From: Theodore Ts'o tytso@mit.edu
commit 61bb4a1c417e5b95d9edb4f887f131de32e419cb upstream.
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 Cc: Tadeusz Struk tadeusz.struk@linaro.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/ext4/mmp.c | 31 +++++++++++++++---------------- fs/ext4/super.c | 6 +++++- 2 files changed, 20 insertions(+), 17 deletions(-)
--- 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; } - - --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -5932,7 +5932,6 @@ static int ext4_remount(struct super_blo */ ext4_mark_recovery_complete(sb, es); } - ext4_stop_mmpd(sbi); } else { /* Make sure we can mount this feature set readwrite */ if (ext4_has_feature_readonly(sb) || @@ -6046,6 +6045,9 @@ static int ext4_remount(struct super_blo if (!test_opt(sb, BLOCK_VALIDITY) && sbi->s_system_blks) ext4_release_system_zone(sb);
+ if (!ext4_has_feature_mmp(sb) || sb_rdonly(sb)) + ext4_stop_mmpd(sbi); + /* * Some options can be enabled by ext4 and/or by VFS mount flag * either way we need to make sure it matches in both *flags and @@ -6078,6 +6080,8 @@ restore_opts: for (i = 0; i < EXT4_MAXQUOTAS; i++) kfree(to_free[i]); #endif + if (!ext4_has_feature_mmp(sb) || sb_rdonly(sb)) + ext4_stop_mmpd(sbi); kfree(orig_data); return err; }