slab: Avoid race on slab->obj_exts in alloc_slab_obj_exts

If two competing threads enter alloc_slab_obj_exts() and one of them
fails to allocate the object extension vector, it might override the
valid slab->obj_exts allocated by the other thread with
OBJEXTS_ALLOC_FAIL. This will cause the thread that lost this race and
expects a valid pointer to dereference a NULL pointer later on.

Update slab->obj_exts atomically using cmpxchg() to avoid
slab->obj_exts overrides by racing threads.

Thanks for Vlastimil and Suren's help with debugging.

Fixes: f7381b911640 ("slab: mark slab->obj_exts allocation failures unconditionally")
Cc: <[email protected]>
Suggested-by: Suren Baghdasaryan <[email protected]>
Signed-off-by: Hao Ge <[email protected]>
Reviewed-by: Harry Yoo <[email protected]>
Reviewed-by: Suren Baghdasaryan <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Vlastimil Babka <[email protected]>

0 files changed, 0 insertions, 0 deletions