From: Jan Kara jack@suse.cz

mainline inclusion from mainline-v5.15-rc1 commit b2bbb92f7042e8075fb036bf97043339576330c3 category: bugfix bugzilla: 186203 CVE: NA

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Commit 81414b4dd48 ("ext4: remove redundant sb checksum recomputation") removed checksum recalculation after updating superblock free space / inode counters in ext4_fill_super() based on the fact that we will recalculate the checksum on superblock writeout.

That is correct assumption but until the writeout happens (which can take a long time) the checksum is incorrect in the buffer cache and if programs such as tune2fs or resize2fs is called shortly after a file system is mounted can fail. So return back the checksum recalculation and add a comment explaining why.

Fixes: 81414b4dd48f ("ext4: remove redundant sb checksum recomputation") Cc: stable@kernel.org Reported-by: Boyang Xue bxue@redhat.com Signed-off-by: Jan Kara jack@suse.cz Signed-off-by: Theodore Ts'o tytso@mit.edu Link: https://lore.kernel.org/r/20210812124737.21981-1-jack@suse.cz Signed-off-by: Zheng Liang zhengliang6@huawei.com Reviewed-by: Zhang Yi yi.zhang@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- fs/ext4/super.c | 8 ++++++++ 1 file changed, 8 insertions(+)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c index b89f431ec78d3..59637e70f9e32 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -4693,6 +4693,14 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent) err = percpu_counter_init(&sbi->s_freeinodes_counter, freei, GFP_KERNEL); } + /* + * Update the checksum after updating free space/inode + * counters. Otherwise the superblock can have an incorrect + * checksum in the buffer cache until it is written out and + * e2fsprogs programs trying to open a file system immediately + * after it is mounted can fail. + */ + ext4_superblock_csum_set(sb); if (!err) err = percpu_counter_init(&sbi->s_dirs_counter, ext4_count_dirs(sb), GFP_KERNEL);