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Subject[PATCH 4.4 006/118] fscrypto: require write access to mount to set encryption policy
Date
4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Biggers <ebiggers@google.com>

commit ba63f23d69a3a10e7e527a02702023da68ef8a6d upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/ext4/ioctl.c | 6 ++++++
1 file changed, 6 insertions(+)

--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -629,7 +629,13 @@ resizefs_out:
goto encryption_policy_out;
}

+ err = mnt_want_write_file(filp);
+ if (err)
+ goto encryption_policy_out;
+
err = ext4_process_policy(&policy, inode);
+
+ mnt_drop_write_file(filp);
encryption_policy_out:
return err;
#else

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