[PATCH] fuse: clean up request size limit checking

Change the way a too large request is handled.  Until now in this case the
device read returned -EINVAL and the operation returned -EIO.

Make it more flexibible by not returning -EINVAL from the read, but restarting
it instead.

Also remove the fixed limit on setxattr data and let the filesystem provide as
large a read buffer as it needs to handle the extended attribute data.

The symbolic link length is already checked by VFS to be less than PATH_MAX,
so the extra check against FUSE_SYMLINK_MAX is not needed.

The check in fuse_create_open() against FUSE_NAME_MAX is not needed, since the
dentry has already been looked up, and hence the name already checked.
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/dev.c

@@ -617,6 +617,7 @@ static ssize_t fuse_dev_readv(struct file *file, const struct iovec *iov,
 	struct fuse_copy_state cs;
 	unsigned reqsize;
 
+ restart:
 	spin_lock(&fuse_lock);
 	fc = file->private_data;
 	err = -EPERM;
@@ -632,20 +633,25 @@ static ssize_t fuse_dev_readv(struct file *file, const struct iovec *iov,
 
 	req = list_entry(fc->pending.next, struct fuse_req, list);
 	list_del_init(&req->list);
-	spin_unlock(&fuse_lock);
 
 	in = &req->in;
-	reqsize = req->in.h.len;
+	reqsize = in->h.len;
+	/* If request is too large, reply with an error and restart the read */
+	if (iov_length(iov, nr_segs) < reqsize) {
+		req->out.h.error = -EIO;
+		/* SETXATTR is special, since it may contain too large data */
+		if (in->h.opcode == FUSE_SETXATTR)
+			req->out.h.error = -E2BIG;
+		request_end(fc, req);
+		goto restart;
+	}
+	spin_unlock(&fuse_lock);
 	fuse_copy_init(&cs, 1, req, iov, nr_segs);
-	err = -EINVAL;
-	if (iov_length(iov, nr_segs) >= reqsize) {
 	err = fuse_copy_one(&cs, &in->h, sizeof(in->h));
 	if (!err)
 		err = fuse_copy_args(&cs, in->numargs, in->argpages,
 				     (struct fuse_arg *) in->args, 0);
-	}
 	fuse_copy_finish(&cs);
-
 	spin_lock(&fuse_lock);
 	req->locked = 0;
 	if (!err && req->interrupted)

fs/fuse/dir.c

@@ -236,10 +236,6 @@ static int fuse_create_open(struct inode *dir, struct dentry *entry, int mode,
 	if (fc->no_create)
 		goto out;
 
-	err = -ENAMETOOLONG;
-	if (entry->d_name.len > FUSE_NAME_MAX)
-		goto out;
-
 	err = -EINTR;
 	req = fuse_get_request(fc);
 	if (!req)
@@ -413,12 +409,7 @@ static int fuse_symlink(struct inode *dir, struct dentry *entry,
 {
 	struct fuse_conn *fc = get_fuse_conn(dir);
 	unsigned len = strlen(link) + 1;
-	struct fuse_req *req;
-
-	if (len > FUSE_SYMLINK_MAX)
-		return -ENAMETOOLONG;
-
-	req = fuse_get_request(fc);
+	struct fuse_req *req = fuse_get_request(fc);
 	if (!req)
 		return -EINTR;
 
@@ -988,9 +979,6 @@ static int fuse_setxattr(struct dentry *entry, const char *name,
 	struct fuse_setxattr_in inarg;
 	int err;
 
-	if (size > FUSE_XATTR_SIZE_MAX)
-		return -E2BIG;
-
 	if (fc->no_setxattr)
 		return -EOPNOTSUPP;
 

fs/fuse/fuse_i.h

@@ -21,6 +21,12 @@
 /** If more requests are outstanding, then the operation will block */
 #define FUSE_MAX_OUTSTANDING 10
 
+/** Maximum size of data in a write request */
+#define FUSE_MAX_WRITE 4096
+
+/** It could be as large as PATH_MAX, but would that have any uses? */
+#define FUSE_NAME_MAX 1024
+
 /** If the FUSE_DEFAULT_PERMISSIONS flag is given, the filesystem
     module will check permissions based on the file mode.  Otherwise no
     permission checking is done in the kernel */
@@ -108,9 +114,6 @@ struct fuse_out {
 	struct fuse_arg args[3];
 };
 
-struct fuse_req;
-struct fuse_conn;
-
 /**
  * A request to the client
  */

fs/fuse/inode.c

@@ -485,7 +485,7 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)
 	fc->max_read = d.max_read;
 	if (fc->max_read / PAGE_CACHE_SIZE < fc->bdi.ra_pages)
 		fc->bdi.ra_pages = fc->max_read / PAGE_CACHE_SIZE;
-	fc->max_write = FUSE_MAX_IN / 2;
+	fc->max_write = FUSE_MAX_WRITE;
 
 	err = -ENOMEM;
 	root = get_root_inode(sb, d.rootmode);

include/linux/fuse.h

@@ -108,12 +108,8 @@ enum fuse_opcode {
 	FUSE_CREATE        = 35
 };
 
-/* Conservative buffer size for the client */
-#define FUSE_MAX_IN 8192
-
-#define FUSE_NAME_MAX 1024
-#define FUSE_SYMLINK_MAX 4096
-#define FUSE_XATTR_SIZE_MAX 4096
+/* The read buffer is required to be at least 8k, but may be much larger */
+#define FUSE_MIN_READ_BUFFER 8192
 
 struct fuse_entry_out {
 	__u64	nodeid;		/* Inode ID */