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fs, fscrypt: clear DCACHE_ENCRYPTED_NAME when unaliasing directory 

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>
This commit is contained in:
Eric Biggers 2019-03-20 11:39:11 -07:00 committed by Theodore Ts'o
parent 968dd6d0c6
commit 0bf3d5c160
2 changed files with 18 additions and 0 deletions
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2
fs/dcache.c
View File

@ -18,6 +18,7 @@
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/fscrypt.h>
#include <linux/fsnotify.h>
#include <linux/slab.h>
#include <linux/init.h>
@ -2795,6 +2796,7 @@ 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);

16
include/linux/fscrypt.h
View File

@ -89,6 +89,18 @@ static inline bool fscrypt_dummy_context_enabled(struct inode *inode)
inode->i_sb->s_cop->dummy_context(inode);
}
/*
* 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)
{
dentry->d_flags &= ~DCACHE_ENCRYPTED_NAME;
}
/* crypto.c */
extern void fscrypt_enqueue_decrypt_work(struct work_struct *);
extern struct fscrypt_ctx *fscrypt_get_ctx(gfp_t);
@ -244,6 +256,10 @@ static inline bool fscrypt_dummy_context_enabled(struct inode *inode)
return false;
}
static inline void fscrypt_handle_d_move(struct dentry *dentry)
{
}
/* crypto.c */
static inline void fscrypt_enqueue_decrypt_work(struct work_struct *work)
{