From: John Fastabend <john.fastabend@gmail.com>
To: Vuln seeker Cyber Security Team <security@vulnseeker.org>
Cc: bpf@vger.kernel.org
Subject: Re: Responsible Disclosure: Heap Out-of-Bounds Write via Integer Underflow in libbpf parse_cpu_mask_str() (libbpf.c:14446)
Date: Tue, 7 Jul 2026 07:47:32 -0700 [thread overview]
Message-ID: <ak0QM9G74dc3jpWc@john-p8> (raw)
In-Reply-To: <CAO_sQLjn=hghkb7SZr2UWexf=opgLTu5_AHR2uTQrJ1r13vpjg@mail.gmail.com>
On Fri, Jul 03, 2026 at 05:22:30PM +0500, Vuln seeker Cyber Security Team wrote:
>Dear libbpf Security Team,
[...]
>libbpf's CPU mask parser. An integer underflow in parse_cpu_mask_str()
>causes a memset to write far past a shrunk heap allocation, reachable
>end-to-end through the public libbpf_num_possible_cpus() API.
Send the fix seems worth checking to me if we are already checking
start/end. If some app is exposing user input to this then I would
push a report to them.
[...]
> - Any downstream consumer that feeds untrusted CPU-mask strings to
> the
>internal parse_cpu_mask_str helper directly
Not sure why untrusted input is getting here but sure if someone
is piping user input to libbpf let them know. I think if you have
untrusted user input hitting libbpf you have bigger problems.
[...]
>
> if (start < *mask_sz)
> return -EINVAL; // "CPU range out of order or overlapping"
>
Send a fix. Thanks.
next prev parent reply other threads:[~2026-07-07 14:47 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-03 12:22 Responsible Disclosure: Heap Out-of-Bounds Write via Integer Underflow in libbpf parse_cpu_mask_str() (libbpf.c:14446) Vuln seeker Cyber Security Team
2026-07-07 14:47 ` John Fastabend [this message]
2026-07-08 7:33 ` Vuln seeker Cyber Security Team
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