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@xxxxxxxxxx/
Fixes: 52f23478081ae0 ("mm/slub.c: fix corrupted freechain in deactivate_slab()")
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Dongli Zhang <dongli.zhang@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Eugeniu Rosca <erosca@xxxxxxxxxxxxxx>
---
v2:
- Address the review finding from Dongli Zhang in:
https://lore.kernel.org/linux-mm/f93a9f06-8608-6f28-27c0-b17f86dca55b@xxxxxxxxxx/
-------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@xxxxxxxxxxxxxx/
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 {
--
2.28.0
