netdev - Re: [PATCH v2 2/2] x86/cfi,bpf: Fix BPF JIT call

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date: Fri, 8 Dec 2023 20:51:27 -0800
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Jiri Olsa <olsajiri@...il.com>, Song Liu <song@...nel.org>, 
	Song Liu <songliubraving@...a.com>, Paul Walmsley <paul.walmsley@...ive.com>, 
	Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, X86 ML <x86@...nel.org>, 
	"H. Peter Anvin" <hpa@...or.com>, "David S. Miller" <davem@...emloft.net>, David Ahern <dsahern@...nel.org>, 
	Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, 
	Yonghong Song <yonghong.song@...ux.dev>, John Fastabend <john.fastabend@...il.com>, 
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...gle.com>, Hao Luo <haoluo@...gle.com>, 
	Arnd Bergmann <arnd@...db.de>, Sami Tolvanen <samitolvanen@...gle.com>, 
	Kees Cook <keescook@...omium.org>, Nathan Chancellor <nathan@...nel.org>, 
	Nick Desaulniers <ndesaulniers@...gle.com>, linux-riscv <linux-riscv@...ts.infradead.org>, 
	LKML <linux-kernel@...r.kernel.org>, Network Development <netdev@...r.kernel.org>, 
	bpf <bpf@...r.kernel.org>, linux-arch <linux-arch@...r.kernel.org>, 
	clang-built-linux <llvm@...ts.linux.dev>, Josh Poimboeuf <jpoimboe@...nel.org>, 
	Joao Moreira <joao@...rdrivepizza.com>, Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH v2 2/2] x86/cfi,bpf: Fix BPF JIT call

On Fri, Dec 8, 2023 at 2:46 PM Peter Zijlstra <peterz@...radead.org> wrote:
>
>
> Ok, did that. Current patches (on top of bpf-next) are here:
>
>   git://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git x86/cfi

Looks really great. The last patch is cleaner than I expected. Good idea.

> (really should try and write better changelogs, but it's too late)

commit logs look fine except the "pilfer" word that I had to look up
in the dictionary :)

> [  247.721063]  ? bpf_throw+0x9b/0xf0
> [  247.721126]  ? bpf_test_run+0x108/0x350
> [  247.721191]  ? bpf_prog_5555714b685bf0cf_exception_throw_always_1+0x26/0x26
> [  247.721301]  ? bpf_test_run+0x108/0x350
> [  247.721368]  bpf_test_run+0x212/0x350
> [  247.721433]  ? slab_build_skb+0x22/0x110
> [  247.721503]  bpf_prog_test_run_skb+0x347/0x4a0
>
> But I'm too tired to think staight. Is  this a bpf_callback_t vs
> bpf_exception_cb difference?

Yep.
It's easy to fix:
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 0e162eae8639..e36b3f41751e 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1484,7 +1484,7 @@ struct bpf_prog_aux {
        int cgroup_atype; /* enum cgroup_bpf_attach_type */
        struct bpf_map *cgroup_storage[MAX_BPF_CGROUP_STORAGE_TYPE];
        char name[BPF_OBJ_NAME_LEN];
-       unsigned int (*bpf_exception_cb)(u64 cookie, u64 sp, u64 bp);
+       u64 (*bpf_exception_cb)(u64 cookie, u64 sp, u64 bp, u64, u64);
 #ifdef CONFIG_SECURITY
        void *security;
 #endif
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index fe229b28e4a9..650ebe8ff183 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2537,7 +2537,7 @@ __bpf_kfunc void bpf_throw(u64 cookie)
         * which skips compiler generated instrumentation to do the same.
         */
        kasan_unpoison_task_stack_below((void *)(long)ctx.sp);
-       ctx.aux->bpf_exception_cb(cookie, ctx.sp, ctx.bp);
+       ctx.aux->bpf_exception_cb(cookie, ctx.sp, ctx.bp, 0, 0);
        WARN(1, "A call to BPF exception callback should never return\n");
 }

and with that all of test_progs runs successfully without CFI panics.
*happy dance*

Only test_progs -t btf/line_info fails suspiciously.
There we check that line info embedded in the prog looks sane.
New cfi preamble is probably tripping something.
It could be a test issue. I'll investigate. It's not a blocker.

Do you mind resending the whole set so that BPF CI can test it
on different archs ?