On 9/28/22 19:13, Kees Cook wrote:
On Wed, Sep 28, 2022 at 09:26:15AM +0200, Geert Uytterhoeven wrote:
Hi Kees,
On Fri, Sep 23, 2022 at 10:35 PM Kees Cook <keescook@xxxxxxxxxxxx> 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@xxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Roman Gushchin <roman.gushchin@xxxxxxxxx>
Cc: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx>
Cc: Marco Elver <elver@xxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Thanks for your patch, which is now commit 63caa04ec60583b1 ("slab:
Remove __malloc attribute from realloc functions") in next-20220927.
Noreply@xxxxxxxxxxxxxx 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.
Even in latest next I can see at the end of include/linux/compiler-gcc.h
/*
* Prior to 9.1, -Wno-alloc-size-larger-than (and therefore the "alloc_size"
* attribute) do not work, and must be disabled.
*/
#if GCC_VERSION < 90100
#undef __alloc_size__
#endif
-Kees
