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f2fs: don't use casefolded comparison for "." and ".."

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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: 7ad08a58bf ("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>
This commit is contained in:
Eric Biggers 2022-05-14 10:59:29 -07:00 committed by Jaegeuk Kim
parent c81d5bae40
commit b5639bb431
3 changed files with 13 additions and 11 deletions
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3
fs/f2fs/dir.c
View File

@ -82,7 +82,8 @@ int f2fs_init_casefolded_name(const struct inode *dir,
#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)

10
fs/f2fs/f2fs.h
View File

@ -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

11
fs/f2fs/hash.c
View File

@ -91,7 +91,7 @@ static u32 TEA_hash_name(const u8 *p, size_t len)
/*
* 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 inode *dir, struct f2fs_filename *fname)
/*
* 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) {