From 65eddc0b45fcf8d2ca2608fed6e2f1de36086420 Mon Sep 17 00:00:00 2001
From: Eric Biggers <ebiggers@google.com>
Date: Mon, 14 Aug 2023 11:29:01 -0700
Subject: [PATCH] ext4: reject casefold inode flag without casefold feature
commit 8216776ccff6fcd40e3fdaa109aa4150ebe760b3 upstream.
It is invalid for the casefold inode flag to be set without the casefold
superblock feature flag also being set. e2fsck already considers this
case to be invalid and handles it by offering to clear the casefold flag
on the inode. __ext4_iget() also already considered this to be invalid,
sort of, but it only got so far as logging an error message; it didn't
actually reject the inode. Make it reject the inode so that other code
doesn't have to handle this case. This matches what f2fs does.
Note: we could check 's_encoding != NULL' instead of
ext4_has_feature_casefold(). This would make the check robust against
the casefold feature being enabled by userspace writing to the page
cache of the mounted block device. However, it's unsolvable in general
for filesystems to be robust against concurrent writes to the page cache
of the mounted block device. Though this very particular scenario
involving the casefold feature is solvable, we should not pretend that
we can support this model, so let's just check the casefold feature.
tune2fs already forbids enabling casefold on a mounted filesystem.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20230814182903.37267-2-ebiggers@kernel.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/ext4/inode.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 93a1c22048de6..7aa0a88733982 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5101,9 +5101,12 @@ struct inode *__ext4_iget(struct super_block *sb, unsigned long ino,
"iget: bogus i_mode (%o)", inode->i_mode);
goto bad_inode;
}
- if (IS_CASEFOLDED(inode) && !ext4_has_feature_casefold(inode->i_sb))
+ if (IS_CASEFOLDED(inode) && !ext4_has_feature_casefold(inode->i_sb)) {
ext4_error_inode(inode, function, line, 0,
"casefold flag without casefold feature");
+ ret = -EFSCORRUPTED;
+ goto bad_inode;
+ }
if ((err_str = check_igot_inode(inode, flags)) != NULL) {
ext4_error_inode(inode, function, line, 0, err_str);
ret = -EFSCORRUPTED;
--
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