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| author |   Gabriel Krisman Bertazi <krisman@suse.de> | 2024-02-21 12:14:03 -0500 |
|---|---|---|
| committer | Gabriel Krisman Bertazi <krisman@suse.de> | 2024-02-27 16:55:34 -0500 |
| commit | 2824083db76cb9d4b7910607b367e93b02912865 (patch) | |
| tree | fd26e1664e0ab9123ddce62ffc27220445c88281 /fs/overlayfs | |
| parent | libfs: Attempt exact-match comparison first during casefolded lookup (diff) | |
| download | wireguard-linux-2824083db76cb9d4b7910607b367e93b02912865.tar.xz wireguard-linux-2824083db76cb9d4b7910607b367e93b02912865.zip | |
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 <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>
Diffstat (limited to 'fs/overlayfs')
| -rw-r--r-- | fs/overlayfs/params.c | 14 |
1 files changed, 11 insertions, 3 deletions
diff --git a/fs/overlayfs/params.c b/fs/overlayfs/params.c index 112b4b12f825..36dcc530ac28 100644 --- a/fs/overlayfs/params.c +++ b/fs/overlayfs/params.c @@ -280,12 +280,20 @@ static int ovl_mount_dir_check(struct fs_context *fc, const struct path *path, { struct ovl_fs_context *ctx = fc->fs_private; - if (ovl_dentry_weird(path->dentry)) - return invalfc(fc, "filesystem on %s not supported", name); - if (!d_is_dir(path->dentry)) return invalfc(fc, "%s is not a directory", name); + /* + * Root dentries of case-insensitive capable filesystems might + * not have the dentry operations set, but still be incompatible + * with overlayfs. Check explicitly to prevent post-mount + * failures. + */ + if (sb_has_encoding(path->mnt->mnt_sb)) + return invalfc(fc, "case-insensitive capable filesystem on %s not supported", name); + + if (ovl_dentry_weird(path->dentry)) + return invalfc(fc, "filesystem on %s not supported", name); /* * Check whether upper path is read-only here to report failures |