ntb_tool: BUG: Ensure the buffer size is large enough to return all spads

On hardware with 32 scratchpad registers the spad field in ntb tool
could chop off the end. The maximum buffer size is increased from
256 to 15 times the number or scratchpads.
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Acked-by: Allen Hubbe <Allen.Hubbe@emc.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>

drivers/ntb/test/ntb_tool.c

@@ -239,7 +239,14 @@ static ssize_t tool_spadfn_read(struct tool_ctx *tc, char __user *ubuf,
 	if (!spad_read_fn)
 		return -EINVAL;
 
-	buf_size = min_t(size_t, size, 0x100);
+	spad_count = ntb_spad_count(tc->ntb);
+
+	/*
+	 * We multiply the number of spads by 15 to get the buffer size
+	 * this is from 3 for the %d, 10 for the largest hex value
+	 * (0x00000000) and 2 for the tab and line feed.
+	 */
+	buf_size = min_t(size_t, size, spad_count * 15);
 
 	buf = kmalloc(buf_size, GFP_KERNEL);
 	if (!buf)
@@ -247,7 +254,6 @@ static ssize_t tool_spadfn_read(struct tool_ctx *tc, char __user *ubuf,
 
 	pos = 0;
 
-	spad_count = ntb_spad_count(tc->ntb);
 	for (i = 0; i < spad_count; ++i) {
 		pos += scnprintf(buf + pos, buf_size - pos, "%d\t%#x\n",
 				 i, spad_read_fn(tc->ntb, i));