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fs, fscrypt: clear DCACHE_ENCRYPTED_NAME when unaliasing directory

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commit 0bf3d5c1604ecbbd4e49e9f5b3c79152b87adb0d upstream.

Make __d_move() clear DCACHE_ENCRYPTED_NAME on the source dentry.  This
is needed for when d_splice_alias() moves a directory's encrypted alias
to its decrypted alias as a result of the encryption key being added.

Otherwise, the decrypted alias will incorrectly be invalidated on the
next lookup, causing problems such as unmounting a mount the user just
mount()ed there.

Note that we don't have to support arbitrary moves of this flag because
fscrypt doesn't allow dentries with DCACHE_ENCRYPTED_NAME to be the
source or target of a rename().

Fixes: 28b4c26396 ("ext4 crypto: revalidate dentry after adding or removing the key")
Reported-by: Sarthak Kukreti <sarthakkukreti@chromium.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Eric Biggers 2020-10-31 15:05:51 -07:00 committed by Greg Kroah-Hartman
parent 000d849574
commit 906242d10b
1 changed files with 15 additions and 0 deletions
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15
fs/dcache.c
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@ -2712,6 +2712,20 @@ static void copy_name(struct dentry *dentry, struct dentry *target)
call_rcu(&old_name->u.head, __d_free_external_name);
}
/*
* When d_splice_alias() moves a directory's encrypted alias to its decrypted
* alias as a result of the encryption key being added, DCACHE_ENCRYPTED_NAME
* must be cleared. Note that we don't have to support arbitrary moves of this
* flag because fscrypt doesn't allow encrypted aliases to be the source or
* target of a rename().
*/
static inline void fscrypt_handle_d_move(struct dentry *dentry)
{
#if IS_ENABLED(CONFIG_FS_ENCRYPTION)
dentry->d_flags &= ~DCACHE_ENCRYPTED_NAME;
#endif
}
/*
* __d_move - move a dentry
* @dentry: entry to move
@ -2787,6 +2801,7 @@ static void __d_move(struct dentry *dentry, struct dentry *target,
list_move(&dentry->d_child, &dentry->d_parent->d_subdirs);
__d_rehash(dentry);
fsnotify_update_flags(dentry);
fscrypt_handle_d_move(dentry);
write_seqcount_end(&target->d_seq);
write_seqcount_end(&dentry->d_seq);