From: Pavel Skripkin <paskripkin@xxxxxxxxx> commit 618f003199c6188e01472b03cdbba227f1dc5f24 upstream. static int kthread(void *_create) will return -ENOMEM or -EINTR in case of internal failure or kthread_stop() call happens before threadfn call. To prevent fancy error checking and make code more straightforward we moved all cleanup code out of kmmpd threadfn. Also, dropped struct mmpd_data at all. Now struct super_block is a threadfn data and struct buffer_head embedded into struct ext4_sb_info. Reported-by: syzbot+d9e482e303930fa4f6ff@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Pavel Skripkin <paskripkin@xxxxxxxxx> Link: https://lore.kernel.org/r/20210430185046.15742-1-paskripkin@xxxxxxxxx Signed-off-by: Theodore Ts'o <tytso@xxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/ext4/ext4.h | 4 ++++ fs/ext4/mmp.c | 28 +++++++++++++--------------- fs/ext4/super.c | 10 ++++------ 3 files changed, 21 insertions(+), 21 deletions(-) --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -1490,6 +1490,7 @@ struct ext4_sb_info { struct kobject s_kobj; struct completion s_kobj_unregister; struct super_block *s_sb; + struct buffer_head *s_mmp_bh; /* Journaling */ struct journal_s *s_journal; @@ -3663,6 +3664,9 @@ extern struct ext4_io_end_vec *ext4_last /* mmp.c */ extern int ext4_multi_mount_protect(struct super_block *, ext4_fsblk_t); +/* mmp.c */ +extern void ext4_stop_mmpd(struct ext4_sb_info *sbi); + /* verity.c */ extern const struct fsverity_operations ext4_verityops; --- a/fs/ext4/mmp.c +++ b/fs/ext4/mmp.c @@ -127,9 +127,9 @@ void __dump_mmp_msg(struct super_block * */ static int kmmpd(void *data) { - struct super_block *sb = ((struct mmpd_data *) data)->sb; - struct buffer_head *bh = ((struct mmpd_data *) data)->bh; + struct super_block *sb = (struct super_block *) data; struct ext4_super_block *es = EXT4_SB(sb)->s_es; + struct buffer_head *bh = EXT4_SB(sb)->s_mmp_bh; struct mmp_struct *mmp; ext4_fsblk_t mmp_block; u32 seq = 0; @@ -245,12 +245,18 @@ static int kmmpd(void *data) retval = write_mmp_block(sb, bh); exit_thread: - EXT4_SB(sb)->s_mmp_tsk = NULL; - kfree(data); - brelse(bh); return retval; } +void ext4_stop_mmpd(struct ext4_sb_info *sbi) +{ + if (sbi->s_mmp_tsk) { + kthread_stop(sbi->s_mmp_tsk); + brelse(sbi->s_mmp_bh); + sbi->s_mmp_tsk = NULL; + } +} + /* * Get a random new sequence number but make sure it is not greater than * EXT4_MMP_SEQ_MAX. @@ -275,7 +281,6 @@ int ext4_multi_mount_protect(struct supe struct ext4_super_block *es = EXT4_SB(sb)->s_es; struct buffer_head *bh = NULL; struct mmp_struct *mmp = NULL; - struct mmpd_data *mmpd_data; u32 seq; unsigned int mmp_check_interval = le16_to_cpu(es->s_mmp_update_interval); unsigned int wait_time = 0; @@ -364,24 +369,17 @@ skip: goto failed; } - mmpd_data = kmalloc(sizeof(*mmpd_data), GFP_KERNEL); - if (!mmpd_data) { - ext4_warning(sb, "not enough memory for mmpd_data"); - goto failed; - } - mmpd_data->sb = sb; - mmpd_data->bh = bh; + EXT4_SB(sb)->s_mmp_bh = bh; /* * Start a kernel thread to update the MMP block periodically. */ - EXT4_SB(sb)->s_mmp_tsk = kthread_run(kmmpd, mmpd_data, "kmmpd-%.*s", + EXT4_SB(sb)->s_mmp_tsk = kthread_run(kmmpd, sb, "kmmpd-%.*s", (int)sizeof(mmp->mmp_bdevname), bdevname(bh->b_bdev, mmp->mmp_bdevname)); if (IS_ERR(EXT4_SB(sb)->s_mmp_tsk)) { EXT4_SB(sb)->s_mmp_tsk = NULL; - kfree(mmpd_data); ext4_warning(sb, "Unable to create kmmpd thread for %s.", sb->s_id); goto failed; --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -1245,8 +1245,8 @@ static void ext4_put_super(struct super_ ext4_xattr_destroy_cache(sbi->s_ea_block_cache); sbi->s_ea_block_cache = NULL; - if (sbi->s_mmp_tsk) - kthread_stop(sbi->s_mmp_tsk); + ext4_stop_mmpd(sbi); + brelse(sbi->s_sbh); sb->s_fs_info = NULL; /* @@ -5168,8 +5168,7 @@ failed_mount3a: 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); + ext4_stop_mmpd(sbi); failed_mount2: rcu_read_lock(); group_desc = rcu_dereference(sbi->s_group_desc); @@ -5967,8 +5966,7 @@ static int ext4_remount(struct super_blo */ ext4_mark_recovery_complete(sb, es); } - if (sbi->s_mmp_tsk) - kthread_stop(sbi->s_mmp_tsk); + ext4_stop_mmpd(sbi); } else { /* Make sure we can mount this feature set readwrite */ if (ext4_has_feature_readonly(sb) ||
