Messages in this thread |  | | Date | Wed, 28 Sep 2022 18:27:36 +0200 | Subject | Re: [PATCH v2 01/16] slab: Remove __malloc attribute from realloc functions | From | Vlastimil Babka <> |
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On 9/28/22 09:26, Geert Uytterhoeven wrote: > Hi Kees, > > On Fri, Sep 23, 2022 at 10:35 PM Kees Cook <keescook@chromium.org> wrote: >> 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 <cl@linux.com> >> Cc: Pekka Enberg <penberg@kernel.org> >> Cc: David Rientjes <rientjes@google.com> >> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> >> Cc: Andrew Morton <akpm@linux-foundation.org> >> Cc: Vlastimil Babka <vbabka@suse.cz> >> Cc: Roman Gushchin <roman.gushchin@linux.dev> >> Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com> >> Cc: Marco Elver <elver@google.com> >> Cc: linux-mm@kvack.org >> Signed-off-by: Kees Cook <keescook@chromium.org> > > 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.
So IIUC it was wrong to remove the #ifdefs?
> [1] http://kisskb.ellerman.id.au/kisskb/buildresult/14803908/ > [2] http://kisskb.ellerman.id.au/kisskb/head/1bd8b75fe6adeaa89d02968bdd811ffe708cf839/ > > > >> --- >> include/linux/compiler_types.h | 13 +++++-------- >> include/linux/slab.h | 12 ++++++------ >> mm/slab_common.c | 4 ++-- >> 3 files changed, 13 insertions(+), 16 deletions(-) >> >> diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h >> index 4f2a819fd60a..f141a6f6b9f6 100644 >> --- a/include/linux/compiler_types.h >> +++ b/include/linux/compiler_types.h >> @@ -271,15 +271,12 @@ struct ftrace_likely_data { >> >> /* >> * Any place that could be marked with the "alloc_size" attribute is also >> - * a place to be marked with the "malloc" attribute. Do this as part of the >> - * __alloc_size macro to avoid redundant attributes and to avoid missing a >> - * __malloc marking. >> + * a place to be marked with the "malloc" attribute, except those that may >> + * be performing a _reallocation_, as that may alias the existing pointer. >> + * For these, use __realloc_size(). >> */ >> -#ifdef __alloc_size__ >> -# define __alloc_size(x, ...) __alloc_size__(x, ## __VA_ARGS__) __malloc >> -#else >> -# define __alloc_size(x, ...) __malloc >> -#endif >> +#define __alloc_size(x, ...) __alloc_size__(x, ## __VA_ARGS__) __malloc >> +#define __realloc_size(x, ...) __alloc_size__(x, ## __VA_ARGS__) >> >> #ifndef asm_volatile_goto >> #define asm_volatile_goto(x...) asm goto(x) >> diff --git a/include/linux/slab.h b/include/linux/slab.h >> index 0fefdf528e0d..41bd036e7551 100644 >> --- a/include/linux/slab.h >> +++ b/include/linux/slab.h >> @@ -184,7 +184,7 @@ int kmem_cache_shrink(struct kmem_cache *s); >> /* >> * Common kmalloc functions provided by all allocators >> */ >> -void * __must_check krealloc(const void *objp, size_t new_size, gfp_t flags) __alloc_size(2); >> +void * __must_check krealloc(const void *objp, size_t new_size, gfp_t flags) __realloc_size(2); >> void kfree(const void *objp); >> void kfree_sensitive(const void *objp); >> size_t __ksize(const void *objp); >> @@ -647,10 +647,10 @@ static inline __alloc_size(1, 2) void *kmalloc_array(size_t n, size_t size, gfp_ >> * @new_size: new size of a single member of the array >> * @flags: the type of memory to allocate (see kmalloc) >> */ >> -static inline __alloc_size(2, 3) void * __must_check krealloc_array(void *p, >> - size_t new_n, >> - size_t new_size, >> - gfp_t flags) >> +static inline __realloc_size(2, 3) void * __must_check krealloc_array(void *p, >> + size_t new_n, >> + size_t new_size, >> + gfp_t flags) >> { >> size_t bytes; >> >> @@ -774,7 +774,7 @@ static inline __alloc_size(1, 2) void *kvcalloc(size_t n, size_t size, gfp_t fla >> } >> >> extern void *kvrealloc(const void *p, size_t oldsize, size_t newsize, gfp_t flags) >> - __alloc_size(3); >> + __realloc_size(3); >> extern void kvfree(const void *addr); >> extern void kvfree_sensitive(const void *addr, size_t len); >> >> diff --git a/mm/slab_common.c b/mm/slab_common.c >> index 17996649cfe3..457671ace7eb 100644 >> --- a/mm/slab_common.c >> +++ b/mm/slab_common.c >> @@ -1134,8 +1134,8 @@ module_init(slab_proc_init); >> >> #endif /* CONFIG_SLAB || CONFIG_SLUB_DEBUG */ >> >> -static __always_inline void *__do_krealloc(const void *p, size_t new_size, >> - gfp_t flags) >> +static __always_inline __realloc_size(2) void * >> +__do_krealloc(const void *p, size_t new_size, gfp_t flags) >> { >> void *ret; >> size_t ks; >> -- >> 2.34.1 >> > > > -- > 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
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