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stackdepot: fix mempolicy use-after-free
author
Vegard Nossum
<vegard.nossum@oracle.com>
Sat, 10 Sep 2016 10:33:59 +0000
(20:33 +1000)
committer
Stephen Rothwell
<sfr@canb.auug.org.au>
Sat, 10 Sep 2016 10:33:59 +0000
(20:33 +1000)
This patch fixes the following:
BUG: KASAN: use-after-free in alloc_pages_current+0x363/0x370 at addr
ffff88010b48102c
Read of size 2 by task trinity-c2/15425
CPU: 0 PID: 15425 Comm: trinity-c2 Not tainted 4.8.0-rc2+ #140
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
rel-1.9.3-0-ge2fc41e
-prebuilt.qemu-proje
ct.org 04/01/2014
ffff88010b481040
ffff88010b557650
ffffffff81f08d11
ffff88011a40d380
ffff88010b481028
ffff88010b557678
ffffffff815dac7c
ffff88010b557708
ffff88010b481028
ffff88011a40d380
ffff88010b5576f8
ffffffff815daf15
Call Trace:
[<
ffffffff81f08d11
>] dump_stack+0x65/0x84
[<
ffffffff815dac7c
>] kasan_object_err+0x1c/0x70
[<
ffffffff815daf15
>] kasan_report_error+0x1f5/0x4c0
[<
ffffffff815db2fe
>] __asan_report_load2_noabort+0x3e/0x40
[<
ffffffff815cb903
>] alloc_pages_current+0x363/0x370 <---- use-after-free
[<
ffffffff81fa9954
>] depot_save_stack+0x3f4/0x490
[<
ffffffff815d9bb5
>] save_stack+0xb5/0xd0
[<
ffffffff815da211
>] kasan_slab_free+0x71/0xb0
[<
ffffffff815d6643
>] kmem_cache_free+0xa3/0x290
[<
ffffffff815c8149
>] __mpol_put+0x19/0x20 <---- free
[<
ffffffff81260635
>] do_exit+0x1515/0x2b70
[<
ffffffff81261dc4
>] do_group_exit+0xf4/0x2f0
[<
ffffffff81281c5d
>] get_signal+0x53d/0x1120
[<
ffffffff8119e993
>] do_signal+0x83/0x1e20
[<
ffffffff810027af
>] exit_to_usermode_loop+0xaf/0x140
[<
ffffffff810051e4
>] syscall_return_slowpath+0x144/0x170
[<
ffffffff83ae406f
>] ret_from_fork+0x2f/0x40
Read of size 2 by task trinity-c2/15425
The problem is that we may be calling alloc_pages() in a code path where
current->mempolicy has already been freed.
By passing __GFP_THISNODE we will always use default_mempolicy (which
cannot be freed).
Link:
https://lkml.org/lkml/2016/7/29/277
Link:
https://github.com/google/kasan/issues/35
Link:
http://lkml.kernel.org/r/1471603265-31804-1-git-send-email-vegard.nossum@oracle.com
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
lib/stackdepot.c
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diff --git
a/lib/stackdepot.c
b/lib/stackdepot.c
index 60f77f1d470a0589ccdeacbb52a9eb45a8a1cec1..da015cda4f4baf68b4007a91a8d40287fe7f48b5 100644
(file)
--- a/
lib/stackdepot.c
+++ b/
lib/stackdepot.c
@@
-243,6
+243,12
@@
depot_stack_handle_t depot_save_stack(struct stack_trace *trace,
alloc_flags &= ~GFP_ZONEMASK;
alloc_flags &= (GFP_ATOMIC | GFP_KERNEL);
alloc_flags |= __GFP_NOWARN;
+ /*
+ * Avoid using current->mempolicy which may already have
+ * been freed -- we may be in the process of saving the
+ * stack for exactly that __mpol_put() call.
+ */
+ alloc_flags |= __GFP_THISNODE;
page = alloc_pages(alloc_flags, STACK_ALLOC_ORDER);
if (page)
prealloc = page_address(page);
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