From 2824083db76cb9d4b7910607b367e93b02912865 Mon Sep 17 00:00:00 2001 From: Gabriel Krisman Bertazi Date: Wed, 21 Feb 2024 12:14:03 -0500 Subject: ovl: Always reject mounting over case-insensitive directories overlayfs relies on the filesystem setting DCACHE_OP_HASH or DCACHE_OP_COMPARE to reject mounting over case-insensitive directories. Since commit bb9cd9106b22 ("fscrypt: Have filesystems handle their d_ops"), we set ->d_op through a hook in ->d_lookup, which means the root dentry won't have them, causing the mount to accidentally succeed. In v6.7-rc7, the following sequence will succeed to mount, but any dentry other than the root dentry will be a "weird" dentry to ovl and fail with EREMOTE. mkfs.ext4 -O casefold lower.img mount -O loop lower.img lower mount -t overlay -o lowerdir=lower,upperdir=upper,workdir=work ovl /mnt Mounting on a subdirectory fails, as expected, because DCACHE_OP_HASH and DCACHE_OP_COMPARE are properly set by ->lookup. Fix by explicitly rejecting superblocks that allow case-insensitive dentries. Yes, this will be solved when we move d_op configuration back to ->s_d_op. Yet, we better have an explicit fix to avoid messing up again. While there, re-sort the entries to have more descriptive error messages first. Fixes: bb9cd9106b22 ("fscrypt: Have filesystems handle their d_ops") Acked-by: Amir Goldstein Reviewed-by: Eric Biggers Link: https://lore.kernel.org/r/20240221171412.10710-2-krisman@suse.de Signed-off-by: Gabriel Krisman Bertazi --- include/linux/fs.h | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'include/linux/fs.h') diff --git a/include/linux/fs.h b/include/linux/fs.h index e6ba0cc6f2ee..a0eb8b5759a6 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -3282,6 +3282,15 @@ extern int generic_check_addressable(unsigned, u64); extern void generic_set_encrypted_ci_d_ops(struct dentry *dentry); +static inline bool sb_has_encoding(const struct super_block *sb) +{ +#if IS_ENABLED(CONFIG_UNICODE) + return !!sb->s_encoding; +#else + return false; +#endif +} + int may_setattr(struct mnt_idmap *idmap, struct inode *inode, unsigned int ia_valid); int setattr_prepare(struct mnt_idmap *, struct dentry *, struct iattr *); -- cgit v1.2.3