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Gabriel Krisman Bertazi c6f95031cf ovl: Always reject mounting over case-insensitive directories

[ Upstream commit 2824083db76cb9d4b7910607b367e93b02912865 ]

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 <amir73il@gmail.com>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20240221171412.10710-2-krisman@suse.de
Signed-off-by: Gabriel Krisman Bertazi <krisman@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>

2024-03-26 18:19:18 -04:00

copy_up.c

v6.6-rc4.vfs.fixes

2023-09-26 08:50:30 -07:00

dir.c

ovl: store enum redirect_mode in config instead of a string

2023-06-19 14:02:01 +03:00

export.c

ovl: fix NULL pointer defer when encoding non-decodable lower fid

2023-10-03 09:24:11 +03:00

file.c

ovl: fix file reference leak when submitting aio