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FAILED: patch "[PATCH] fscrypto: require write access to mount to set encryption" failed to apply to 4.4-stable tree

PATCH [email protected] 1 participant 1 message Sep 12, 2016

Subsystems (4)
Stable branch ext4 file system F2FS file system fscrypt: file system level encryption support
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The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

Quoted 1 line

From ba63f23d69a3a10e7e527a02702023da68ef8a6d Mon Sep 17 00:00:00 2001

From: Eric Biggers <[email protected]>
Date: Thu, 8 Sep 2016 14:20:38 -0700
Subject: [PATCH] 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 <[email protected]>
Cc [email protected] # 4.1+; check fs/{ext4,f2fs}
Signed-off-by Theodore Ts'o <[email protected]>
Acked-by Jaegeuk Kim <[email protected]>
fs/crypto/policy.c +25 -13
index f96547f83cab..ed115acb5dee 100644
@@ -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);
fs/ext4/ioctl.c +1 -1
index 10686fd67fb4..1bb7df5e4536 100644
@@ -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
fs/f2fs/file.c +1 -8
index 47abb96098e4..28f4f4cbb8d8 100644
@@ -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)
include/linux/fscrypto.h +2 -3
index cfa6cde25f8e..76cff18bb032 100644
@@ -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;