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Message-ID: <20240127001013.2845-2-krisman@suse.de> Date: Fri, 26 Jan 2024 21:10:01 -0300 From: Gabriel Krisman Bertazi <krisman@...e.de> To: ebiggers@...nel.org, viro@...iv.linux.org.uk, jaegeuk@...nel.org, tytso@....edu Cc: amir73il@...il.com, linux-ext4@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net, linux-fsdevel@...r.kernel.org, Gabriel Krisman Bertazi <krisman@...e.de> Subject: [PATCH v4 01/12] ovl: 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. While there, re-sort the entries to have more descriptive error messages first. Fixes: bb9cd9106b22 ("fscrypt: Have filesystems handle their d_ops") Signed-off-by: Gabriel Krisman Bertazi <krisman@...e.de> Acked-by: Amir Goldstein <amir73il@...il.com> --- changes since v3: - Case insensitive filesystem ->Case insensitive capable filesystem (eric) - clarify patch summary line changes since v2: - Re-sort checks to trigger more descriptive error messages first (Amir) - Add code comment (Amir) --- fs/overlayfs/params.c | 14 +++++++++++--- include/linux/fs.h | 9 +++++++++ 2 files changed, 20 insertions(+), 3 deletions(-) diff --git a/fs/overlayfs/params.c b/fs/overlayfs/params.c index 3fe2dde1598f..488f920f79d2 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 diff --git a/include/linux/fs.h b/include/linux/fs.h index 98b7a7a8c42e..e6667ece5e64 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -3203,6 +3203,15 @@ 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 *); -- 2.43.0
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