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author | Eric Biggers <ebiggers@google.com> | 2016-09-08 14:20:38 -0700 |
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committer | Theodore Ts'o <tytso@mit.edu> | 2016-09-10 01:18:57 -0400 |
commit | ba63f23d69a3a10e7e527a02702023da68ef8a6d (patch) | |
tree | ef70ece0179f4d642e0b0b4d5f6aa6cfed7c9e74 /fs/crypto | |
parent | 002ced4be6429918800ce3e41d5cbc2d7c01822c (diff) | |
download | linux-stable-ba63f23d69a3a10e7e527a02702023da68ef8a6d.tar.gz linux-stable-ba63f23d69a3a10e7e527a02702023da68ef8a6d.tar.bz2 linux-stable-ba63f23d69a3a10e7e527a02702023da68ef8a6d.zip |
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 <ebiggers@google.com>
Cc: stable@vger.kernel.org # 4.1+; check fs/{ext4,f2fs}
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Acked-by: Jaegeuk Kim <jaegeuk@kernel.org>
Diffstat (limited to 'fs/crypto')
-rw-r--r-- | fs/crypto/policy.c | 38 |
1 files changed, 25 insertions, 13 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 <linux/random.h> #include <linux/string.h> #include <linux/fscrypto.h> +#include <linux/mount.h> 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); |