queue-next/mm-slub-fix-conversion-of-freelist_corrupted.patch

From 0da021477ea2a817accd1650b9efede52f0c8efb Mon Sep 17 00:00:00 2001
From: Eugeniu Rosca <erosca@de.adit-jv.com>
Date: Thu, 20 Aug 2020 10:01:23 +1000
Subject: [PATCH] mm: slub: fix conversion of freelist_corrupted()

commit 0da021477ea2a817accd1650b9efede52f0c8efb upstream.

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.

The issue popped up as a result of static analysis and code review.
Therefore, I lack any specific runtime behavior example being fixed.

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

Link: http://lkml.kernel.org/r/20200811124656.10308-1-erosca@de.adit-jv.com
Fixes: 52f23478081ae0 ("mm/slub.c: fix corrupted freechain in deactivate_slab()")
Signed-off-by: Eugeniu Rosca <erosca@de.adit-jv.com>
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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>

diff --git a/mm/slub.c b/mm/slub.c
index 68c02b2eecd9..9a3e963b02a3 100644
--- 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;
-- 
2.27.0