fscrypto: move ioctl processing more fully into common code

Multiple bugs were recently fixed in the "set encryption policy" ioctl.
To make it clear that fscrypt_process_policy() and fscrypt_get_policy()
implement ioctls and therefore their implementations must take standard
security and correctness precautions, rename them to
fscrypt_ioctl_set_policy() and fscrypt_ioctl_get_policy().  Make the
latter take in a struct file * to make it consistent with the former.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/crypto/policy.c

@@ -93,16 +93,19 @@ 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 file *filp,
-				const struct fscrypt_policy *policy)
+int fscrypt_ioctl_set_policy(struct file *filp, const void __user *arg)
 {
+	struct fscrypt_policy policy;
 	struct inode *inode = file_inode(filp);
 	int ret;
 
+	if (copy_from_user(&policy, arg, sizeof(policy)))
+		return -EFAULT;
+
 	if (!inode_owner_or_capable(inode))
 		return -EACCES;
 
-	if (policy->version != 0)
+	if (policy.version != 0)
 		return -EINVAL;
 
 	ret = mnt_want_write_file(filp);
@@ -120,9 +123,9 @@ int fscrypt_process_policy(struct file *filp,
 			ret = -ENOTEMPTY;
 		else
 			ret = create_encryption_context_from_policy(inode,
-								    policy);
+								    &policy);
 	} else if (!is_encryption_context_consistent_with_policy(inode,
-								 policy)) {
+								 &policy)) {
 		printk(KERN_WARNING
 		       "%s: Policy inconsistent with encryption context\n",
 		       __func__);
@@ -134,11 +137,13 @@ int fscrypt_process_policy(struct file *filp,
 	mnt_drop_write_file(filp);
 	return ret;
 }
-EXPORT_SYMBOL(fscrypt_process_policy);
+EXPORT_SYMBOL(fscrypt_ioctl_set_policy);
 
-int fscrypt_get_policy(struct inode *inode, struct fscrypt_policy *policy)
+int fscrypt_ioctl_get_policy(struct file *filp, void __user *arg)
 {
+	struct inode *inode = file_inode(filp);
 	struct fscrypt_context ctx;
+	struct fscrypt_policy policy;
 	int res;
 
 	if (!inode->i_sb->s_cop->get_context ||
@@ -151,15 +156,18 @@ int fscrypt_get_policy(struct inode *inode, struct fscrypt_policy *policy)
 	if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1)
 		return -EINVAL;
 
-	policy->version = 0;
-	policy->contents_encryption_mode = ctx.contents_encryption_mode;
-	policy->filenames_encryption_mode = ctx.filenames_encryption_mode;
-	policy->flags = ctx.flags;
-	memcpy(&policy->master_key_descriptor, ctx.master_key_descriptor,
+	policy.version = 0;
+	policy.contents_encryption_mode = ctx.contents_encryption_mode;
+	policy.filenames_encryption_mode = ctx.filenames_encryption_mode;
+	policy.flags = ctx.flags;
+	memcpy(policy.master_key_descriptor, ctx.master_key_descriptor,
 				FS_KEY_DESCRIPTOR_SIZE);
+
+	if (copy_to_user(arg, &policy, sizeof(policy)))
+		return -EFAULT;
 	return 0;
 }
-EXPORT_SYMBOL(fscrypt_get_policy);
+EXPORT_SYMBOL(fscrypt_ioctl_get_policy);
 
 int fscrypt_has_permitted_context(struct inode *parent, struct inode *child)
 {

fs/ext4/ext4.h

@@ -2338,8 +2338,8 @@ static inline void ext4_fname_free_filename(struct ext4_filename *fname) { }
 #define fscrypt_pullback_bio_page	fscrypt_notsupp_pullback_bio_page
 #define fscrypt_restore_control_page	fscrypt_notsupp_restore_control_page
 #define fscrypt_zeroout_range		fscrypt_notsupp_zeroout_range
-#define fscrypt_process_policy		fscrypt_notsupp_process_policy
-#define fscrypt_get_policy		fscrypt_notsupp_get_policy
+#define fscrypt_ioctl_set_policy	fscrypt_notsupp_ioctl_set_policy
+#define fscrypt_ioctl_get_policy	fscrypt_notsupp_ioctl_get_policy
 #define fscrypt_has_permitted_context	fscrypt_notsupp_has_permitted_context
 #define fscrypt_inherit_context		fscrypt_notsupp_inherit_context
 #define fscrypt_get_encryption_info	fscrypt_notsupp_get_encryption_info

fs/ext4/ioctl.c

@@ -765,22 +765,12 @@ long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 	}
 	case EXT4_IOC_PRECACHE_EXTENTS:
 		return ext4_ext_precache(inode);
-	case EXT4_IOC_SET_ENCRYPTION_POLICY: {
-#ifdef CONFIG_EXT4_FS_ENCRYPTION
-		struct fscrypt_policy policy;
 
+	case EXT4_IOC_SET_ENCRYPTION_POLICY:
 		if (!ext4_has_feature_encrypt(sb))
 			return -EOPNOTSUPP;
+		return fscrypt_ioctl_set_policy(filp, (const void __user *)arg);
 
-		if (copy_from_user(&policy,
-				   (struct fscrypt_policy __user *)arg,
-				   sizeof(policy)))
-			return -EFAULT;
-		return fscrypt_process_policy(filp, &policy);
-#else
-		return -EOPNOTSUPP;
-#endif
-	}
 	case EXT4_IOC_GET_ENCRYPTION_PWSALT: {
 		int err, err2;
 		struct ext4_sb_info *sbi = EXT4_SB(sb);
@@ -817,23 +807,9 @@ long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 			return -EFAULT;
 		return 0;
 	}
-	case EXT4_IOC_GET_ENCRYPTION_POLICY: {
-#ifdef CONFIG_EXT4_FS_ENCRYPTION
-		struct fscrypt_policy policy;
-		int err = 0;
-
-		if (!ext4_encrypted_inode(inode))
-			return -ENOENT;
-		err = fscrypt_get_policy(inode, &policy);
-		if (err)
-			return err;
-		if (copy_to_user((void __user *)arg, &policy, sizeof(policy)))
-			return -EFAULT;
-		return 0;
-#else
-		return -EOPNOTSUPP;
-#endif
-	}
+	case EXT4_IOC_GET_ENCRYPTION_POLICY:
+		return fscrypt_ioctl_get_policy(filp, (void __user *)arg);
+
 	case EXT4_IOC_FSGETXATTR:
 	{
 		struct fsxattr fa;

fs/f2fs/f2fs.h

@@ -2453,8 +2453,8 @@ static inline bool f2fs_may_encrypt(struct inode *inode)
 #define fscrypt_pullback_bio_page	fscrypt_notsupp_pullback_bio_page
 #define fscrypt_restore_control_page	fscrypt_notsupp_restore_control_page
 #define fscrypt_zeroout_range		fscrypt_notsupp_zeroout_range
-#define fscrypt_process_policy		fscrypt_notsupp_process_policy
-#define fscrypt_get_policy		fscrypt_notsupp_get_policy
+#define fscrypt_ioctl_set_policy	fscrypt_notsupp_ioctl_set_policy
+#define fscrypt_ioctl_get_policy	fscrypt_notsupp_ioctl_get_policy
 #define fscrypt_has_permitted_context	fscrypt_notsupp_has_permitted_context
 #define fscrypt_inherit_context		fscrypt_notsupp_inherit_context
 #define fscrypt_get_encryption_info	fscrypt_notsupp_get_encryption_info

fs/f2fs/file.c

@@ -1752,31 +1752,16 @@ static bool uuid_is_nonzero(__u8 u[16])
 
 static int f2fs_ioc_set_encryption_policy(struct file *filp, unsigned long arg)
 {
-	struct fscrypt_policy policy;
 	struct inode *inode = file_inode(filp);
 
-	if (copy_from_user(&policy, (struct fscrypt_policy __user *)arg,
-							sizeof(policy)))
-		return -EFAULT;
-
 	f2fs_update_time(F2FS_I_SB(inode), REQ_TIME);
 
-	return fscrypt_process_policy(filp, &policy);
+	return fscrypt_ioctl_set_policy(filp, (const void __user *)arg);
 }
 
 static int f2fs_ioc_get_encryption_policy(struct file *filp, unsigned long arg)
 {
-	struct fscrypt_policy policy;
-	struct inode *inode = file_inode(filp);
-	int err;
-
-	err = fscrypt_get_policy(inode, &policy);
-	if (err)
-		return err;
-
-	if (copy_to_user((struct fscrypt_policy __user *)arg, &policy, sizeof(policy)))
-		return -EFAULT;
-	return 0;
+	return fscrypt_ioctl_get_policy(filp, (void __user *)arg);
 }
 
 static int f2fs_ioc_get_encryption_pwsalt(struct file *filp, unsigned long arg)

include/linux/fscrypto.h

@@ -259,8 +259,8 @@ extern void fscrypt_restore_control_page(struct page *);
 extern int fscrypt_zeroout_range(const struct inode *, pgoff_t, sector_t,
 						unsigned int);
 /* policy.c */
-extern int fscrypt_process_policy(struct file *, const struct fscrypt_policy *);
-extern int fscrypt_get_policy(struct inode *, struct fscrypt_policy *);
+extern int fscrypt_ioctl_set_policy(struct file *, const void __user *);
+extern int fscrypt_ioctl_get_policy(struct file *, void __user *);
 extern int fscrypt_has_permitted_context(struct inode *, struct inode *);
 extern int fscrypt_inherit_context(struct inode *, struct inode *,
 					void *, bool);
@@ -334,14 +334,14 @@ static inline int fscrypt_notsupp_zeroout_range(const struct inode *i, pgoff_t p
 }
 
 /* policy.c */
-static inline int fscrypt_notsupp_process_policy(struct file *f,
-				const struct fscrypt_policy *p)
+static inline int fscrypt_notsupp_ioctl_set_policy(struct file *f,
+				const void __user *arg)
 {
 	return -EOPNOTSUPP;
 }
 
-static inline int fscrypt_notsupp_get_policy(struct inode *i,
-				struct fscrypt_policy *p)
+static inline int fscrypt_notsupp_ioctl_get_policy(struct file *f,
+				void __user *arg)
 {
 	return -EOPNOTSUPP;
 }