diff options
| author | Theodore Ts'o <tytso@mit.edu> | 2021-07-02 12:45:02 -0400 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2021-07-08 08:36:09 -0400 |
| commit | 61bb4a1c417e5b95d9edb4f887f131de32e419cb (patch) | |
| tree | d51138e82d0fbc32dcd728bd6317646ea0b4ba1b /fs/ext4/mmp.c | |
| parent | cd84bbbac12a173a381a64c6ec8b76a5277b87b5 (diff) | |
ext4: fix possible UAF when remounting r/o a mmp-protected file system
After commit 618f003199c6 ("ext4: fix memory leak in
ext4_fill_super"), after the file system is remounted read-only, there
is a race where the kmmpd thread can exit, causing sbi->s_mmp_tsk to
point at freed memory, which the call to ext4_stop_mmpd() can trip
over.
Fix this by only allowing kmmpd() to exit when it is stopped via
ext4_stop_mmpd().
Link: https://lore.kernel.org/r/20210707002433.3719773-1-tytso@mit.edu
Reported-by: Ye Bin <yebin10@huawei.com>
Bug-Report-Link: <20210629143603.2166962-1-yebin10@huawei.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>
Diffstat (limited to 'fs/ext4/mmp.c')
| -rw-r--r-- | fs/ext4/mmp.c | 31 |
1 files changed, 15 insertions, 16 deletions
diff --git a/fs/ext4/mmp.c b/fs/ext4/mmp.c index 6cb598b549ca..bc364c119af6 100644 --- a/fs/ext4/mmp.c +++ b/fs/ext4/mmp.c @@ -156,7 +156,12 @@ static int kmmpd(void *data) memcpy(mmp->mmp_nodename, init_utsname()->nodename, sizeof(mmp->mmp_nodename)); - while (!kthread_should_stop()) { + while (!kthread_should_stop() && !sb_rdonly(sb)) { + if (!ext4_has_feature_mmp(sb)) { + ext4_warning(sb, "kmmpd being stopped since MMP feature" + " has been disabled."); + goto wait_to_exit; + } if (++seq > EXT4_MMP_SEQ_MAX) seq = 1; @@ -177,16 +182,6 @@ static int kmmpd(void *data) failed_writes++; } - if (!(le32_to_cpu(es->s_feature_incompat) & - EXT4_FEATURE_INCOMPAT_MMP)) { - ext4_warning(sb, "kmmpd being stopped since MMP feature" - " has been disabled."); - goto exit_thread; - } - - if (sb_rdonly(sb)) - break; - diff = jiffies - last_update_time; if (diff < mmp_update_interval * HZ) schedule_timeout_interruptible(mmp_update_interval * @@ -207,7 +202,7 @@ static int kmmpd(void *data) ext4_error_err(sb, -retval, "error reading MMP data: %d", retval); - goto exit_thread; + goto wait_to_exit; } mmp_check = (struct mmp_struct *)(bh_check->b_data); @@ -221,7 +216,7 @@ static int kmmpd(void *data) ext4_error_err(sb, EBUSY, "abort"); put_bh(bh_check); retval = -EBUSY; - goto exit_thread; + goto wait_to_exit; } put_bh(bh_check); } @@ -244,7 +239,13 @@ static int kmmpd(void *data) retval = write_mmp_block(sb, bh); -exit_thread: +wait_to_exit: + while (!kthread_should_stop()) { + set_current_state(TASK_INTERRUPTIBLE); + if (!kthread_should_stop()) + schedule(); + } + set_current_state(TASK_RUNNING); return retval; } @@ -391,5 +392,3 @@ failed: brelse(bh); return 1; } - - |