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
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
On Tue, Mar 28, 2017 at 9:28 AM, Alexander Potapenko <[email protected]> wrote:
> 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.
I think the following would be better (pardon any whitespace damage
via gmail...):
diff --git a/fs/buffer.c b/fs/buffer.c
index 161be58c5cb0..20292b858b61 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -3021,11 +3021,11 @@ EXPORT_SYMBOL(block_write_full_page);
sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
get_block_t *get_block)
{
- struct buffer_head tmp;
struct inode *inode = mapping->host;
- tmp.b_state = 0;
- tmp.b_blocknr = 0;
- tmp.b_size = i_blocksize(inode);
+ struct buffer_head tmp = {
+ .b_size = i_blocksize(inode);
+ };
+
get_block(inode, block, &tmp, 0);
return tmp.b_blocknr;
}
This will keep all unspecified fields zero-initialized. (i.e. a more
robust fix than just a single zero-initialization being added)
-Kees
--
Kees Cook
Pixel Security
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