[PATCH 5.18 714/879] f2fs: dont use casefolded comparison for "." and ".."

Greg Kroah-Hartman
2022-06-08T01:08:53Z

From: Eric Biggers <ebiggers@google.com>

commit b5639bb4313b9d455fc9fc4768d23a5e4ca8cb9d upstream.

Tryng to rename a directory that has all following properties fails with
EINVAL and triggers the 'WARN_ON_ONCE(!fscrypt_has_encryption_key(dir))'
in f2fs_match_ci_name():

- The directory is casefolded
- The directory is encrypted
- The directory's encryption key is not yet set up
- The parent directory is *not* encrypted

The problem is incorrect handling of the lookup of ".." to get the
parent reference to update. fscrypt_setup_filename() treats ".." (and
".") specially, as it's never encrypted. It's passed through as-is, and
setting up the directory's key is not attempted. As the name isn't a
no-key name, f2fs treats it as a "normal" name and attempts a casefolded
comparison. That breaks the assumption of the WARN_ON_ONCE() in
f2fs_match_ci_name() which assumes that for encrypted directories,
casefolded comparisons only happen when the directory's key is set up.

We could just remove this WARN_ON_ONCE(). However, since casefolding is
always a no-op on "." and ".." anyway, let's instead just not casefold
these names. This results in the standard bytewise comparison.

Fixes: 7ad08a58bf67 ("f2fs: Handle casefolding with Encryption")
Cc: <stable@vger.kernel.org> # v5.11+
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/f2fs/dir.c | 3 ++-
fs/f2fs/f2fs.h | 10 +++++-----
fs/f2fs/hash.c | 11 ++++++-----
3 files changed, 13 insertions(+), 11 deletions(-)

--- a/fs/f2fs/dir.c
+++ b/fs/f2fs/dir.c
@@ -82,7 +82,8 @@ int f2fs_init_casefolded_name(const stru
#if IS_ENABLED(CONFIG_UNICODE)
struct super_block *sb = dir->i_sb;

- if (IS_CASEFOLDED(dir)) {
+ if (IS_CASEFOLDED(dir) &&
+ !is_dot_dotdot(fname->usr_fname->name, fname->usr_fname->len)) {
fname->cf_name.name = f2fs_kmem_cache_alloc(f2fs_cf_name_slab,
GFP_NOFS, false, F2FS_SB(sb));
if (!fname->cf_name.name)
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -508,11 +508,11 @@ struct f2fs_filename {
#if IS_ENABLED(CONFIG_UNICODE)
/*
* For casefolded directories: the casefolded name, but it's left NULL
- * if the original name is not valid Unicode, if the directory is both
- * casefolded and encrypted and its encryption key is unavailable, or if
- * the filesystem is doing an internal operation where usr_fname is also
- * NULL. In all these cases we fall back to treating the name as an
- * opaque byte sequence.
+ * if the original name is not valid Unicode, if the original name is
+ * "." or "..", if the directory is both casefolded and encrypted and
+ * its encryption key is unavailable, or if the filesystem is doing an
+ * internal operation where usr_fname is also NULL. In all these cases
+ * we fall back to treating the name as an opaque byte sequence.
*/
struct fscrypt_str cf_name;
#endif
--- a/fs/f2fs/hash.c
+++ b/fs/f2fs/hash.c
@@ -91,7 +91,7 @@ static u32 TEA_hash_name(const u8 *p, si
/*
* Compute @fname->hash. For all directories, @fname->disk_name must be set.
* For casefolded directories, @fname->usr_fname must be set, and also
- * @fname->cf_name if the filename is valid Unicode.
+ * @fname->cf_name if the filename is valid Unicode and is not "." or "..".
*/
void f2fs_hash_filename(const struct inode *dir, struct f2fs_filename *fname)
{
@@ -110,10 +110,11 @@ void f2fs_hash_filename(const struct ino
/*
* If the casefolded name is provided, hash it instead of the
* on-disk name. If the casefolded name is *not* provided, that
- * should only be because the name wasn't valid Unicode, so fall
- * back to treating the name as an opaque byte sequence. Note
- * that to handle encrypted directories, the fallback must use
- * usr_fname (plaintext) rather than disk_name (ciphertext).
+ * should only be because the name wasn't valid Unicode or was
+ * "." or "..", so fall back to treating the name as an opaque
+ * byte sequence. Note that to handle encrypted directories,
+ * the fallback must use usr_fname (plaintext) rather than
+ * disk_name (ciphertext).
*/
WARN_ON_ONCE(!fname->usr_fname->name);
if (fname->cf_name.name) {