From ba63f23d69a3a10e7e527a02702023da68ef8a6d Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Thu, 8 Sep 2016 14:20:38 -0700 Subject: fscrypto: require write access to mount to set encryption policy Since setting an encryption policy requires writing metadata to the filesystem, it should be guarded by mnt_want_write/mnt_drop_write. Otherwise, a user could cause a write to a frozen or readonly filesystem. This was handled correctly by f2fs but not by ext4. Make fscrypt_process_policy() handle it rather than relying on the filesystem to get it right. Signed-off-by: Eric Biggers Cc: stable@vger.kernel.org # 4.1+; check fs/{ext4,f2fs} Signed-off-by: Theodore Ts'o Acked-by: Jaegeuk Kim --- fs/crypto/policy.c | 38 +++++++++++++++++++++++++------------- fs/ext4/ioctl.c | 2 +- fs/f2fs/file.c | 9 +-------- include/linux/fscrypto.h | 5 ++--- 4 files changed, 29 insertions(+), 25 deletions(-) diff --git a/fs/crypto/policy.c b/fs/crypto/policy.c index f96547f83cab..ed115acb5dee 100644 --- a/fs/crypto/policy.c +++ b/fs/crypto/policy.c @@ -11,6 +11,7 @@ #include #include #include +#include static int inode_has_encryption_context(struct inode *inode) { @@ -92,31 +93,42 @@ static int create_encryption_context_from_policy(struct inode *inode, return inode->i_sb->s_cop->set_context(inode, &ctx, sizeof(ctx), NULL); } -int fscrypt_process_policy(struct inode *inode, +int fscrypt_process_policy(struct file *filp, const struct fscrypt_policy *policy) { + struct inode *inode = file_inode(filp); + int ret; + if (!inode_owner_or_capable(inode)) return -EACCES; if (policy->version != 0) return -EINVAL; + ret = mnt_want_write_file(filp); + if (ret) + return ret; + if (!inode_has_encryption_context(inode)) { if (!S_ISDIR(inode->i_mode)) - return -EINVAL; - if (!inode->i_sb->s_cop->empty_dir) - return -EOPNOTSUPP; - if (!inode->i_sb->s_cop->empty_dir(inode)) - return -ENOTEMPTY; - return create_encryption_context_from_policy(inode, policy); + ret = -EINVAL; + else if (!inode->i_sb->s_cop->empty_dir) + ret = -EOPNOTSUPP; + else if (!inode->i_sb->s_cop->empty_dir(inode)) + ret = -ENOTEMPTY; + else + ret = create_encryption_context_from_policy(inode, + policy); + } else if (!is_encryption_context_consistent_with_policy(inode, + policy)) { + printk(KERN_WARNING + "%s: Policy inconsistent with encryption context\n", + __func__); + ret = -EINVAL; } - if (is_encryption_context_consistent_with_policy(inode, policy)) - return 0; - - printk(KERN_WARNING "%s: Policy inconsistent with encryption context\n", - __func__); - return -EINVAL; + mnt_drop_write_file(filp); + return ret; } EXPORT_SYMBOL(fscrypt_process_policy); diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c index 10686fd67fb4..1bb7df5e4536 100644 --- a/fs/ext4/ioctl.c +++ b/fs/ext4/ioctl.c @@ -776,7 +776,7 @@ resizefs_out: (struct fscrypt_policy __user *)arg, sizeof(policy))) return -EFAULT; - return fscrypt_process_policy(inode, &policy); + return fscrypt_process_policy(filp, &policy); #else return -EOPNOTSUPP; #endif diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c index 47abb96098e4..28f4f4cbb8d8 100644 --- a/fs/f2fs/file.c +++ b/fs/f2fs/file.c @@ -1757,21 +1757,14 @@ static int f2fs_ioc_set_encryption_policy(struct file *filp, unsigned long arg) { struct fscrypt_policy policy; struct inode *inode = file_inode(filp); - int ret; if (copy_from_user(&policy, (struct fscrypt_policy __user *)arg, sizeof(policy))) return -EFAULT; - ret = mnt_want_write_file(filp); - if (ret) - return ret; - f2fs_update_time(F2FS_I_SB(inode), REQ_TIME); - ret = fscrypt_process_policy(inode, &policy); - mnt_drop_write_file(filp); - return ret; + return fscrypt_process_policy(filp, &policy); } static int f2fs_ioc_get_encryption_policy(struct file *filp, unsigned long arg) diff --git a/include/linux/fscrypto.h b/include/linux/fscrypto.h index cfa6cde25f8e..76cff18bb032 100644 --- a/include/linux/fscrypto.h +++ b/include/linux/fscrypto.h @@ -274,8 +274,7 @@ extern void fscrypt_restore_control_page(struct page *); extern int fscrypt_zeroout_range(struct inode *, pgoff_t, sector_t, unsigned int); /* policy.c */ -extern int fscrypt_process_policy(struct inode *, - const struct fscrypt_policy *); +extern int fscrypt_process_policy(struct file *, const struct fscrypt_policy *); extern int fscrypt_get_policy(struct inode *, struct fscrypt_policy *); extern int fscrypt_has_permitted_context(struct inode *, struct inode *); extern int fscrypt_inherit_context(struct inode *, struct inode *, @@ -345,7 +344,7 @@ static inline int fscrypt_notsupp_zeroout_range(struct inode *i, pgoff_t p, } /* policy.c */ -static inline int fscrypt_notsupp_process_policy(struct inode *i, +static inline int fscrypt_notsupp_process_policy(struct file *f, const struct fscrypt_policy *p) { return -EOPNOTSUPP; -- cgit v1.2.3-58-ga151