ext4: fix memory leak in ext4_fill_super

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@syzkaller.appspotmail.com
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
Link: https://lore.kernel.org/r/20210430185046.15742-1-paskripkin@gmail.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 639ab5405d6a6823505e090d66f67ab326c58783..2b51cbee39076c3d05a67fc5925015c11e4aa477 100644 (file)
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1488,6 +1488,7 @@ 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;
@@ -3720,6 +3721,9 @@ extern struct ext4_io_end_vec *ext4_last_io_end_vec(ext4_io_end_t *io_end);
 /* 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;
 

diff --git a/fs/ext4/mmp.c b/fs/ext4/mmp.c
index 68fbeedd627bc5fab86ab865fa0a739cfe3764c6..6cb598b549ca169af7bc533c87298ff369b0d539 100644 (file)
--- a/fs/ext4/mmp.c
+++ b/fs/ext4/mmp.c
@@ -127,9 +127,9 @@ void __dump_mmp_msg(struct super_block *sb, struct mmp_struct *mmp,
  */
 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 super_block *sb,
        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;

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index d29f6aa7d96eede2f7888e8ce29a59f253393ffb..b6fe1a027c78b9a6080f7352fac4da2e460c3c5a 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1245,8 +1245,8 @@ static void ext4_put_super(struct super_block *sb)
        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;
        /*
@@ -5186,8 +5186,7 @@ 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);
@@ -5989,8 +5988,7 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
                                 */
                                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) ||