From: Will Deacon <will@kernel.org>
To: Xu Kuohai <xukuohai@huaweicloud.com>
Cc: Fuad Tabba <tabba@google.com>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Puranjay Mohan <puranjay@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
bpf@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org,
Martin KaFai Lau <martin.lau@linux.dev>,
Eduard Zingerman <eddyz87@gmail.com>, Song Liu <song@kernel.org>,
Yonghong Song <yonghong.song@linux.dev>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
Stanislav Fomichev <sdf@fomichev.me>, Hao Luo <haoluo@google.com>,
Jiri Olsa <jolsa@kernel.org>,
Jakub Sitnicki <jakub@cloudflare.com>,
Jean-Philippe Brucker <jpb@kernel.org>
Subject: Re: [PATCH] arm64: bpf: Fix UBSAN misaligned access in BPF JIT
Date: Wed, 25 Feb 2026 17:47:58 +0000 [thread overview]
Message-ID: <aZ81zpP6ooG_19cI@willie-the-truck> (raw)
In-Reply-To: <2d0c6893-d4a5-42bc-a480-55bc669da130@huaweicloud.com>
On Wed, Feb 25, 2026 at 05:46:52PM +0800, Xu Kuohai wrote:
> Interesting, I think the plt target should be 64-bit aligned to ensure
> atomic reading on arm64. It can be updated concurrently by WRITE_ONCE
> in the bpf_arch_text_poke function while the ldr instruction in the plt is
> executed. If it is not aligned correctly, the ldr may read a half-old
> half-new value, causing the plt to jump to an invalid destination.
Thanks for pointing that out; I hadn't realised that we patched live
PLTs!
> To avoid over-aligning the entire buffer, how about fixing the padding
> method in build_plt to just make the plt target aligned correctly?
Makes sense to me.
Will
next prev parent reply other threads:[~2026-02-25 17:48 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-24 9:31 Fuad Tabba
2026-02-25 1:43 ` Xu Kuohai
2026-02-25 9:08 ` Fuad Tabba
2026-02-25 9:46 ` Xu Kuohai
2026-02-25 11:00 ` Fuad Tabba
2026-02-26 1:34 ` Xu Kuohai
2026-02-26 7:55 ` [PATCH v3] arm64: bpf: Force 8-byte alignment for JIT buffer to prevent atomic tearing Fuad Tabba
2026-02-26 18:28 ` Will Deacon
2026-02-26 19:30 ` patchwork-bot+netdevbpf
2026-02-25 17:47 ` Will Deacon [this message]
2026-02-25 17:53 ` [PATCH] arm64: bpf: Fix UBSAN misaligned access in BPF JIT Fuad Tabba
2026-02-25 18:22 ` Will Deacon
-- strict thread matches above, loose matches on Subject: below --
2026-02-24 9:29 Fuad Tabba
2026-02-24 22:11 ` Will Deacon
2026-02-25 9:07 ` Fuad Tabba
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