[PATCH 5.15 094/244] NTB: ntb_tool: uninitialized heap data in tool_fn_write()

Greg Kroah-Hartman
2022-08-23T10:02:44Z

From: Dan Carpenter <dan.carpenter@oracle.com>

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>
---
drivers/ntb/test/ntb_tool.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

--- 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
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;