diff options
| author | Laura Abbott <labbott@redhat.com> | 2019-07-31 15:32:40 -0400 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-07-31 13:16:06 -0700 |
| commit | 1b7e816fc80e668f0ccc8542cec20b9259abace1 (patch) | |
| tree | 6cbfdadc46ce33327cb71f2d61ecb296130e0f1c /mm/slub.c | |
| parent | d2eee9fca172d0d010ef3060cdc971e0b079b87f (diff) | |
| download | lwn-1b7e816fc80e668f0ccc8542cec20b9259abace1.tar.gz lwn-1b7e816fc80e668f0ccc8542cec20b9259abace1.zip | |
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.c | 8 |
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() |