On Tue, 11 Aug 2020 14:46:56 +0200 Eugeniu Rosca <erosca@xxxxxxxxxxxxxx> wrote:
> 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]. Prefer the lowest-line-count solution.
>
> [1] https://lore.kernel.org/linux-mm/20200331031450.12182-1-dongli.zhang@xxxxxxxxxx/
>
> ...
>
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -677,7 +677,6 @@ static bool freelist_corrupted(struct kmem_cache *s, struct page *page,
> if ((s->flags & SLAB_CONSISTENCY_CHECKS) &&
> !check_valid_pointer(s, page, nextfree)) {
> object_err(s, page, freelist, "Freechain corrupt");
> - freelist = NULL;
> slab_fix(s, "Isolate corrupted freechain");
> return true;
> }
> @@ -2184,8 +2183,10 @@ 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)) {
> + freelist = NULL;
> break;
> + }
>
> do {
> prior = page->freelist;
Looks right.
What are the runtime effects of this change? In other words, what are
the end user visible effects of the present defect?
