linux-kernel - Re: [PATCH bpf] selftests/bpf: DENYLIST.aarch64: Remove fexit

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Message-ID: <CAADnVQJXcGB69o1s5GcLYV=OYS+hmqxGJVvtDH3YrVQc1o_=Tg@mail.gmail.com>
Date: Fri, 12 Jul 2024 09:07:12 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Daniel Borkmann <daniel@...earbox.net>
Cc: Puranjay Mohan <puranjay@...nel.org>, Manu Bretelle <chantra@...a.com>, KP Singh <kpsingh@...nel.org>, 
	Andrii Nakryiko <andrii@...nel.org>, Eduard Zingerman <eddyz87@...il.com>, Mykola Lysenko <mykolal@...a.com>, 
	Alexei Starovoitov <ast@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, Song Liu <song@...nel.org>, 
	Yonghong Song <yonghong.song@...ux.dev>, John Fastabend <john.fastabend@...il.com>, 
	Stanislav Fomichev <sdf@...gle.com>, Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, 
	Shuah Khan <shuah@...nel.org>, "bpf@...r.kernel.org" <bpf@...r.kernel.org>, 
	"linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Florent Revest <revest@...gle.com>
Subject: Re: [PATCH bpf] selftests/bpf: DENYLIST.aarch64: Remove fexit_sleep

On Fri, Jul 12, 2024 at 6:50 AM Daniel Borkmann <daniel@...earbox.net> wrote:
>
> Hi Puranjay,
>
> On 7/11/24 4:00 PM, Puranjay Mohan wrote:
> [...]
> > I was able find the root cause of this bug and will send a fix soon!
> >
> >> Unable to handle kernel paging request at virtual address ffff0000c2a80e68
> >
> > We are running this test on Qemu with '-cpu max', this means 52-bit
> > virtual addresses are being used.
> >
> > The trampolines generation code has the following two lines:
> >
> >               emit_addr_mov_i64(A64_R(0), (const u64)im, ctx);
> >               emit_call((const u64)__bpf_tramp_enter, ctx);
> >
> > here the address of struct bpf_tramp_image is moved to R0 and passed as
> > an argument to __bpf_tramp_enter().
> >
> > emit_addr_mov_i64() assumes that the address passed to it is in the
> > vmalloc space and uses at most 48 bits. It sets all the remaining bits
> > to 1.
> >
> > but struct bpf_tramp_image is allocated using kzalloc() and when 52-bit
> > VAs are used, its address is not guaranteed to be 48-bit, therefore we
> > see this bug, where  0xfff[0]0000c2a80e68 is converted to
> > 0xfff[f]0000c2a80e68 when the trampoline is generated.
> >
> > The fix would be use emit_a64_mov_i64() for moving this address into R0.
>
> It looks like there is still an issue left. A recent CI run on bpf-next is
> still hitting the same on arm64:
>
> Base:
>
>    https://github.com/kernel-patches/bpf/commits/series/870746%3D%3Ebpf-next/
>
> CI:
>
>    https://github.com/kernel-patches/bpf/actions/runs/9905842936/job/27366435436
>
>    [...]
>    #89/11   fexit_bpf2bpf/func_replace_global_func:OK
>    #89/12   fexit_bpf2bpf/fentry_to_cgroup_bpf:OK
>    #89/13   fexit_bpf2bpf/func_replace_progmap:OK
>    #89      fexit_bpf2bpf:OK
>    Error: The operation was canceled.

Let's denylist that test again for now?