fscrypto: add authorization check for setting encryption policy

commit 163ae1c6ad6299b19e22b4a35d5ab24a89791a98 upstream.

On an ext4 or f2fs filesystem with file encryption supported, a user
could set an encryption policy on any empty directory(*) to which they
had readonly access.  This is obviously problematic, since such a
directory might be owned by another user and the new encryption policy
would prevent that other user from creating files in their own directory
(for example).

Fix this by requiring inode_owner_or_capable() permission to set an
encryption policy.  This means that either the caller must own the file,
or the caller must have the capability CAP_FOWNER.

(*) Or also on any regular file, for f2fs v4.6 and later and ext4
    v4.8-rc1 and later; a separate bug fix is coming for that.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/ext4/crypto_policy.c b/fs/ext4/crypto_policy.c
index ad050698143fde483e9c5cddc5e32c88041a9b29..8a9feb341f314ea94f7f4e5984aea57f4b8e20a4 100644 (file)
--- a/fs/ext4/crypto_policy.c
+++ b/fs/ext4/crypto_policy.c
@@ -102,6 +102,9 @@ static int ext4_create_encryption_context_from_policy(
 int ext4_process_policy(const struct ext4_encryption_policy *policy,
                        struct inode *inode)
 {
+       if (!inode_owner_or_capable(inode))
+               return -EACCES;
+
        if (policy->version != 0)
                return -EINVAL;
 

diff --git a/fs/f2fs/crypto_policy.c b/fs/f2fs/crypto_policy.c
index d4a96af513c22f28ea1242496286d4ff1a606567..e504f548b64e3045177ae884b3352ac34bd7466e 100644 (file)
--- a/fs/f2fs/crypto_policy.c
+++ b/fs/f2fs/crypto_policy.c
@@ -89,6 +89,9 @@ static int f2fs_create_encryption_context_from_policy(
 int f2fs_process_policy(const struct f2fs_encryption_policy *policy,
                        struct inode *inode)
 {
+       if (!inode_owner_or_capable(inode))
+               return -EACCES;
+
        if (policy->version != 0)
                return -EINVAL;