[PATCH] FUSE: pass file handle in setattr

This patch passes the file handle supplied in iattr to userspace, in case the
->setattr() was invoked from sys_ftruncate().  This solves the permission
checking (or lack thereof) in ftruncate() for the class of filesystems served
by an unprivileged userspace process.

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/fuse/dir.c

@@ -763,29 +763,29 @@ static int fuse_dir_fsync(struct file *file, struct dentry *de, int datasync)
 	return file ? fuse_fsync_common(file, de, datasync, 1) : 0;
 }
 
-static unsigned iattr_to_fattr(struct iattr *iattr, struct fuse_attr *fattr)
+static void iattr_to_fattr(struct iattr *iattr, struct fuse_setattr_in *arg)
 {
 	unsigned ivalid = iattr->ia_valid;
-	unsigned fvalid = 0;
-
-	memset(fattr, 0, sizeof(*fattr));
 
 	if (ivalid & ATTR_MODE)
-		fvalid |= FATTR_MODE,   fattr->mode = iattr->ia_mode;
+		arg->valid |= FATTR_MODE,   arg->mode = iattr->ia_mode;
 	if (ivalid & ATTR_UID)
-		fvalid |= FATTR_UID,    fattr->uid = iattr->ia_uid;
+		arg->valid |= FATTR_UID,    arg->uid = iattr->ia_uid;
 	if (ivalid & ATTR_GID)
-		fvalid |= FATTR_GID,    fattr->gid = iattr->ia_gid;
+		arg->valid |= FATTR_GID,    arg->gid = iattr->ia_gid;
 	if (ivalid & ATTR_SIZE)
-		fvalid |= FATTR_SIZE,   fattr->size = iattr->ia_size;
+		arg->valid |= FATTR_SIZE,   arg->size = iattr->ia_size;
 	/* You can only _set_ these together (they may change by themselves) */
 	if ((ivalid & (ATTR_ATIME | ATTR_MTIME)) == (ATTR_ATIME | ATTR_MTIME)) {
-		fvalid |= FATTR_ATIME | FATTR_MTIME;
-		fattr->atime = iattr->ia_atime.tv_sec;
-		fattr->mtime = iattr->ia_mtime.tv_sec;
+		arg->valid |= FATTR_ATIME | FATTR_MTIME;
+		arg->atime = iattr->ia_atime.tv_sec;
+		arg->mtime = iattr->ia_mtime.tv_sec;
+	}
+	if (ivalid & ATTR_FILE) {
+		struct fuse_file *ff = iattr->ia_file->private_data;
+		arg->valid |= FATTR_FH;
+		arg->fh = ff->fh;
 	}
-
-	return fvalid;
 }
 
 static int fuse_setattr(struct dentry *entry, struct iattr *attr)
@@ -820,7 +820,7 @@ static int fuse_setattr(struct dentry *entry, struct iattr *attr)
 		return -EINTR;
 
 	memset(&inarg, 0, sizeof(inarg));
-	inarg.valid = iattr_to_fattr(attr, &inarg.attr);
+	iattr_to_fattr(attr, &inarg);
 	req->in.h.opcode = FUSE_SETATTR;
 	req->in.h.nodeid = get_node_id(inode);
 	req->inode = inode;

include/linux/fuse.h

@@ -61,6 +61,7 @@ struct fuse_kstatfs {
 #define FATTR_SIZE	(1 << 3)
 #define FATTR_ATIME	(1 << 4)
 #define FATTR_MTIME	(1 << 5)
+#define FATTR_FH	(1 << 6)
 
 /**
  * Flags returned by the OPEN request
@@ -154,7 +155,20 @@ struct fuse_link_in {
 struct fuse_setattr_in {
 	__u32	valid;
 	__u32	padding;
-	struct fuse_attr attr;
+	__u64	fh;
+	__u64	size;
+	__u64	unused1;
+	__u64	atime;
+	__u64	mtime;
+	__u64	unused2;
+	__u32	atimensec;
+	__u32	mtimensec;
+	__u32	unused3;
+	__u32	mode;
+	__u32	unused4;
+	__u32	uid;
+	__u32	gid;
+	__u32	unused5;
 };
 
 struct fuse_open_in {