From 209f5484ef126134f2d2f322246b0e4faf3c1fbd Mon Sep 17 00:00:00 2001 From: "Darrick J. Wong" Date: Tue, 14 Oct 2014 02:35:49 -0400 Subject: [PATCH] ext4: check s_chksum_driver when looking for bg csum presence commit 813d32f91333e4c33d5a19b67167c4bae42dae75 upstream. Convert the ext4_has_group_desc_csum predicate to look for a checksum driver instead of the metadata_csum flag and change the bg checksum calculation function to look for GDT_CSUM before taking the crc16 path. Without this patch, if we mount with ^uninit_bg,^metadata_csum and later metadata_csum gets turned on by accident, the block group checksum functions will incorrectly assume that checksumming is enabled (metadata_csum) but that crc16 should be used (!s_chksum_driver). This is totally wrong, so fix the predicate and the checksum formula selection. (Granted, if the metadata_csum feature bit gets enabled on a live FS then something underhanded is going on, but we could at least avoid writing garbage into the on-disk fields.) Signed-off-by: Darrick J. Wong Signed-off-by: Theodore Ts'o Reviewed-by: Dmitry Monakhov Signed-off-by: Greg Kroah-Hartman --- fs/ext4/ext4.h | 4 ++-- fs/ext4/super.c | 4 ++++ 2 files changed, 6 insertions(+), 2 deletions(-) diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 3891475e22f7..e4c4ac07cc32 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -2261,8 +2261,8 @@ extern int ext4_register_li_request(struct super_block *sb, static inline int ext4_has_group_desc_csum(struct super_block *sb) { return EXT4_HAS_RO_COMPAT_FEATURE(sb, - EXT4_FEATURE_RO_COMPAT_GDT_CSUM | - EXT4_FEATURE_RO_COMPAT_METADATA_CSUM); + EXT4_FEATURE_RO_COMPAT_GDT_CSUM) || + (EXT4_SB(sb)->s_chksum_driver != NULL); } static inline ext4_fsblk_t ext4_blocks_count(struct ext4_super_block *es) diff --git a/fs/ext4/super.c b/fs/ext4/super.c index a1b780abdf18..21a0b43a7d31 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -1950,6 +1950,10 @@ static __le16 ext4_group_desc_csum(struct ext4_sb_info *sbi, __u32 block_group, } /* old crc16 code */ + if (!(sbi->s_es->s_feature_ro_compat & + cpu_to_le32(EXT4_FEATURE_RO_COMPAT_GDT_CSUM))) + return 0; + offset = offsetof(struct ext4_group_desc, bg_checksum); crc = crc16(~0, sbi->s_es->s_uuid, sizeof(sbi->s_es->s_uuid)); -- 2.20.1