diff mbox

fs: Initialize tmp.b_page in generic_block_bmap()

Message ID 1482409815-89034-1-git-send-email-glider@google.com (mailing list archive)
State New, archived
Headers show

Commit Message

Alexander Potapenko Dec. 22, 2016, 12:30 p.m. UTC 
KMSAN (KernelMemorySanitizer, a new error detection tool) reports use of
uninitialized memory in ext4_update_bh_state():

Comments

Theodore Ts'o Jan. 18, 2017, 4:32 p.m. UTC | #1 
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 <glider@google.com>

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
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Alexander Potapenko March 28, 2017, 4:28 p.m. UTC | #2 
On Wed, Jan 18, 2017 at 5:32 PM, Theodore Ts'o <tytso@mit.edu> 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 <glider@google.com>
>
> 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 June 26, 2017, 10:06 a.m. UTC | #3 
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 <tytso@mit.edu> 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 <glider@google.com>
>
> 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
diff mbox

Patch

==================================================================
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 <glider@google.com>
---
 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;
 }