[PATCH v2 1/2] SLUB: Fix merged slab cache names

Pekka Enberg
2010-09-14T18:48:27Z

As explained by Linus "I'm Proud to be an American" Torvalds:

Looking at the merging code, I actually think it's totally
buggy. If you have something like this:

- load module A: create slab cache A

- load module B: create slab cache B that can merge with A

- unload module A

- "cat /proc/slabinfo": BOOM. Oops.

exactly because the name is not handled correctly, and you'll have
module B holding open a slab cache that has a name pointer that points
to module A that no longer exists.

This patch fixes the problem by using kstrdup() to allocate dynamic memory for
->name of "struct kmem_cache" as suggested by Christoph Lameter.

Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Pekka Enberg <penberg@kernel.org>
---
mm/slub.c | 24 +++++++++++++++++++++++-
1 files changed, 23 insertions(+), 1 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 13fffe1..a31c033 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -210,6 +210,7 @@ static inline int sysfs_slab_alias(struct kmem_cache *s, const char *p)
{ return 0; }
static inline void sysfs_slab_remove(struct kmem_cache *s)
{
+ kfree(s->name);
kfree(s);
}

@@ -3117,6 +3118,19 @@ void __init kmem_cache_init(void)
slab_state = UP;

/* Provide the correct kmalloc names now that the caches are up */
+ kmalloc_caches[0].name = kstrdup(kmalloc_caches[0].name, GFP_NOWAIT);
+ BUG_ON(!kmalloc_caches[0].name);
+
+ if (KMALLOC_MIN_SIZE <= 32) {
+ kmalloc_caches[1].name = kstrdup(kmalloc_caches[1].name, GFP_NOWAIT);
+ BUG_ON(!kmalloc_caches[1].name);
+ }
+
+ if (KMALLOC_MIN_SIZE <= 64) {
+ kmalloc_caches[2].name = kstrdup(kmalloc_caches[2].name, GFP_NOWAIT);
+ BUG_ON(!kmalloc_caches[2].name);
+ }
+
for (i = KMALLOC_SHIFT_LOW; i < SLUB_PAGE_SHIFT; i++) {
char *s = kasprintf(GFP_NOWAIT, "kmalloc-%d", 1 << i);

@@ -3211,6 +3225,7 @@ struct kmem_cache *kmem_cache_create(const char *name, size_t size,
size_t align, unsigned long flags, void (*ctor)(void *))
{
struct kmem_cache *s;
+ char *dup_name;

if (WARN_ON(!name))
return NULL;
@@ -3234,19 +3249,25 @@ struct kmem_cache *kmem_cache_create(const char *name, size_t size,
return s;
}

+ dup_name = kstrdup(name, GFP_KERNEL);
+ if (!dup_name)
+ goto err;
+
s = kmalloc(kmem_size, GFP_KERNEL);
if (s) {
- if (kmem_cache_open(s, GFP_KERNEL, name,
+ if (kmem_cache_open(s, GFP_KERNEL, dup_name,
size, align, flags, ctor)) {
list_add(&s->list, &slab_caches);
if (sysfs_slab_add(s)) {
list_del(&s->list);
+ kfree(dup_name);
kfree(s);
goto err;
}
up_write(&slub_lock);
return s;
}
+ kfree(dup_name);
kfree(s);
}
up_write(&slub_lock);
@@ -4377,6 +4398,7 @@ static void kmem_cache_release(struct kobject *kobj)
{
struct kmem_cache *s = to_slab(kobj);

+ kfree(s->name);
kfree(s);
}

--
1.6.3.3