NTB: ntb_tool: uninitialized heap data in tool_fn_write()

commit 45e1058b77feade4e36402828bfe3e0d3363177b upstream.

The call to:

	ret = simple_write_to_buffer(buf, size, offp, ubuf, size);

will return success if it is able to write even one byte to "buf".
The value of "*offp" controls which byte.  This could result in
reading uninitialized data when we do the sscanf() on the next line.

This code is not really desigined to handle partial writes where
*offp is non-zero and the "buf" is preserved and re-used between writes.
Just ban partial writes and replace the simple_write_to_buffer() with
copy_from_user().

Fixes: 578b881ba9c4 ("NTB: Add tool test client")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/ntb/test/ntb_tool.c b/drivers/ntb/test/ntb_tool.c
index b7bf3f863d79b45e625273ae15fb8712819b1c04..5ee0afa621a9503c34dbcfb32421a990a00abf47 100644 (file)
--- a/drivers/ntb/test/ntb_tool.c
+++ b/drivers/ntb/test/ntb_tool.c
@@ -367,14 +367,16 @@ static ssize_t tool_fn_write(struct tool_ctx *tc,
        u64 bits;
        int n;
 
+       if (*offp)
+               return 0;
+
        buf = kmalloc(size + 1, GFP_KERNEL);
        if (!buf)
                return -ENOMEM;
 
-       ret = simple_write_to_buffer(buf, size, offp, ubuf, size);
-       if (ret < 0) {
+       if (copy_from_user(buf, ubuf, size)) {
                kfree(buf);
-               return ret;
+               return -EFAULT;
        }
 
        buf[size] = 0;