvack.org Signed-off-by: Kees Cook <redacted>Thanks for your patch, which is now commit 63caa04ec60583b1 ("slab: Remove __malloc attribute from realloc functions") in next-20220927. Noreply@ellerman.id.au reported all gcc8-based builds to fail (e.g. [1], more at [2]): In file included from <command-line>: ./include/linux/percpu.h: In function ‘__alloc_reserved_percpu’: ././include/linux/compiler_types.h:279:30: error: expected declaration specifiers before ‘__alloc_size__’ #define __alloc_size(x, ...) __alloc_size__(x, ## __VA_ARGS__) __malloc ^~~~~~~~~~~~~~ ./include/linux/percpu.h:120:74: note: in expansion of macro ‘__alloc_size’ [...] It's building fine with e.g. gcc-9 (which is my usual m68k cross-compiler). Reverting this commit on next-20220927 fixes the issue. [1] http://kisskb.ellerman.id.au/kisskb/buildresult/14803908/ [2] http://kisskb.ellerman.id.au/kisskb/head/1bd8b75fe6adeaa89d02968bdd811ffe708cf839/Eek! Thanks for letting me know. I'm confused about this -- __alloc_size__ wasn't optional in compiler_attributes.h -- but obviously I broke something! I'll go figure this out.This fixes it for me.
Kees submitted a similar patch 20 minutes before: https://lore.kernel.org/all/20220929081642.1932200-1-keescook@chromium.org (local)
quoted hunk ↗ jump to hunk
--- a/include/linux/compiler_types.h +++ b/include/linux/compiler_types.h@@ -275,8 +275,13 @@ struct ftrace_likely_data { * be performing a _reallocation_, as that may alias the existing pointer. * For these, use __realloc_size(). */ -#define __alloc_size(x, ...) __alloc_size__(x, ## __VA_ARGS__) __malloc -#define __realloc_size(x, ...) __alloc_size__(x, ## __VA_ARGS__) +#ifdef __alloc_size__ +# define __alloc_size(x, ...) __alloc_size__(x, ## __VA_ARGS__) __malloc +# define __realloc_size(x, ...) __alloc_size__(x, ## __VA_ARGS__) +#else +# define __alloc_size(x, ...) __malloc +# define __realloc_size(x, ...) +#endif #ifndef asm_volatile_goto #define asm_volatile_goto(x...) asm goto(x)
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds