Re: [PATCH 0/2] Prevent potential write out of bounds

[Joao Moreira]

On 2023-08-31 18:28, Jakub Kicinski wrote:
> On Thu, 31 Aug 2023 18:04:35 -0700 joao@xxxxxxxxxxxxxxxxxx wrote:
> > The function flow_rule_alloc in net/core/flow_offload.c [2] gets an
> > unsigned int num_actions (line 10) and later traverses the actions in
> > the rule (line 24) setting hw.stats to FLOW_ACTION_HW_STATS_DONT_CARE.
> >
> > Within the same file, the loop in the line 24 compares a signed int
> > (i) to an unsigned int (num_actions), and then uses i as an array
> > index. If an integer overflow happens, then the array within the loop
> > is wrongly indexed, causing a write out of bounds.
> >
> > After checking with maintainers, it seems that the front-end caps the
> > maximum value of num_action, thus it is not possible to reach the 
> > given
> > write out of bounds, yet, still, to prevent disasters it is better to
> > fix the signedness here.
>
> How did you find this? The commit messages should include info
> about how the issue was discovered.

Sure, I'll wait a bit longer for more suggestions and add the info in a 
next patch version.

Meanwhile, fwiiw, I stumbled on the bug when I was reading Nick 
Gregory's write-up on CVE-2022-25636 [1], which happens nearby but is 
not exactly this issue.

Tks,
Joao

[1] - https://nickgregory.me/post/2022/03/12/cve-2022-25636/