Hi! I've done debugging on this issue https://syzkaller.appspot.com/bug?id=420258a304e5d92cfef6b0097f87b42506e1db08 and I want to ask you about proper way of fixing it. The problem was in case sbi->s_mmp_tsk hasn’t started at the time of kthread_stop() call. In that case allocated data won't be freed. I wrote fix patch, but I am confused about it, because I didn't find any kernel code like this. I don't think, that adding new members to struct super_block is good idea, that's why I came to that decision: diff --git a/fs/ext4/super.c b/fs/ext4/super.c index b9693680463a..9c33e97bd5c5 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -5156,8 +5156,10 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent) failed_mount3: flush_work(&sbi->s_error_work); del_timer_sync(&sbi->s_err_report); - if (sbi->s_mmp_tsk) - kthread_stop(sbi->s_mmp_tsk); + if (sbi->s_mmp_tsk) { + if (kthread_stop(sbi->s_mmp_tsk) == -EINTR) + kfree(kthread_data(sbi->s_mmp_tsk)); + } failed_mount2: rcu_read_lock(); group_desc = rcu_dereference(sbi->s_group_desc); I look forward to hearing your perspective on this patch :) With regards, Pavel Skripkin
