From: "Björn Töpel" <bjorn@kernel.org>
To: Feng Jiang <jiangfeng@kylinos.cn>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Eduard Zingerman <eddyz87@gmail.com>,
Kumar Kartikeya Dwivedi <memxor@gmail.com>,
Martin KaFai Lau <martin.lau@linux.dev>,
Song Liu <song@kernel.org>,
Yonghong Song <yonghong.song@linux.dev>,
Jiri Olsa <jolsa@kernel.org>,
Emil Tsalapatis <emil@etsalapatis.com>,
Pu Lehui <pulehui@huawei.com>,
Puranjay Mohan <puranjay@kernel.org>,
Paul Walmsley <pjw@kernel.org>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>,
Alexandre Ghiti <alex@ghiti.fr>
Cc: "Björn Töpel" <bjorn@rivosinc.com>,
bpf@vger.kernel.org, linux-riscv@lists.infradead.org,
linux-kernel@vger.kernel.org, "Feng Jiang" <jiangfeng@kylinos.cn>
Subject: Re: [PATCH v3] bpf, riscv: fix extable handling for arena load_acquire
Date: Tue, 21 Jul 2026 20:17:48 +0200 [thread overview]
Message-ID: <87h5lsurzn.fsf@all.your.base.are.belong.to.us> (raw)
In-Reply-To: <20260720-bpf-riscv-fix-extable-v3-1-e9a603882309@kylinos.cn>
Feng Jiang <jiangfeng@kylinos.cn> writes:
> emit_atomic_ld_st() returns 1 to have build_body() skip the zext after
> a sub-word load_acquire. The caller does "ret = ret ?:
> add_exception_handler(...)", which skips add_exception_handler() on any
> non-zero ret, so the extable entry is missing and a faulting
> PROBE_ATOMIC load_acquire oopses.
>
> REG_DONT_CLEAR_MARKER leaves rd stale on fault, and the verifier still
> thinks the load overwrote it, so a program can leak it through a map.
>
> Check ret >= 0 before calling add_exception_handler(), and pass rd for
> LOAD_ACQ so the fault zeroes rd like a PROBE_MEM load. Return ret
> unchanged for the zext skip.
>
> Fixes: fb7cefabae81 ("riscv, bpf: Add support arena atomics for RV64")
> Signed-off-by: Feng Jiang <jiangfeng@kylinos.cn>
Thank you for spinning a new version!
Reviewed-by: Björn Töpel <bjorn@kernel.org>
Acked-by: Björn Töpel <bjorn@kernel.org>
next prev parent reply other threads:[~2026-07-21 18:17 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-20 6:06 Feng Jiang
2026-07-21 18:17 ` Björn Töpel [this message]
2026-07-21 18:25 ` Kumar Kartikeya Dwivedi
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