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| author | Alexander Potapenko <glider@google.com> | 2017-07-05 00:56:21 -0400 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2017-07-05 00:56:21 -0400 |
| commit | 2a527d6858c246db8afc3d576dbcbff0902f933b (patch) | |
| tree | ea4a0d4c64d6437c145bf93fccb985b58cbd60be /fs/buffer.c | |
| parent | 407cd7fb83c0ebabb490190e673d8c71ee7df97e (diff) | |
| download | lwn-2a527d6858c246db8afc3d576dbcbff0902f933b.tar.gz lwn-2a527d6858c246db8afc3d576dbcbff0902f933b.zip | |
fs: generic_block_bmap(): initialize all of the fields in the temp bh
KMSAN (KernelMemorySanitizer, a new error detection tool) reports the
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.
[ Use the approach suggested by Kees Cook of initializing the whole bh
structure.]
Signed-off-by: Alexander Potapenko <glider@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'fs/buffer.c')
| -rw-r--r-- | fs/buffer.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/fs/buffer.c b/fs/buffer.c index 161be58c5cb0..a3399aa6a2bd 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; } |