Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 5.17 643/772] ext4: filter out EXT4_FC_REPLAY from on-disk superblock field s_state | Date | Tue, 7 Jun 2022 19:03:55 +0200 |
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From: Theodore Ts'o <tytso@mit.edu>
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 <tytso@mit.edu> 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 <gregkh@linuxfoundation.org> --- fs/ext4/super.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
--- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -4874,7 +4874,7 @@ static int __ext4_fill_super(struct fs_c 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)); @@ -6437,7 +6437,8 @@ static int __ext4_remount(struct fs_cont 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)
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