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authorLaura Abbott <labbott@redhat.com>2019-07-31 15:32:40 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2019-07-31 13:16:06 -0700
commit1b7e816fc80e668f0ccc8542cec20b9259abace1 (patch)
tree6cbfdadc46ce33327cb71f2d61ecb296130e0f1c /mm/slub.c
parentd2eee9fca172d0d010ef3060cdc971e0b079b87f (diff)
mm: slub: Fix slab walking for init_on_free
To properly clear the slab on free with slab_want_init_on_free, we walk the list of free objects using get_freepointer/set_freepointer. The value we get from get_freepointer may not be valid. This isn't an issue since an actual value will get written later but this means there's a chance of triggering a bug if we use this value with set_freepointer: kernel BUG at mm/slub.c:306! invalid opcode: 0000 [#1] PREEMPT PTI CPU: 0 PID: 0 Comm: swapper Not tainted 5.2.0-05754-g6471384a #4 RIP: 0010:kfree+0x58a/0x5c0 Code: 48 83 05 78 37 51 02 01 0f 0b 48 83 05 7e 37 51 02 01 48 83 05 7e 37 51 02 01 48 83 05 7e 37 51 02 01 48 83 05 d6 37 51 02 01 <0f> 0b 48 83 05 d4 37 51 02 01 48 83 05 d4 37 51 02 01 48 83 05 d4 RSP: 0000:ffffffff82603d90 EFLAGS: 00010002 RAX: ffff8c3976c04320 RBX: ffff8c3976c04300 RCX: 0000000000000000 RDX: ffff8c3976c04300 RSI: 0000000000000000 RDI: ffff8c3976c04320 RBP: ffffffff82603db8 R08: 0000000000000000 R09: 0000000000000000 R10: ffff8c3976c04320 R11: ffffffff8289e1e0 R12: ffffd52cc8db0100 R13: ffff8c3976c01a00 R14: ffffffff810f10d4 R15: ffff8c3976c04300 FS: 0000000000000000(0000) GS:ffffffff8266b000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffff8c397ffff000 CR3: 0000000125020000 CR4: 00000000000406b0 Call Trace: apply_wqattrs_prepare+0x154/0x280 apply_workqueue_attrs_locked+0x4e/0xe0 apply_workqueue_attrs+0x36/0x60 alloc_workqueue+0x25a/0x6d0 workqueue_init_early+0x246/0x348 start_kernel+0x3c7/0x7ec x86_64_start_reservations+0x40/0x49 x86_64_start_kernel+0xda/0xe4 secondary_startup_64+0xb6/0xc0 Modules linked in: ---[ end trace f67eb9af4d8d492b ]--- Fix this by ensuring the value we set with set_freepointer is either NULL or another value in the chain. Reported-by: kernel test robot <rong.a.chen@intel.com> Signed-off-by: Laura Abbott <labbott@redhat.com> Fixes: 6471384af2a6 ("mm: security: introduce init_on_alloc=1 and init_on_free=1 boot options") Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/slub.c')
-rw-r--r--mm/slub.c8
1 files changed, 6 insertions, 2 deletions
diff --git a/mm/slub.c b/mm/slub.c
index e6c030e47364..8834563cdb4b 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1432,7 +1432,9 @@ 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))
+ if (slab_want_init_on_free(s)) {
+ void *p = NULL;
+
do {
object = next;
next = get_freepointer(s, object);
@@ -1445,8 +1447,10 @@ 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, next);
+ set_freepointer(s, object, p);
+ p = object;
} while (object != old_tail);
+ }
/*
* Compiler cannot detect this function can be removed if slab_free_hook()