From 32d1839e56a71630b0817130e2f67f7ec04bcba7 Mon Sep 17 00:00:00 2001 From: Alexey Makhalov Date: Fri, 21 May 2021 07:55:33 +0000 Subject: [PATCH] ext4: fix memory leak in ext4_fill_super BugLink: https://bugs.launchpad.net/bugs/1933691 commit afd09b617db3786b6ef3dc43e28fe728cfea84df upstream. 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 .mount, and systemctl stop .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 Signed-off-by: Theodore Ts'o Cc: stable@kernel.org Signed-off-by: Greg Kroah-Hartman Signed-off-by: Kamal Mostafa Signed-off-by: Kelsey Skunberg --- fs/ext4/super.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/fs/ext4/super.c b/fs/ext4/super.c index ce883bed1355..f44d605fc61c 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -4449,14 +4449,20 @@ 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); @@ -5176,8 +5182,9 @@ failed_mount: 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); -- 2.39.5