mm/slub: only zero requested size of buffer for kzalloc when debug enabled

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kzalloc/kmalloc will round up the request size to a fixed size
(mostly power of 2), so the allocated memory could be more than
requested. Currently kzalloc family APIs will zero all the
allocated memory.

To detect out-of-bound usage of the extra allocated memory, only
zero the requested part, so that redzone sanity check could be
added to the extra space later.

For kzalloc users who will call ksize() later and utilize this
extra space, please be aware that the space is not zeroed any
more when debug is enabled. (Thanks to Kees Cook's effort to
sanitize all ksize() user cases [1], this won't be a big issue).

[1]. https://lore.kernel.org/all/20220922031013.2150682-1-keescook@chromium.org/#r

Signed-off-by: Feng Tang <feng.tang@intel.com>
Acked-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

...

This commit is contained in:

Feng Tang 2022-10-21 11:24:03 +08:00 • committed by Vlastimil Babka

parent c18c20f162

commit 9ce67395f5

3 changed files with 27 additions and 8 deletions

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7

mm/slab.c

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18

mm/slab.h

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10

mm/slub.c

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