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Old 03-20-2009, 06:23 AM
Tyler Hicks
 
Default eCryptfs: NULL crypt_stat dereference during lookup

Bug: #345766

If ecryptfs_encrypted_view or ecryptfs_xattr_metadata were being
specified as mount options, a NULL pointer dereference of crypt_stat
was possible during lookup.

This patch moves the crypt_stat assignment into
ecryptfs_lookup_and_interpose_lower(), ensuring that crypt_stat
will not be NULL before we attempt to dereference it.

Thanks to Dan Carpenter and his static analysis tool, smatch, for
finding this bug.

Signed-off-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>
Acked-by: Dustin Kirkland <kirkland@canonical.com>
Cc: Dan Carpenter <error27@gmail.com>
Cc: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit 2aac0cf88681bfa092f731553bc7fbd23516be73)

Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
---
fs/ecryptfs/crypto.c | 10 ++++++----
fs/ecryptfs/ecryptfs_kernel.h | 1 -
fs/ecryptfs/inode.c | 32 ++++++++++++--------------------
3 files changed, 18 insertions(+), 25 deletions(-)

diff --git a/fs/ecryptfs/crypto.c b/fs/ecryptfs/crypto.c
index bdca1f4..1607e09 100644
--- a/fs/ecryptfs/crypto.c
+++ b/fs/ecryptfs/crypto.c
@@ -2208,17 +2208,19 @@ int ecryptfs_decode_and_decrypt_filename(char **plaintext_name,
struct dentry *ecryptfs_dir_dentry,
const char *name, size_t name_size)
{
+ struct ecryptfs_mount_crypt_stat *mount_crypt_stat =
+ &ecryptfs_superblock_to_private(
+ ecryptfs_dir_dentry->d_sb)->mount_crypt_stat;
char *decoded_name;
size_t decoded_name_size;
size_t packet_size;
int rc = 0;

- if ((name_size > ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE)
+ if ((mount_crypt_stat->flags & ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES)
+ && !(mount_crypt_stat->flags & ECRYPTFS_ENCRYPTED_VIEW_ENABLED)
+ && (name_size > ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE)
&& (strncmp(name, ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX,
ECRYPTFS_FNEK_ENCRYPTED_FILENAME_PREFIX_SIZE) == 0)) {
- struct ecryptfs_mount_crypt_stat *mount_crypt_stat =
- &ecryptfs_superblock_to_private(
- ecryptfs_dir_dentry->d_sb)->mount_crypt_stat;
const char *orig_name = name;
size_t orig_name_size = name_size;

diff --git a/fs/ecryptfs/ecryptfs_kernel.h b/fs/ecryptfs/ecryptfs_kernel.h
index fa6f1f4..1d0b5f8 100644
--- a/fs/ecryptfs/ecryptfs_kernel.h
+++ b/fs/ecryptfs/ecryptfs_kernel.h
@@ -620,7 +620,6 @@ int ecryptfs_interpose(struct dentry *hidden_dentry,
u32 flags);
int ecryptfs_lookup_and_interpose_lower(struct dentry *ecryptfs_dentry,
struct dentry *lower_dentry,
- struct ecryptfs_crypt_stat *crypt_stat,
struct inode *ecryptfs_dir_inode,
struct nameidata *ecryptfs_nd);
int ecryptfs_decode_and_decrypt_filename(char **decrypted_name,
diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index 17a96ec..82378fb 100644
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c
@@ -246,7 +246,6 @@ out:
*/
int ecryptfs_lookup_and_interpose_lower(struct dentry *ecryptfs_dentry,
struct dentry *lower_dentry,
- struct ecryptfs_crypt_stat *crypt_stat,
struct inode *ecryptfs_dir_inode,
struct nameidata *ecryptfs_nd)
{
@@ -254,6 +253,7 @@ int ecryptfs_lookup_and_interpose_lower(struct dentry *ecryptfs_dentry,
struct vfsmount *lower_mnt;
struct inode *lower_inode;
struct ecryptfs_mount_crypt_stat *mount_crypt_stat;
+ struct ecryptfs_crypt_stat *crypt_stat;
char *page_virt = NULL;
u64 file_size;
int rc = 0;
@@ -314,6 +314,11 @@ int ecryptfs_lookup_and_interpose_lower(struct dentry *ecryptfs_dentry,
goto out_free_kmem;
}
}
+ crypt_stat = &ecryptfs_inode_to_private(
+ ecryptfs_dentry->d_inode)->crypt_stat;
+ /* TODO: lock for crypt_stat comparison */
+ if (!(crypt_stat->flags & ECRYPTFS_POLICY_APPLIED))
+ ecryptfs_set_default_sizes(crypt_stat);
rc = ecryptfs_read_and_validate_header_region(page_virt ,
ecryptfs_dentry->d_inode);
if (rc) {
@@ -362,9 +367,7 @@ static struct dentry *ecryptfs_lookup(struct inode *ecryptfs_dir_inode,
{
char *encrypted_and_encoded_name = NULL;
size_t encrypted_and_encoded_name_size;
- struct ecryptfs_crypt_stat *crypt_stat = NULL;
struct ecryptfs_mount_crypt_stat *mount_crypt_stat = NULL;
- struct ecryptfs_inode_info *inode_info;
struct dentry *lower_dir_dentry, *lower_dentry;
int rc = 0;

@@ -388,26 +391,15 @@ static struct dentry *ecryptfs_lookup(struct inode *ecryptfs_dir_inode,
}
if (lower_dentry->d_inode)
goto lookup_and_interpose;
- inode_info = ecryptfs_inode_to_private(ecryptfs_dentry->d_inode);
- if (inode_info) {
- crypt_stat = &inode_info->crypt_stat;
- /* TODO: lock for crypt_stat comparison */
- if (!(crypt_stat->flags & ECRYPTFS_POLICY_APPLIED))
- ecryptfs_set_default_sizes(crypt_stat);
- }
- if (crypt_stat)
- mount_crypt_stat = crypt_stat->mount_crypt_stat;
- else
- mount_crypt_stat = &ecryptfs_superblock_to_private(
- ecryptfs_dentry->d_sb)->mount_crypt_stat;
- if (!(crypt_stat && (crypt_stat->flags & ECRYPTFS_ENCRYPT_FILENAMES))
- && !(mount_crypt_stat && (mount_crypt_stat->flags
- & ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES)))
+ mount_crypt_stat = &ecryptfs_superblock_to_private(
+ ecryptfs_dentry->d_sb)->mount_crypt_stat;
+ if (!(mount_crypt_stat
+ && (mount_crypt_stat->flags & ECRYPTFS_GLOBAL_ENCRYPT_FILENAMES)))
goto lookup_and_interpose;
dput(lower_dentry);
rc = ecryptfs_encrypt_and_encode_filename(
&encrypted_and_encoded_name, &encrypted_and_encoded_name_size,
- crypt_stat, mount_crypt_stat, ecryptfs_dentry->d_name.name,
+ NULL, mount_crypt_stat, ecryptfs_dentry->d_name.name,
ecryptfs_dentry->d_name.len);
if (rc) {
printk(KERN_ERR "%s: Error attempting to encrypt and encode "
@@ -426,7 +418,7 @@ static struct dentry *ecryptfs_lookup(struct inode *ecryptfs_dir_inode,
}
lookup_and_interpose:
rc = ecryptfs_lookup_and_interpose_lower(ecryptfs_dentr y, lower_dentry,
- crypt_stat, ecryptfs_dir_inode,
+ ecryptfs_dir_inode,
ecryptfs_nd);
goto out;
out_d_drop:
--
1.5.6.3


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