linux-kernel - Re: bpf: incorrect stack_depth after var off stack access causes OOB

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Message-ID: <CABWLsesED+S_XNnWJDvJnPV7D0K5U4y3VjGQ7EKeecnufw4xbQ@mail.gmail.com>
Date:   Mon, 13 Nov 2023 19:03:43 -0500
From:   Andrei Matei <andreimatei1@...il.com>
To:     Hao Sun <sunhao.th@...il.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        John Fastabend <john.fastabend@...il.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>,
        Yonghong Song <yonghong.song@...ux.dev>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Jiri Olsa <jolsa@...nel.org>, bpf <bpf@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: bpf: incorrect stack_depth after var off stack access causes OOB

I have sent https://lore.kernel.org/bpf/20231113235008.127238-1-andreimatei1@gmail.com/T/#u
as a fix.

Hao, thanks again for the report. For my edification, how did you get
the KASAN bug report with your repro / which tree exactly were you
running against and with what config? I've run your repro program in
the VM created by vmtest.sh, with an added CONFIG_KASAN=y in the
config, and I did not get the bug report in dmesg; I got nothing.
However, if I change the variable offset bounds to be around 200 bytes
instead of 12, then I do get a kernel panic because of a page fault.