KMSAN (KernelMemorySanitizer, a new error detection tool) reports use of
uninitialized memory in ext4_update_bh_state():
==================================================================
BUG: KMSAN: use of unitialized memory
CPU: 3 PID: 1 Comm: swapper/0 Tainted: G B 4.8.0-rc6+ #597
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs
01/01/2011
0000000000000282 ffff88003cc96f68 ffffffff81f30856 0000003000000008
ffff88003cc96f78 0000000000000096 ffffffff8169742a ffff88003cc96ff8
ffffffff812fc1fc 0000000000000008 ffff88003a1980e8 0000000100000000
Call Trace:
[< inline >] __dump_stack lib/dump_stack.c:15
[<ffffffff81f30856>] dump_stack+0xa6/0xc0 lib/dump_stack.c:51
[<ffffffff812fc1fc>] kmsan_report+0x1ec/0x300 mm/kmsan/kmsan.c:?
[<ffffffff812fc33b>] __msan_warning+0x2b/0x40 ??:?
[< inline >] ext4_update_bh_state fs/ext4/inode.c:727
[<ffffffff8169742a>] _ext4_get_block+0x6ca/0x8a0 fs/ext4/inode.c:759
[<ffffffff81696d4c>] ext4_get_block+0x8c/0xa0 fs/ext4/inode.c:769
[<ffffffff814a2d36>] generic_block_bmap+0x246/0x2b0 fs/buffer.c:2991
[<ffffffff816ca30e>] ext4_bmap+0x5ee/0x660 fs/ext4/inode.c:3177
...
origin description: ----tmp@generic_block_bmap
==================================================================
(the line numbers are relative to 4.8-rc6, but the bug persists
upstream)
The local |tmp| is created in generic_block_bmap() and then passed into
ext4_bmap() => ext4_get_block() => _ext4_get_block() =>
ext4_update_bh_state(). Along the way tmp.b_page is never initialized
before ext4_update_bh_state() checks its value.
Signed-off-by: Alexander Potapenko <[email protected]>
---
fs/buffer.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/fs/buffer.c b/fs/buffer.c
index d21771f..3fb104e 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -3029,6 +3029,7 @@ sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
tmp.b_state = 0;
tmp.b_blocknr = 0;
tmp.b_size = 1 << inode->i_blkbits;
+ tmp.b_page = NULL;
get_block(inode, block, &tmp, 0);
return tmp.b_blocknr;
}
--
2.8.0.rc3.226.g39d4020
On Wed, Jan 18, 2017 at 5:32 PM, Theodore Ts'o <[email protected]> wrote:
> On Thu, Dec 22, 2016 at 01:30:15PM +0100, Alexander Potapenko wrote:
>> KMSAN (KernelMemorySanitizer, a new error detection tool) reports use of
>> uninitialized memory in ext4_update_bh_state():
>>
>> ==================================================================
>> BUG: KMSAN: use of unitialized memory
>> CPU: 3 PID: 1 Comm: swapper/0 Tainted: G B 4.8.0-rc6+ #597
>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs
>> 01/01/2011
>> 0000000000000282 ffff88003cc96f68 ffffffff81f30856 0000003000000008
>> ffff88003cc96f78 0000000000000096 ffffffff8169742a ffff88003cc96ff8
>> ffffffff812fc1fc 0000000000000008 ffff88003a1980e8 0000000100000000
>> Call Trace:
>> [< inline >] __dump_stack lib/dump_stack.c:15
>> [<ffffffff81f30856>] dump_stack+0xa6/0xc0 lib/dump_stack.c:51
>> [<ffffffff812fc1fc>] kmsan_report+0x1ec/0x300 mm/kmsan/kmsan.c:?
>> [<ffffffff812fc33b>] __msan_warning+0x2b/0x40 ??:?
>> [< inline >] ext4_update_bh_state fs/ext4/inode.c:727
>> [<ffffffff8169742a>] _ext4_get_block+0x6ca/0x8a0 fs/ext4/inode.c:759
>> [<ffffffff81696d4c>] ext4_get_block+0x8c/0xa0 fs/ext4/inode.c:769
>> [<ffffffff814a2d36>] generic_block_bmap+0x246/0x2b0 fs/buffer.c:2991
>> [<ffffffff816ca30e>] ext4_bmap+0x5ee/0x660 fs/ext4/inode.c:3177
>> ...
>> origin description: ----tmp@generic_block_bmap
>> ==================================================================
>>
>> (the line numbers are relative to 4.8-rc6, but the bug persists
>> upstream)
>>
>> The local |tmp| is created in generic_block_bmap() and then passed into
>> ext4_bmap() => ext4_get_block() => _ext4_get_block() =>
>> ext4_update_bh_state(). Along the way tmp.b_page is never initialized
>> before ext4_update_bh_state() checks its value.
>>
>> Signed-off-by: Alexander Potapenko <[email protected]>
>
> This is a one-line fix to fs/buffer.c; but I've investigated, and
> since it only affects ext4, and no one else has responded, I'll take
> the change through the ext4 git tree.
>
> Thanks!!
>
> - Ted
Hi Ted,
any updates on this patch?
Looks like it hasn't been landed yet.
Alex
--
Alexander Potapenko
Software Engineer
Google Germany GmbH
Erika-Mann-Straße, 33
80636 München
Geschäftsführer: Matthew Scott Sucherman, Paul Terence Manicle
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg
Hi Theodore,
Looks like the patch hasn't been landed yet, could you please revisit it?
Thanks,
Alex
On Wed, Jan 18, 2017 at 5:32 PM, Theodore Ts'o <[email protected]> wrote:
> On Thu, Dec 22, 2016 at 01:30:15PM +0100, Alexander Potapenko wrote:
>> KMSAN (KernelMemorySanitizer, a new error detection tool) reports use of
>> uninitialized memory in ext4_update_bh_state():
>>
>> ==================================================================
>> BUG: KMSAN: use of unitialized memory
>> CPU: 3 PID: 1 Comm: swapper/0 Tainted: G B 4.8.0-rc6+ #597
>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs
>> 01/01/2011
>> 0000000000000282 ffff88003cc96f68 ffffffff81f30856 0000003000000008
>> ffff88003cc96f78 0000000000000096 ffffffff8169742a ffff88003cc96ff8
>> ffffffff812fc1fc 0000000000000008 ffff88003a1980e8 0000000100000000
>> Call Trace:
>> [< inline >] __dump_stack lib/dump_stack.c:15
>> [<ffffffff81f30856>] dump_stack+0xa6/0xc0 lib/dump_stack.c:51
>> [<ffffffff812fc1fc>] kmsan_report+0x1ec/0x300 mm/kmsan/kmsan.c:?
>> [<ffffffff812fc33b>] __msan_warning+0x2b/0x40 ??:?
>> [< inline >] ext4_update_bh_state fs/ext4/inode.c:727
>> [<ffffffff8169742a>] _ext4_get_block+0x6ca/0x8a0 fs/ext4/inode.c:759
>> [<ffffffff81696d4c>] ext4_get_block+0x8c/0xa0 fs/ext4/inode.c:769
>> [<ffffffff814a2d36>] generic_block_bmap+0x246/0x2b0 fs/buffer.c:2991
>> [<ffffffff816ca30e>] ext4_bmap+0x5ee/0x660 fs/ext4/inode.c:3177
>> ...
>> origin description: ----tmp@generic_block_bmap
>> ==================================================================
>>
>> (the line numbers are relative to 4.8-rc6, but the bug persists
>> upstream)
>>
>> The local |tmp| is created in generic_block_bmap() and then passed into
>> ext4_bmap() => ext4_get_block() => _ext4_get_block() =>
>> ext4_update_bh_state(). Along the way tmp.b_page is never initialized
>> before ext4_update_bh_state() checks its value.
>>
>> Signed-off-by: Alexander Potapenko <[email protected]>
>
> This is a one-line fix to fs/buffer.c; but I've investigated, and
> since it only affects ext4, and no one else has responded, I'll take
> the change through the ext4 git tree.
>
> Thanks!!
>
> - Ted
--
Alexander Potapenko
Software Engineer
Google Germany GmbH
Erika-Mann-Straße, 33
80636 München
Geschäftsführer: Matthew Scott Sucherman, Paul Terence Manicle
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg
On Mon, May 22, 2017 at 10:58:45AM -0700, Kees Cook wrote:
> > any updates on this patch?
> > Looks like it hasn't been landed yet.
>
> I think the following would be better (pardon any whitespace damage
> via gmail...):
>
I've applied Kees suggested change to the ext4 git tree.
- Ted