From ba63f23d69a3a10e7e527a02702023da68ef8a6d Mon Sep 17 00:00:00 2001
From: Eric Biggers <ebiggers@google.com>
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 <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>
---
 include/linux/fscrypto.h | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

(limited to 'include')

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;
-- 
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