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authorGabriel Krisman Bertazi <krisman@suse.de>2024-02-21 20:14:03 +0300
committerGabriel Krisman Bertazi <krisman@suse.de>2024-02-28 00:55:34 +0300
commit2824083db76cb9d4b7910607b367e93b02912865 (patch)
treefd26e1664e0ab9123ddce62ffc27220445c88281 /fs/overlayfs
parent0906fbb2f7ad6ae4b1bee8777bf83171a12c10b0 (diff)
downloadlinux-2824083db76cb9d4b7910607b367e93b02912865.tar.xz
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.c14
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