diff options
authorAlexey Makhalov <>2021-05-21 07:55:33 +0000
committerTheodore Ts'o <>2021-06-06 10:10:23 -0400
commitafd09b617db3786b6ef3dc43e28fe728cfea84df (patch)
parenta7ba36bc94f20b6c77f16364b9a23f582ea8faac (diff)
ext4: fix memory leak in ext4_fill_super
Buffer head references must be released before calling kill_bdev(); otherwise the buffer head (and its page referenced by b_data) will not be freed by kill_bdev, and subsequently that bh will be leaked. If blocksizes differ, sb_set_blocksize() will kill current buffers and page cache by using kill_bdev(). And then super block will be reread again but using correct blocksize this time. sb_set_blocksize() didn't fully free superblock page and buffer head, and being busy, they were not freed and instead leaked. This can easily be reproduced by calling an infinite loop of: systemctl start <ext4_on_lvm>.mount, and systemctl stop <ext4_on_lvm>.mount ... since systemd creates a cgroup for each slice which it mounts, and the bh leak get amplified by a dying memory cgroup that also never gets freed, and memory consumption is much more easily noticed. Fixes: ce40733ce93d ("ext4: Check for return value from sb_set_blocksize") Fixes: ac27a0ec112a ("ext4: initial copy of files from ext3") Link: Signed-off-by: Alexey Makhalov <> Signed-off-by: Theodore Ts'o <> Cc:
1 files changed, 9 insertions, 2 deletions
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 886e0d518668..f66c7301b53a 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -4462,14 +4462,20 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
if (sb->s_blocksize != blocksize) {
+ /*
+ * bh must be released before kill_bdev(), otherwise
+ * it won't be freed and its page also. kill_bdev()
+ * is called by sb_set_blocksize().
+ */
+ brelse(bh);
/* Validate the filesystem blocksize */
if (!sb_set_blocksize(sb, blocksize)) {
ext4_msg(sb, KERN_ERR, "bad block size %d",
+ bh = NULL;
goto failed_mount;
- brelse(bh);
logical_sb_block = sb_block * EXT4_MIN_BLOCK_SIZE;
offset = do_div(logical_sb_block, blocksize);
bh = ext4_sb_bread_unmovable(sb, logical_sb_block);
@@ -5202,8 +5208,9 @@ failed_mount:
kfree(get_qf_name(sb, sbi, i));
- ext4_blkdev_remove(sbi);
+ /* ext4_blkdev_remove() calls kill_bdev(), release bh before it. */
+ ext4_blkdev_remove(sbi);
sb->s_fs_info = NULL;