fuse: verify ioctl retries

Verify that the total length of the iovec returned in FUSE_IOCTL_RETRY
doesn't overflow iov_length().
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
CC: Tejun Heo <tj@kernel.org>
CC: <stable@kernel.org>         [2.6.31+]

fs/fuse/file.c

@@ -1666,6 +1666,20 @@ static int fuse_copy_ioctl_iovec(struct iovec *dst, void *src,
 	return 0;
 }
 
+/* Make sure iov_length() won't overflow */
+static int fuse_verify_ioctl_iov(struct iovec *iov, size_t count)
+{
+	size_t n;
+	u32 max = FUSE_MAX_PAGES_PER_REQ << PAGE_SHIFT;
+
+	for (n = 0; n < count; n++) {
+		if (iov->iov_len > (size_t) max)
+			return -ENOMEM;
+		max -= iov->iov_len;
+	}
+	return 0;
+}
+
 /*
  * For ioctls, there is no generic way to determine how much memory
  * needs to be read and/or written.  Furthermore, ioctls are allowed
@@ -1858,6 +1872,14 @@ long fuse_do_ioctl(struct file *file, unsigned int cmd, unsigned long arg,
 		in_iov = page_address(iov_page);
 		out_iov = in_iov + in_iovs;
 
+		err = fuse_verify_ioctl_iov(in_iov, in_iovs);
+		if (err)
+			goto out;
+
+		err = fuse_verify_ioctl_iov(out_iov, out_iovs);
+		if (err)
+			goto out;
+
 		goto retry;
 	}