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authorLaura Abbott <labbott@redhat.com>2019-11-15 17:34:50 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2019-11-15 18:34:00 -0800
commitaea4df4c53f754cc229edde6c5465e481311cc49 (patch)
tree7db9b37a22a3fc8c163569e5f4e1ac05dfbdaafa
parent0362f326d86c645b5e96b7dbc3ee515986ed019d (diff)
downloadlinux-sh-aea4df4c53f754cc229edde6c5465e481311cc49.tar.gz
mm: slub: really fix slab walking for init_on_free
Commit 1b7e816fc80e ("mm: slub: Fix slab walking for init_on_free") fixed one problem with the slab walking but missed a key detail: When walking the list, the head and tail pointers need to be updated since we end up reversing the list as a result. Without doing this, bulk free is broken. One way this is exposed is a NULL pointer with slub_debug=F: ============================================================================= BUG skbuff_head_cache (Tainted: G T): Object already free ----------------------------------------------------------------------------- INFO: Slab 0x000000000d2d2f8f objects=16 used=3 fp=0x0000000064309071 flags=0x3fff00000000201 BUG: kernel NULL pointer dereference, address: 0000000000000000 Oops: 0000 [#1] PREEMPT SMP PTI RIP: 0010:print_trailer+0x70/0x1d5 Call Trace: <IRQ> free_debug_processing.cold.37+0xc9/0x149 __slab_free+0x22a/0x3d0 kmem_cache_free_bulk+0x415/0x420 __kfree_skb_flush+0x30/0x40 net_rx_action+0x2dd/0x480 __do_softirq+0xf0/0x246 irq_exit+0x93/0xb0 do_IRQ+0xa0/0x110 common_interrupt+0xf/0xf </IRQ> Given we're now almost identical to the existing debugging code which correctly walks the list, combine with that. Link: https://lkml.kernel.org/r/20191104170303.GA50361@gandi.net Link: http://lkml.kernel.org/r/20191106222208.26815-1-labbott@redhat.com Fixes: 1b7e816fc80e ("mm: slub: Fix slab walking for init_on_free") Signed-off-by: Laura Abbott <labbott@redhat.com> Reported-by: Thibaut Sautereau <thibaut.sautereau@clip-os.org> Acked-by: David Rientjes <rientjes@google.com> Tested-by: Alexander Potapenko <glider@google.com> Acked-by: Alexander Potapenko <glider@google.com> Cc: Kees Cook <keescook@chromium.org> Cc: "David S. Miller" <davem@davemloft.net> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: <clipos@ssi.gouv.fr> Cc: Christoph Lameter <cl@linux.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/slub.c39
1 files changed, 9 insertions, 30 deletions
diff --git a/mm/slub.c b/mm/slub.c
index b25c807a111f..e72e802fc569 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1433,12 +1433,15 @@ static inline bool slab_free_freelist_hook(struct kmem_cache *s,
void *old_tail = *tail ? *tail : *head;
int rsize;
- if (slab_want_init_on_free(s)) {
- void *p = NULL;
+ /* Head and tail of the reconstructed freelist */
+ *head = NULL;
+ *tail = NULL;
- do {
- object = next;
- next = get_freepointer(s, object);
+ do {
+ object = next;
+ next = get_freepointer(s, object);
+
+ if (slab_want_init_on_free(s)) {
/*
* Clear the object and the metadata, but don't touch
* the redzone.
@@ -1448,29 +1451,8 @@ static inline bool slab_free_freelist_hook(struct kmem_cache *s,
: 0;
memset((char *)object + s->inuse, 0,
s->size - s->inuse - rsize);
- set_freepointer(s, object, p);
- p = object;
- } while (object != old_tail);
- }
-
-/*
- * Compiler cannot detect this function can be removed if slab_free_hook()
- * evaluates to nothing. Thus, catch all relevant config debug options here.
- */
-#if defined(CONFIG_LOCKDEP) || \
- defined(CONFIG_DEBUG_KMEMLEAK) || \
- defined(CONFIG_DEBUG_OBJECTS_FREE) || \
- defined(CONFIG_KASAN)
- next = *head;
-
- /* Head and tail of the reconstructed freelist */
- *head = NULL;
- *tail = NULL;
-
- do {
- object = next;
- next = get_freepointer(s, object);
+ }
/* If object's reuse doesn't have to be delayed */
if (!slab_free_hook(s, object)) {
/* Move object to the new freelist */
@@ -1485,9 +1467,6 @@ static inline bool slab_free_freelist_hook(struct kmem_cache *s,
*tail = NULL;
return *head != NULL;
-#else
- return true;
-#endif
}
static void *setup_object(struct kmem_cache *s, struct page *page,