diff options
| author | Ryusuke Konishi <konishi.ryusuke@gmail.com> | 2024-05-11 03:29:42 +0300 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2024-05-20 00:36:21 +0300 |
| commit | db3e24a02e29b507c24c0adb4d22914c65dab763 (patch) | |
| tree | d2cbd7f222886dd7d159fd9713ebc392cdf7f6f3 /fs/nilfs2 | |
| parent | 28d2188709d9c19a7c4601c6870edd9fa0527379 (diff) | |
| download | linux-db3e24a02e29b507c24c0adb4d22914c65dab763.tar.xz | |
nilfs2: make block erasure safe in nilfs_finish_roll_forward()
The implementation of writing a zero-fill block in
nilfs_finish_roll_forward() is not safe. The buffer is being cleared
without acquiring a lock or setting the uptodate flag, so theoretically,
between the time the buffer's data is cleared and the time it is written
back to the block device using sync_dirty_buffer(), that zero data can be
undone by concurrent block device reads.
Since this buffer points to a location that has been read from disk once,
the uptodate flag will most likely remain, but since it was obtained with
__getblk(), that is not guaranteed. In other words, this is exceptional,
and this function itself is not normally called (only once when mounting
after a specific pattern of unclean shutdown), so it is highly unlikely
that this will actually cause a problem.
Anyway, eliminate this potential race issue by protecting the clearing of
buffer data with a buffer lock and setting the buffer's uptodate flag
within the protected section.
Link: https://lkml.kernel.org/r/20240511002942.9608-1-konishi.ryusuke@gmail.com
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'fs/nilfs2')
| -rw-r--r-- | fs/nilfs2/recovery.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/fs/nilfs2/recovery.c b/fs/nilfs2/recovery.c index 020f304c600e..b638dc06df2f 100644 --- a/fs/nilfs2/recovery.c +++ b/fs/nilfs2/recovery.c @@ -702,8 +702,12 @@ static void nilfs_finish_roll_forward(struct the_nilfs *nilfs, if (WARN_ON(!bh)) return; /* should never happen */ + lock_buffer(bh); memset(bh->b_data, 0, bh->b_size); + set_buffer_uptodate(bh); set_buffer_dirty(bh); + unlock_buffer(bh); + err = sync_dirty_buffer(bh); if (unlikely(err)) nilfs_warn(nilfs->ns_sb, |