linux-kernel - [PATCH] slub: avoid potential NULL dereference or corruption

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 22 Nov 2011 15:53:49 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Christoph Lameter <cl@...ux-foundation.org>
Cc:	Pekka Enberg <penberg@...nel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: [PATCH] slub: avoid potential NULL dereference or corruption

show_slab_objects() can trigger NULL dereferences or memory corruption.

Another cpu can change its c->page to NULL or c->node to NUMA_NO_NODE
while we use them.

Use ACCESS_ONCE(c->page) and ACCESS_ONCE(c->node) to make sure this
cannot happen.

Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
---
 mm/slub.c |   22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 7d2a996..e8e6714 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4436,29 +4436,33 @@ static ssize_t show_slab_objects(struct kmem_cache *s,
 		for_each_possible_cpu(cpu) {
 			struct kmem_cache_cpu *c = per_cpu_ptr(s->cpu_slab, cpu);
 			struct page *page;
+			int node;
 
-			if (!c || c->node < 0)
+			if (!c)
 				continue;
-
-			if (c->page) {
-					if (flags & SO_TOTAL)
-						x = c->page->objects;
+			node = ACCESS_ONCE(c->node);
+			if (node < 0)
+				continue;
+			page = ACCESS_ONCE(c->page);
+			if (page) {
+				if (flags & SO_TOTAL)
+					x = page->objects;
 				else if (flags & SO_OBJECTS)
-					x = c->page->inuse;
+					x = page->inuse;
 				else
 					x = 1;
 
 				total += x;
-				nodes[c->node] += x;
+				nodes[node] += x;
 			}
 			page = c->partial;
 
 			if (page) {
 				x = page->pobjects;
                                 total += x;
-                                nodes[c->node] += x;
+                                nodes[node] += x;
 			}
-			per_cpu[c->node]++;
+			per_cpu[node]++;
 		}
 	}
 


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/