Re: [Linux-kernel-mentees] [PATCH net] AX.25: Prevent out-of-bounds read in ax25_sendmsg()

From: David Ranch
Date: Fri Jul 24 2020 - 19:28:52 EST

I need to ask the following question to the Linux kernel community as the AX25 amateur radio community is already having to
work around a few broken commits that were committed 4.1.22+:

Is anyone actually _*testing*_ these proposed changes to make sure the AX.25 and related ecosystem still work afterwards?

I've personally tried multiple times to recruit some help to get some of these previous commits rolled back from some
recommended kernel people including even some the original authors like Alan Cox, etc without any success. I fear that if
more commits come into the kernel without any testing, the whole AX.25 stack will become toxic and unusable.

I am not a kernel class developer but I am *personally* willing to help out on the testing effort and even help setup regression
topologies (VMs, containers, whatever) if there is some place that they can be ideally run in a continuous delivery.

If there is anyone also willing to help fix some of these previous commits and get the AX.25 stack kernel back on track,
I do have a bunch of details of the commit details, details on why those committers THOUGHT they were a good idea, etc.


On 07/22/2020 06:07 PM, David Miller wrote:
From: Peilin Ye <yepeilin.cs@xxxxxxxxx>
Date: Wed, 22 Jul 2020 12:05:12 -0400

Checks on `addr_len` and `usax->sax25_ndigis` are insufficient.
ax25_sendmsg() can go out of bounds when `usax->sax25_ndigis` equals to 7
or 8. Fix it.

It is safe to remove `usax->sax25_ndigis > AX25_MAX_DIGIS`, since
`addr_len` is guaranteed to be less than or equal to
`sizeof(struct full_sockaddr_ax25)`

Signed-off-by: Peilin Ye <yepeilin.cs@xxxxxxxxx>