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From: Eric Biggers <ebiggers@kernel.org>
To: linux-fscrypt@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
	linux-f2fs-devel@lists.sourceforge.net,
	linux-mtd@lists.infradead.org, linux-unionfs@vger.kernel.org,
	Sarthak Kukreti <sarthakkukreti@chromium.org>,
	Gao Xiang <gaoxiang25@huawei.com>
Subject: [PATCH v2 2/5] fscrypt: fix race allowing rename() and link() of ciphertext dentries
Date: Wed, 20 Mar 2019 11:39:10 -0700	[thread overview]
Message-ID: <20190320183913.12686-3-ebiggers@kernel.org> (raw)
In-Reply-To: <20190320183913.12686-1-ebiggers@kernel.org>

From: Eric Biggers <ebiggers@google.com>

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>
---
 fs/crypto/hooks.c       | 12 +++++++++++-
 include/linux/fscrypt.h |  9 +++++----
 2 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/fs/crypto/hooks.c b/fs/crypto/hooks.c
index a9492f75bbe13..2e7498a821a48 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 5a0c3fee1ea2b..4ad7a856e0f1c 100644
--- a/include/linux/fscrypt.h
+++ b/include/linux/fscrypt.h
@@ -214,7 +214,8 @@ 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;
 }
 
-- 
2.21.0.225.g810b269d1ac-goog


  parent reply	other threads:[~2019-03-20 18:40 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-20 18:39 [PATCH v2 0/5] fscrypt: d_revalidate fixes and cleanups Eric Biggers
2019-03-20 18:39 ` [PATCH v2 1/5] fscrypt: clean up and improve dentry revalidation Eric Biggers
2019-04-16 23:08   ` Theodore Ts'o
2019-04-17  0:10     ` Eric Biggers
2019-04-17 13:50       ` Theodore Ts'o
2019-03-20 18:39 ` Eric Biggers [this message]
2019-04-17 13:53   ` [PATCH v2 2/5] fscrypt: fix race allowing rename() and link() of ciphertext dentries Theodore Ts'o
2019-03-20 18:39 ` [PATCH v2 3/5] fs, fscrypt: clear DCACHE_ENCRYPTED_NAME when unaliasing directory Eric Biggers
2019-04-17 14:06   ` Theodore Ts'o
2019-03-20 18:39 ` [PATCH v2 4/5] fscrypt: only set dentry_operations on ciphertext dentries Eric Biggers
2019-04-17 14:07   ` Theodore Ts'o
2019-03-20 18:39 ` [PATCH v2 5/5] fscrypt: fix race where ->lookup() marks plaintext dentry as ciphertext Eric Biggers
2019-04-17 14:24   ` Theodore Ts'o
2019-04-01 17:11 ` [PATCH v2 0/5] fscrypt: d_revalidate fixes and cleanups Eric Biggers
2019-04-08  8:22   ` Richard Weinberger

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