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authorJan Kara <jack@suse.cz>2020-02-10 15:43:16 +0100
committerTheodore Ts'o <tytso@mit.edu>2020-02-13 11:56:19 -0500
commit48a34311953d921235f4d7bbd2111690d2e469cf (patch)
tree0a08d9ba96ed1a462da2c418caff73507cbe0a86 /fs/ext4/namei.c
parent4f97a68192bd33b9963b400759cef0ca5963af00 (diff)
ext4: fix checksum errors with indexed dirs
DIR_INDEX has been introduced as a compat ext4 feature. That means that even kernels / tools that don't understand the feature may modify the filesystem. This works because for kernels not understanding indexed dir format, internal htree nodes appear just as empty directory entries. Index dir aware kernels then check the htree structure is still consistent before using the data. This all worked reasonably well until metadata checksums were introduced. The problem is that these effectively made DIR_INDEX only ro-compatible because internal htree nodes store checksums in a different place than normal directory blocks. Thus any modification ignorant to DIR_INDEX (or just clearing EXT4_INDEX_FL from the inode) will effectively cause checksum mismatch and trigger kernel errors. So we have to be more careful when dealing with indexed directories on filesystems with checksumming enabled. 1) We just disallow loading any directory inodes with EXT4_INDEX_FL when DIR_INDEX is not enabled. This is harsh but it should be very rare (it means someone disabled DIR_INDEX on existing filesystem and didn't run e2fsck), e2fsck can fix the problem, and we don't want to answer the difficult question: "Should we rather corrupt the directory more or should we ignore that DIR_INDEX feature is not set?" 2) When we find out htree structure is corrupted (but the filesystem and the directory should in support htrees), we continue just ignoring htree information for reading but we refuse to add new entries to the directory to avoid corrupting it more. Link: https://lore.kernel.org/r/20200210144316.22081-1-jack@suse.cz Fixes: dbe89444042a ("ext4: Calculate and verify checksums for htree nodes") Reviewed-by: Andreas Dilger <adilger@dilger.ca> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Theodore Ts'o <tytso@mit.edu> Cc: stable@kernel.org
Diffstat (limited to 'fs/ext4/namei.c')
-rw-r--r--fs/ext4/namei.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 129d2ebae00d..ceff4b4b1877 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -2213,6 +2213,13 @@ static int ext4_add_entry(handle_t *handle, struct dentry *dentry,
retval = ext4_dx_add_entry(handle, &fname, dir, inode);
if (!retval || (retval != ERR_BAD_DX_DIR))
goto out;
+ /* Can we just ignore htree data? */
+ if (ext4_has_metadata_csum(sb)) {
+ EXT4_ERROR_INODE(dir,
+ "Directory has corrupted htree index.");
+ retval = -EFSCORRUPTED;
+ goto out;
+ }
ext4_clear_inode_flag(dir, EXT4_INODE_INDEX);
dx_fallback++;
ext4_mark_inode_dirty(handle, dir);