Commit 52f23478081ae0 ("mm/slub.c: fix corrupted freechain in deactivate_slab()") suffered an update when picked up from LKML [1].

Specifically, relocating 'freelist = NULL' into 'freelist_corrupted()' created a no-op statement. Fix it by sticking to the behavior intended in the original patch [1]. In addition, make freelist_corrupted() immune to passing NULL instead of &freelist.

The issue has been spotted via static analysis and code review.

[1] https://lore.kernel.org/linux-mm/20200331031450.12182-1-dongli.zhang@oracle....

Fixes: 52f23478081ae0 ("mm/slub.c: fix corrupted freechain in deactivate_slab()") Cc: Andrew Morton akpm@linux-foundation.org Cc: Dongli Zhang dongli.zhang@oracle.com Cc: stable@vger.kernel.org Signed-off-by: Eugeniu Rosca erosca@de.adit-jv.com ---

v2: - Address the review finding from Dongli Zhang in: https://lore.kernel.org/linux-mm/f93a9f06-8608-6f28-27c0-b17f86dca55b@oracle...

-------8<------- This is good to me. However, this would confuse people when CONFIG_SLUB_DEBUG is not defined. While reading the source code, people may be curious why to reset freelist when CONFIG_SLUB_DEBUG is even not defined. -------8<-------

v1: - https://lore.kernel.org/linux-mm/20200811124656.10308-1-erosca@de.adit-jv.co...

mm/slub.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c index 68c02b2eecd9..d4177aecedf6 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -672,12 +672,12 @@ static void slab_fix(struct kmem_cache *s, char *fmt, ...) }

static bool freelist_corrupted(struct kmem_cache *s, struct page *page, - void *freelist, void *nextfree) + void **freelist, void *nextfree) { if ((s->flags & SLAB_CONSISTENCY_CHECKS) && - !check_valid_pointer(s, page, nextfree)) { - object_err(s, page, freelist, "Freechain corrupt"); - freelist = NULL; + !check_valid_pointer(s, page, nextfree) && freelist) { + object_err(s, page, *freelist, "Freechain corrupt"); + *freelist = NULL; slab_fix(s, "Isolate corrupted freechain"); return true; } @@ -1494,7 +1494,7 @@ static inline void dec_slabs_node(struct kmem_cache *s, int node, int objects) {}

static bool freelist_corrupted(struct kmem_cache *s, struct page *page, - void *freelist, void *nextfree) + void **freelist, void *nextfree) { return false; } @@ -2184,7 +2184,7 @@ static void deactivate_slab(struct kmem_cache *s, struct page *page, * 'freelist' is already corrupted. So isolate all objects * starting at 'freelist'. */ - if (freelist_corrupted(s, page, freelist, nextfree)) + if (freelist_corrupted(s, page, &freelist, nextfree)) break;

do {