On 31/05/2019 15:44, Kees Cook wrote:

On Fri, May 31, 2019 at 11:46:29AM +0100, Colin Ian King wrote:

quoted

Hi,

Static analysis with Coverity on linux-next has found a potential issue
with the following commit:

commit 1633a4f04cc171fc638deb5c95af96032d3c591b
Author: Ke Wu [off-list ref]
Date:   Thu May 30 12:22:08 2019 -0700

    security/loadpin: Allow to exclude specific file types


209                for (j = 0; j < ARRAY_SIZE(kernel_read_file_str); j++) {
210                        if (strcmp(cur, kernel_read_file_str[j]) == 0) {
211                                pr_info("excluding: %s\n",
212                                        kernel_read_file_str[j]);

CID 81977 (#1 of 1): Out-of-bounds write
overrun-local: Overrunning array ignore_read_file_id of 8 4-byte
elements at element index 8 (byte offset 35) using index j (which
evaluates to 8).

213                                ignore_read_file_id[j] = 1;

According to Coverity ignore_read_file_id is an array of 8 integers.
However, ARRAY_SIZE(kernel_read_file_str) is 9, so we have an out of
bounds write on ignore_read_file[j] when j is 8.

What am I missing? This doesn't fail the build:

+       BUILD_BUG_ON(ARRAY_SIZE(exclude_read_files) !=
+                    ARRAY_SIZE(ignore_read_file_id));

They have the same number of elements.

Yep, that's very true. I'll discuss this with Coverity as this seems
like a weird false positive.

Apologies for the noise.

Colin