The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From afd09b617db3786b6ef3dc43e28fe728cfea84df Mon Sep 17 00:00:00 2001

From: Alexey Makhalov amakhalov@vmware.com Date: Fri, 21 May 2021 07:55:33 +0000 Subject: [PATCH] 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: https://lore.kernel.org/r/20210521075533.95732-1-amakhalov@vmware.com Signed-off-by: Alexey Makhalov amakhalov@vmware.com Signed-off-by: Theodore Ts'o tytso@mit.edu Cc: stable@kernel.org

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", blocksize); + 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 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent) kfree(get_qf_name(sb, sbi, i)); #endif fscrypt_free_dummy_policy(&sbi->s_dummy_enc_policy); - ext4_blkdev_remove(sbi); + /* ext4_blkdev_remove() calls kill_bdev(), release bh before it. */ brelse(bh); + ext4_blkdev_remove(sbi); out_fail: sb->s_fs_info = NULL; kfree(sbi->s_blockgroup_lock);