From b99fd73418350dea360da8311e87a6a7b0e15a4c Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Tue, 17 May 2022 13:27:55 -0400 Subject: [PATCH] ext4: filter out EXT4_FC_REPLAY from on-disk superblock field s_state commit c878bea3c9d724ddfa05a813f30de3d25a0ba83f upstream. The EXT4_FC_REPLAY bit in sbi->s_mount_state is used to indicate that we are in the middle of replay the fast commit journal. This was actually a mistake, since the sbi->s_mount_info is initialized from es->s_state. Arguably s_mount_state is misleadingly named, but the name is historical --- s_mount_state and s_state dates back to ext2. What should have been used is the ext4_{set,clear,test}_mount_flag() inline functions, which sets EXT4_MF_* bits in sbi->s_mount_flags. The problem with using EXT4_FC_REPLAY is that a maliciously corrupted superblock could result in EXT4_FC_REPLAY getting set in s_mount_state. This bypasses some sanity checks, and this can trigger a BUG() in ext4_es_cache_extent(). As a easy-to-backport-fix, filter out the EXT4_FC_REPLAY bit for now. We should eventually transition away from EXT4_FC_REPLAY to something like EXT4_MF_REPLAY. Cc: stable@kernel.org Signed-off-by: Theodore Ts'o Link: https://lore.kernel.org/r/20220420192312.1655305-1-phind.uet@gmail.com Link: https://lore.kernel.org/r/20220517174028.942119-1-tytso@mit.edu Reported-by: syzbot+c7358a3cd05ee786eb31@syzkaller.appspotmail.com Signed-off-by: Greg Kroah-Hartman --- fs/ext4/super.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 10d5ee6c3edd0..2c12ec7bd077d 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -4391,7 +4391,7 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent) sbi->s_inodes_per_block; sbi->s_desc_per_block = blocksize / EXT4_DESC_SIZE(sb); sbi->s_sbh = bh; - sbi->s_mount_state = le16_to_cpu(es->s_state); + sbi->s_mount_state = le16_to_cpu(es->s_state) & ~EXT4_FC_REPLAY; sbi->s_addr_per_block_bits = ilog2(EXT4_ADDR_PER_BLOCK(sb)); sbi->s_desc_per_block_bits = ilog2(EXT4_DESC_PER_BLOCK(sb)); @@ -5937,7 +5937,8 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data) if (err) goto restore_opts; } - sbi->s_mount_state = le16_to_cpu(es->s_state); + sbi->s_mount_state = (le16_to_cpu(es->s_state) & + ~EXT4_FC_REPLAY); err = ext4_setup_super(sb, es, 0); if (err)