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eCryptfs: NULL crypt_stat dereference during lookup
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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>
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@torvalds
Tyler Hicks authored and torvalds committed Mar 22, 2009
1 parent 8faece5 commit 2aac0cf
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Showing 3 changed files with 18 additions and 25 deletions.
10 changes: 6 additions & 4 deletions fs/ecryptfs/crypto.c
View file
Expand Up @@ -2221,17 +2221,19 @@ 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;

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1 change: 0 additions & 1 deletion fs/ecryptfs/ecryptfs_kernel.h
View file
Expand Up @@ -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,
Expand Down
32 changes: 12 additions & 20 deletions fs/ecryptfs/inode.c
View file
Expand Up @@ -246,14 +246,14 @@ ecryptfs_create(struct inode *directory_inode, struct dentry *ecryptfs_dentry,
*/
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)
{
struct dentry *lower_dir_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;
Expand Down Expand Up @@ -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) {
Expand Down Expand Up @@ -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;

Expand All @@ -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 "
Expand All @@ -426,7 +418,7 @@ static struct dentry *ecryptfs_lookup(struct inode *ecryptfs_dir_inode,
}
lookup_and_interpose:
rc = ecryptfs_lookup_and_interpose_lower(ecryptfs_dentry, lower_dentry,
crypt_stat, ecryptfs_dir_inode,
ecryptfs_dir_inode,
ecryptfs_nd);
goto out;
out_d_drop:
Expand Down

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