mm: slub: fix conversion of freelist_corrupted()

Commit b8c426bb8e84f1 ("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.com/

Fixes: b8c426bb8e84f1 ("mm/slub.c: fix corrupted freechain in deactivate_slab()")
Signed-off-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Dongli Zhang <dongli.zhang@oracle.com>
Cc: Joe Jin <joe.jin@oracle.com>
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: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20200824130643.10291-1-erosca@de.adit-jv.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/slub.c b/mm/slub.c
index 68c02b2eecd90334588493cd0b28058c15c4c11d..d4177aecedf6bb7cfd45b74b61b8ce2243eebc68 100644 (file)
--- 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 {