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authorEric Biggers <ebiggers@google.com>2019-03-20 11:39:10 -0700
committerTheodore Ts'o <tytso@mit.edu>2019-04-17 09:51:20 -0400
commit968dd6d0c6d6b6a989c6ddb9e2584a031b83e7b5 (patch)
tree747e028b00d4453e8de1b8959b739517e025efb0
parent6cc248684d3d23bbd073ae2fa73d3416c0558909 (diff)
downloadlinux-968dd6d0c6d6b6a989c6ddb9e2584a031b83e7b5.tar.bz2
fscrypt: fix race allowing rename() and link() of ciphertext dentries
Close some race conditions where fscrypt allowed rename() and link() on ciphertext dentries that had been looked up just prior to the key being concurrently added. It's better to return -ENOKEY in this case. This avoids doing the nonsensical thing of encrypting the names a second time when searching for the actual on-disk dir entries. It also guarantees that DCACHE_ENCRYPTED_NAME dentries are never rename()d, so the dcache won't have support all possible combinations of moving DCACHE_ENCRYPTED_NAME around during __d_move(). Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
-rw-r--r--fs/crypto/hooks.c12
-rw-r--r--include/linux/fscrypt.h9
2 files changed, 16 insertions, 5 deletions
diff --git a/fs/crypto/hooks.c b/fs/crypto/hooks.c
index a9492f75bbe1..2e7498a821a4 100644
--- a/fs/crypto/hooks.c
+++ b/fs/crypto/hooks.c
@@ -49,7 +49,8 @@ int fscrypt_file_open(struct inode *inode, struct file *filp)
}
EXPORT_SYMBOL_GPL(fscrypt_file_open);
-int __fscrypt_prepare_link(struct inode *inode, struct inode *dir)
+int __fscrypt_prepare_link(struct inode *inode, struct inode *dir,
+ struct dentry *dentry)
{
int err;
@@ -57,6 +58,10 @@ int __fscrypt_prepare_link(struct inode *inode, struct inode *dir)
if (err)
return err;
+ /* ... in case we looked up ciphertext name before key was added */
+ if (dentry->d_flags & DCACHE_ENCRYPTED_NAME)
+ return -ENOKEY;
+
if (!fscrypt_has_permitted_context(dir, inode))
return -EXDEV;
@@ -78,6 +83,11 @@ int __fscrypt_prepare_rename(struct inode *old_dir, struct dentry *old_dentry,
if (err)
return err;
+ /* ... in case we looked up ciphertext name(s) before key was added */
+ if ((old_dentry->d_flags | new_dentry->d_flags) &
+ DCACHE_ENCRYPTED_NAME)
+ return -ENOKEY;
+
if (old_dir != new_dir) {
if (IS_ENCRYPTED(new_dir) &&
!fscrypt_has_permitted_context(new_dir,
diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
index 09e368a515d1..855f743c226e 100644
--- a/include/linux/fscrypt.h
+++ b/include/linux/fscrypt.h
@@ -215,7 +215,8 @@ extern int fscrypt_zeroout_range(const struct inode *, pgoff_t, sector_t,
/* hooks.c */
extern int fscrypt_file_open(struct inode *inode, struct file *filp);
-extern int __fscrypt_prepare_link(struct inode *inode, struct inode *dir);
+extern int __fscrypt_prepare_link(struct inode *inode, struct inode *dir,
+ struct dentry *dentry);
extern int __fscrypt_prepare_rename(struct inode *old_dir,
struct dentry *old_dentry,
struct inode *new_dir,
@@ -401,8 +402,8 @@ static inline int fscrypt_file_open(struct inode *inode, struct file *filp)
return 0;
}
-static inline int __fscrypt_prepare_link(struct inode *inode,
- struct inode *dir)
+static inline int __fscrypt_prepare_link(struct inode *inode, struct inode *dir,
+ struct dentry *dentry)
{
return -EOPNOTSUPP;
}
@@ -497,7 +498,7 @@ static inline int fscrypt_prepare_link(struct dentry *old_dentry,
struct dentry *dentry)
{
if (IS_ENCRYPTED(dir))
- return __fscrypt_prepare_link(d_inode(old_dentry), dir);
+ return __fscrypt_prepare_link(d_inode(old_dentry), dir, dentry);
return 0;
}