fuse: allow umask processing in userspace

This patch lets filesystems handle masking the file mode on creation.
This is needed if filesystem is using ACLs.

 - The CREATE, MKDIR and MKNOD requests are extended with a "umask"
   parameter.

 - A new FUSE_DONT_MASK flag is added to the INIT request/reply.  With
   this the filesystem may request that the create mode is not masked.

CC: Jean-Pierre André <[email protected]>
Signed-off-by: Miklos Szeredi <[email protected]>

Author: Miklos Szeredi

fs/fuse/dir.c

@@ -375,7 +375,7 @@ static int fuse_create_open(struct inode *dir, struct dentry *entry, int mode,
 	struct fuse_conn *fc = get_fuse_conn(dir);
 	struct fuse_req *req;
 	struct fuse_req *forget_req;
-	struct fuse_open_in inarg;
+	struct fuse_create_in inarg;
 	struct fuse_open_out outopen;
 	struct fuse_entry_out outentry;
 	struct fuse_file *ff;
@@ -399,15 +399,20 @@ static int fuse_create_open(struct inode *dir, struct dentry *entry, int mode,
 	if (!ff)
 		goto out_put_request;
 
+	if (!fc->dont_mask)
+		mode &= ~current_umask();
+
 	flags &= ~O_NOCTTY;
 	memset(&inarg, 0, sizeof(inarg));
 	memset(&outentry, 0, sizeof(outentry));
 	inarg.flags = flags;
 	inarg.mode = mode;
+	inarg.umask = current_umask();
 	req->in.h.opcode = FUSE_CREATE;
 	req->in.h.nodeid = get_node_id(dir);
 	req->in.numargs = 2;
-	req->in.args[0].size = sizeof(inarg);
+	req->in.args[0].size = fc->minor < 12 ? sizeof(struct fuse_open_in) :
+						sizeof(inarg);
 	req->in.args[0].value = &inarg;
 	req->in.args[1].size = entry->d_name.len + 1;
 	req->in.args[1].value = entry->d_name.name;
@@ -546,12 +551,17 @@ static int fuse_mknod(struct inode *dir, struct dentry *entry, int mode,
 	if (IS_ERR(req))
 		return PTR_ERR(req);
 
+	if (!fc->dont_mask)
+		mode &= ~current_umask();
+
 	memset(&inarg, 0, sizeof(inarg));
 	inarg.mode = mode;
 	inarg.rdev = new_encode_dev(rdev);
+	inarg.umask = current_umask();
 	req->in.h.opcode = FUSE_MKNOD;
 	req->in.numargs = 2;
-	req->in.args[0].size = sizeof(inarg);
+	req->in.args[0].size = fc->minor < 12 ? FUSE_COMPAT_MKNOD_IN_SIZE :
+						sizeof(inarg);
 	req->in.args[0].value = &inarg;
 	req->in.args[1].size = entry->d_name.len + 1;
 	req->in.args[1].value = entry->d_name.name;
@@ -578,8 +588,12 @@ static int fuse_mkdir(struct inode *dir, struct dentry *entry, int mode)
 	if (IS_ERR(req))
 		return PTR_ERR(req);
 
+	if (!fc->dont_mask)
+		mode &= ~current_umask();
+
 	memset(&inarg, 0, sizeof(inarg));
 	inarg.mode = mode;
+	inarg.umask = current_umask();
 	req->in.h.opcode = FUSE_MKDIR;
 	req->in.numargs = 2;
 	req->in.args[0].size = sizeof(inarg);

fs/fuse/fuse_i.h

@@ -446,6 +446,9 @@ struct fuse_conn {
 	/** Do multi-page cached writes */
 	unsigned big_writes:1;
 
+	/** Don't apply umask to creation modes */
+	unsigned dont_mask:1;
+
 	/** The number of requests waiting for completion */
 	atomic_t num_waiting;
 

fs/fuse/inode.c

@@ -725,6 +725,8 @@ static void process_init_reply(struct fuse_conn *fc, struct fuse_req *req)
 			}
 			if (arg->flags & FUSE_BIG_WRITES)
 				fc->big_writes = 1;
+			if (arg->flags & FUSE_DONT_MASK)
+				fc->dont_mask = 1;
 		} else {
 			ra_pages = fc->max_read / PAGE_CACHE_SIZE;
 			fc->no_lock = 1;
@@ -748,7 +750,7 @@ static void fuse_send_init(struct fuse_conn *fc, struct fuse_req *req)
 	arg->minor = FUSE_KERNEL_MINOR_VERSION;
 	arg->max_readahead = fc->bdi.ra_pages * PAGE_CACHE_SIZE;
 	arg->flags |= FUSE_ASYNC_READ | FUSE_POSIX_LOCKS | FUSE_ATOMIC_O_TRUNC |
-		FUSE_EXPORT_SUPPORT | FUSE_BIG_WRITES;
+		FUSE_EXPORT_SUPPORT | FUSE_BIG_WRITES | FUSE_DONT_MASK;
 	req->in.h.opcode = FUSE_INIT;
 	req->in.numargs = 1;
 	req->in.args[0].size = sizeof(*arg);
@@ -864,6 +866,11 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)
 	if (err)
 		goto err_put_conn;
 
+	/* Handle umasking inside the fuse code */
+	if (sb->s_flags & MS_POSIXACL)
+		fc->dont_mask = 1;
+	sb->s_flags |= MS_POSIXACL;
+
 	fc->release = fuse_free_conn;
 	fc->flags = d.flags;
 	fc->user_id = d.user_id;

include/linux/fuse.h

@@ -25,6 +25,9 @@
  *  - add IOCTL message
  *  - add unsolicited notification support
  *  - add POLL message and NOTIFY_POLL notification
+ *
+ * 7.12
+ *  - add umask flag to input argument of open, mknod and mkdir
  */
 
 #ifndef _LINUX_FUSE_H
@@ -36,7 +39,7 @@
 #define FUSE_KERNEL_VERSION 7
 
 /** Minor version number of this interface */
-#define FUSE_KERNEL_MINOR_VERSION 11
+#define FUSE_KERNEL_MINOR_VERSION 12
 
 /** The node ID of the root inode */
 #define FUSE_ROOT_ID 1
@@ -112,13 +115,15 @@ struct fuse_file_lock {
  * INIT request/reply flags
  *
  * FUSE_EXPORT_SUPPORT: filesystem handles lookups of "." and ".."
+ * FUSE_DONT_MASK: don't apply umask to file mode on create operations
  */
 #define FUSE_ASYNC_READ		(1 << 0)
 #define FUSE_POSIX_LOCKS	(1 << 1)
 #define FUSE_FILE_OPS		(1 << 2)
 #define FUSE_ATOMIC_O_TRUNC	(1 << 3)
 #define FUSE_EXPORT_SUPPORT	(1 << 4)
 #define FUSE_BIG_WRITES		(1 << 5)
+#define FUSE_DONT_MASK		(1 << 6)
 
 /**
  * CUSE INIT request/reply flags
@@ -262,14 +267,18 @@ struct fuse_attr_out {
 	struct fuse_attr attr;
 };
 
+#define FUSE_COMPAT_MKNOD_IN_SIZE 8
+
 struct fuse_mknod_in {
 	__u32	mode;
 	__u32	rdev;
+	__u32	umask;
+	__u32	padding;
 };
 
 struct fuse_mkdir_in {
 	__u32	mode;
-	__u32	padding;
+	__u32	umask;
 };
 
 struct fuse_rename_in {
@@ -300,8 +309,15 @@ struct fuse_setattr_in {
 };
 
 struct fuse_open_in {
+	__u32	flags;
+	__u32	unused;
+};
+
+struct fuse_create_in {
 	__u32	flags;
 	__u32	mode;
+	__u32	umask;
+	__u32	padding;
 };
 
 struct fuse_open_out {