From: Peter Zijlstra <peterz@infradead.org>
To: Jiri Olsa <olsajiri@gmail.com>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>,
Song Liu <song@kernel.org>, Song Liu <songliubraving@meta.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
X86 ML <x86@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
"David S. Miller" <davem@davemloft.net>,
David Ahern <dsahern@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <martin.lau@linux.dev>,
Yonghong Song <yonghong.song@linux.dev>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>,
Arnd Bergmann <arnd@arndb.de>,
Sami Tolvanen <samitolvanen@google.com>,
Kees Cook <keescook@chromium.org>,
Nathan Chancellor <nathan@kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>,
linux-riscv <linux-riscv@lists.infradead.org>,
LKML <linux-kernel@vger.kernel.org>,
Network Development <netdev@vger.kernel.org>,
bpf <bpf@vger.kernel.org>,
linux-arch <linux-arch@vger.kernel.org>,
clang-built-linux <llvm@lists.linux.dev>,
Josh Poimboeuf <jpoimboe@kernel.org>,
Joao Moreira <joao@overdrivepizza.com>,
Mark Rutland <mark.rutland@arm.com>
Subject: Re: [PATCH v2 2/2] x86/cfi,bpf: Fix BPF JIT call
Date: Mon, 4 Dec 2023 19:33:54 +0100 [thread overview]
Message-ID: <20231204183354.GC7299@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <20231204181614.GA7299@noisy.programming.kicks-ass.net>
On Mon, Dec 04, 2023 at 07:16:14PM +0100, Peter Zijlstra wrote:
> On Mon, Dec 04, 2023 at 06:25:34PM +0100, Jiri Olsa wrote:
>
> > that boots properly for me but gives crash below when running bpf tests
>
> OK, more funnies..
>
> > [ 482.145182][ T699] RIP: 0010:bpf_for_each_array_elem+0xbb/0x120
> > [ 482.145672][ T699] Code: 4c 01 f5 89 5c 24 04 4c 89 e7 48 8d 74 24 04 48 89 ea 4c 89 fd 4c 89 f9 45 31 c0 4d 89 eb 41 ba ef 86 cd 67 45 03 53 f1 74 02 <0f> 0b 41 ff d3 0f 1f 00 48 85 c0 75 0e 48 8d 43 01 41 8b 4c 24 24
> > [ 482.147221][ T699] RSP: 0018:ffffc900017e3e88 EFLAGS: 00010217
> > [ 482.147702][ T699] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffc900017e3ed8
> > [ 482.152162][ T699] RDX: ffff888152eb0210 RSI: ffffc900017e3e8c RDI: ffff888152eb0000
> > [ 482.152770][ T699] RBP: ffffc900017e3ed8 R08: 0000000000000000 R09: 0000000000000000
> > [ 482.153350][ T699] R10: 000000004704ef28 R11: ffffffffa0012774 R12: ffff888152eb0000
> > [ 482.153951][ T699] R13: ffffffffa0012774 R14: ffff888152eb0210 R15: ffffc900017e3ed8
> > [ 482.154554][ T699] FS: 00007fa60d4fdd00(0000) GS:ffff88846d200000(0000) knlGS:0000000000000000
> > [ 482.155138][ T699] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > [ 482.155564][ T699] CR2: 00007fa60d7d8000 CR3: 00000001502a2005 CR4: 0000000000770ef0
> > [ 482.156095][ T699] PKRU: 55555554
> > [ 482.156349][ T699] Call Trace:
> > [ 482.156596][ T699] <TASK>
> > [ 482.156816][ T699] ? __die_body+0x68/0xb0
> > [ 482.157138][ T699] ? die+0xba/0xe0
> > [ 482.157456][ T699] ? do_trap+0xa5/0x180
> > [ 482.157826][ T699] ? bpf_for_each_array_elem+0xbb/0x120
> > [ 482.158277][ T699] ? bpf_for_each_array_elem+0xbb/0x120
> > [ 482.158711][ T699] ? do_error_trap+0xc4/0x140
> > [ 482.159052][ T699] ? bpf_for_each_array_elem+0xbb/0x120
> > [ 482.159506][ T699] ? handle_invalid_op+0x2c/0x40
> > [ 482.159906][ T699] ? bpf_for_each_array_elem+0xbb/0x120
> > [ 482.160990][ T699] ? exc_invalid_op+0x38/0x60
> > [ 482.161375][ T699] ? asm_exc_invalid_op+0x1a/0x20
> > [ 482.161788][ T699] ? 0xffffffffa0012774
> > [ 482.162149][ T699] ? 0xffffffffa0012774
> > [ 482.162513][ T699] ? bpf_for_each_array_elem+0xbb/0x120
> > [ 482.162905][ T699] bpf_prog_ca45ea7f9cb8ac1a_inner_map+0x94/0x98
> > [ 482.163471][ T699] bpf_trampoline_6442549234+0x47/0x1000
>
> Looks like this trips an #UD, I'll go try and figure out what this
> bpf_for_each_array_elem() does to cause this. Looks like it has an
> indirect call, could be the callback_fn thing has a CFI mis-match.
So afaict this is used through bpf_for_each_map_elem(), where the
argument still is properly callback_fn. However, in the desriptor
bpf_for_each_map_elem_proto the argument gets described as:
ARG_PTR_TO_FUNC, which in turn has a comment like:
ARG_PTR_TO_FUNC, /* pointer to a bpf program function */
Which to me sounds like there is definite type punning involved. The
call in bpf_for_each_array_elem() is a regular C indirect call, which
gets adorned with the kCFI magic.
But I doubt the BPF function that gets used gets the correct matching
bits on.
TL;DR, I think this is a pre-existing problem with kCFI + eBPF and not
caused by my patches.
Could any of you bpf knowledgeable folks please explain me exactly what
gets used as the function pointer in this case? -- I'm not sure I can
follow along well enough to begin looking for a solution at this point
:/
next prev parent reply other threads:[~2023-12-04 18:34 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-30 13:36 [PATCH v2 0/2] x86/bpf: Fix FineIBT vs eBPF Peter Zijlstra
2023-11-30 13:36 ` [PATCH v2 1/2] cfi: Flip headers Peter Zijlstra
2023-12-04 19:18 ` Sami Tolvanen
2023-11-30 13:36 ` [PATCH v2 2/2] x86/cfi,bpf: Fix BPF JIT call Peter Zijlstra
2023-12-03 22:56 ` Alexei Starovoitov
2023-12-04 9:13 ` Peter Zijlstra
2023-12-04 11:11 ` Peter Zijlstra
2023-12-04 12:52 ` Peter Zijlstra
2023-12-04 17:25 ` Jiri Olsa
2023-12-04 18:16 ` Peter Zijlstra
2023-12-04 18:33 ` Peter Zijlstra [this message]
2023-12-04 18:58 ` Sami Tolvanen
2023-12-05 1:18 ` Alexei Starovoitov
2023-12-06 15:35 ` Peter Zijlstra
2023-12-06 16:38 ` Peter Zijlstra
2023-12-06 18:37 ` Peter Zijlstra
2023-12-06 21:39 ` Alexei Starovoitov
2023-12-07 9:31 ` Peter Zijlstra
2023-12-07 22:32 ` Alexei Starovoitov
2023-12-08 10:29 ` Peter Zijlstra
2023-12-08 13:40 ` Peter Zijlstra
2023-12-08 17:21 ` Peter Zijlstra
2023-12-08 19:40 ` Alexei Starovoitov
2023-12-08 20:27 ` Peter Zijlstra
2023-12-08 20:35 ` Peter Zijlstra
2023-12-08 20:41 ` Alexei Starovoitov
2023-12-08 20:52 ` Peter Zijlstra
2023-12-08 20:58 ` Alexei Starovoitov
2023-12-08 22:45 ` Peter Zijlstra
2023-12-09 4:51 ` Alexei Starovoitov
2023-12-08 19:32 ` Alexei Starovoitov
2023-12-08 20:18 ` Peter Zijlstra
2023-12-08 20:45 ` Alexei Starovoitov
2023-12-08 20:56 ` Peter Zijlstra
2023-12-08 21:04 ` Alexei Starovoitov
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