netdev - Re: [PATCH bpf] riscv, bpf: Fix possible infinite tailcall when CONFIG_CFI

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Message-ID: <87jzeh4qvv.fsf@all.your.base.are.belong.to.us>
Date: Wed, 09 Oct 2024 10:33:40 +0200
From: Björn Töpel <bjorn@...nel.org>
To: Pu Lehui <pulehui@...weicloud.com>, bpf@...r.kernel.org,
 linux-riscv@...ts.infradead.org, netdev@...r.kernel.org
Cc: Puranjay Mohan <puranjay@...nel.org>, Alexei Starovoitov
 <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko
 <andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, Eduard
 Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, Yonghong Song
 <yonghong.song@...ux.dev>, John Fastabend <john.fastabend@...il.com>, KP
 Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>, Hao Luo
 <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, Palmer Dabbelt
 <palmer@...belt.com>, Paul Walmsley <paul.walmsley@...ive.com>, Albert Ou
 <aou@...s.berkeley.edu>
Subject: Re: [PATCH bpf] riscv, bpf: Fix possible infinite tailcall when
 CONFIG_CFI_CLANG is enabled

Pu Lehui <pulehui@...weicloud.com> writes:

> From: Pu Lehui <pulehui@...wei.com>
>
> When CONFIG_CFI_CLANG is enabled, the number of prologue instructions
> skipped by tailcall needs to include the kcfi instruction, otherwise the
> TCC will be initialized every tailcall is called, which may result in
> infinite tailcalls.
>
> Fixes: e63985ecd226 ("bpf, riscv64/cfi: Support kCFI + BPF on riscv64")
> Signed-off-by: Pu Lehui <pulehui@...wei.com>

Thanks! Did you test this with the selftest suite? Did the tailcall
tests catch it?

Note to self is that I should run kCFI enabled tests for RISC-V.


Acked-by: Björn Töpel <bjorn@...nel.org>