slab: fix a crash by reading /proc/slab_allocators

Qian Cai · torvalds · commit fcf88917dd43 · 2019-04-07T19:23:12.000-10:00
The commit 510ded3 ("slab: implement slab_root_caches list") changes the name of the list node within "struct kmem_cache" from "list" to "root_caches_node", but leaks_show() still use the "list" which causes a crash when reading /proc/slab_allocators. You need to have CONFIG_SLAB=y and CONFIG_MEMCG=y to see the problem, because without MEMCG all slab caches are root caches, and the "list" node happens to be the right one. Fixes: 510ded3 ("slab: implement slab_root_caches list") Signed-off-by: Qian Cai <cai@lca.pw> Reviewed-by: Tobin C. Harding <tobin@kernel.org> Cc: Tejun Heo <tj@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/slab.c b/mm/slab.c
@@ -4308,7 +4308,8 @@ static void show_symbol(struct seq_file *m, unsigned long address)
 
 static int leaks_show(struct seq_file *m, void *p)
 {
-	struct kmem_cache *cachep = list_entry(p, struct kmem_cache, list);
+	struct kmem_cache *cachep = list_entry(p, struct kmem_cache,
+					       root_caches_node);
 	struct page *page;
 	struct kmem_cache_node *n;
 	const char *name;

Original file line number	Diff line number	Diff line change
`@@ -4308,7 +4308,8 @@ static void show_symbol(struct seq_file *m, unsigned long address)`
`4308`	`4308`
`4309`	`4309`	`static int leaks_show(struct seq_file m, void p)`
`4310`	`4310`	`{`
`4311`		`- struct kmem_cache *cachep = list_entry(p, struct kmem_cache, list);`
	`4311`	`+ struct kmem_cache *cachep = list_entry(p, struct kmem_cache,`
	`4312`	`+ root_caches_node);`
`4312`	`4313`	`struct page *page;`
`4313`	`4314`	`struct kmem_cache_node *n;`
`4314`	`4315`	`const char *name;`