Re: [PATCH] eCryptfs: NULL crypt_stat dereference during lookup
From: Dustin Kirkland
Date: Fri Mar 20 2009 - 18:43:21 EST
On Fri, Mar 20, 2009 at 2:23 AM, Tyler Hicks <tyhicks@xxxxxxxxxxxxxxxxxx> wrote:
> 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@xxxxxxxxxxxxxxxxxx>
Acked-by: Dustin Kirkland <kirkland@xxxxxxxxxxxxx>
> ---
> 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 75bee99..8b65f28 100644
> --- a/fs/ecryptfs/crypto.c
> +++ b/fs/ecryptfs/crypto.c
> @@ -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;
>
> diff --git a/fs/ecryptfs/ecryptfs_kernel.h b/fs/ecryptfs/ecryptfs_kernel.h
> index eb2267e..ac749d4 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 5697899..55b3145 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_dentry, lower_dentry,
> - crypt_stat, ecryptfs_dir_inode,
> + ecryptfs_dir_inode,
> ecryptfs_nd);
> goto out;
> out_d_drop:
> --
> 1.5.3.7
>
>
--
:-Dustin
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