From: Martin KaFai Lau <martin.lau@linux.dev>
To: rtm@csail.mit.edu
Cc: bpf@vger.kernel.org, netdev@vger.kernel.org
Subject: Re: unregistering tcp_ca struct_ops can cause kernel page fault
Date: Fri, 13 Dec 2024 16:56:59 -0800 [thread overview]
Message-ID: <ac054b6e-2120-4598-b960-ddd275714218@linux.dev> (raw)
In-Reply-To: <96319.1733959698@localhost>
On 12/11/24 3:28 PM, rtm@csail.mit.edu wrote:
> Martin,
>
> When I build from bpf-next/master with a default .config, I do not get
> the crash.
>
> When I disable CONFIG_MODULES, I do get a crash from tcpbps12a.c.
During make:
"WARN: resolve_btfids: unresolved symbol module"
Without going into the details, the bpf_try_module_get failed to bump the refcnt
because of missing the "struct module" btf_id.
With a quick thought, I see bpf_struct_ops should be able to work around this
CONFIG_MODULES=n.
I don't think it should though. The bpf_tcp_ca is using the "struct
tcp_congestion_ops" which can be implemented by a kernel module and the kconfig
wants nothing other than the built-in tcp-cc. I don't think the bpf_struct_ops
should be a way to work around that. I think the right thing to do here is to
also disallow attaching bpf_struct_ops when CONFIG_MODULES=n to fix this UAF issue.
prev parent reply other threads:[~2024-12-14 0:57 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-12-08 14:59 unregistering tcp_ca struct_ops can cause kernel page fault rtm
2024-12-09 21:56 ` Martin KaFai Lau
2024-12-11 23:28 ` rtm
2024-12-14 0:56 ` Martin KaFai Lau [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=ac054b6e-2120-4598-b960-ddd275714218@linux.dev \
--to=martin.lau@linux.dev \
--cc=bpf@vger.kernel.org \
--cc=netdev@vger.kernel.org \
--cc=rtm@csail.mit.edu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).