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authorAlexander Potapenko <glider@google.com>2017-07-05 00:56:21 -0400
committerTheodore Ts'o <tytso@mit.edu>2017-07-05 00:56:21 -0400
commit2a527d6858c246db8afc3d576dbcbff0902f933b (patch)
treeea4a0d4c64d6437c145bf93fccb985b58cbd60be /fs/buffer.c
parent407cd7fb83c0ebabb490190e673d8c71ee7df97e (diff)
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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.c8
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;
}