linux-kernel - Re: [RFC PATCH bpf-next 1/2] bpf, x64: Fix tailcall infinite loop bug

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

Message-ID: <841306f0691a7d56be72be0bb3c7472eadcc3367.camel@gmail.com>
Date:   Tue, 15 Aug 2023 17:35:50 +0300
From:   Eduard Zingerman <eddyz87@...il.com>
To:     Leon Hwang <hffilwlqm@...il.com>, bpf@...r.kernel.org
Cc:     ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
        martin.lau@...ux.dev, song@...nel.org, yonghong.song@...ux.dev,
        john.fastabend@...il.com, kpsingh@...nel.org, sdf@...gle.com,
        haoluo@...gle.com, jolsa@...nel.org, x86@...nel.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, hpa@...or.com, mykolal@...com,
        shuah@...nel.org, davem@...emloft.net, dsahern@...nel.org,
        tangyeechou@...il.com, kernel-patches-bot@...com,
        maciej.fijalkowski@...el.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [RFC PATCH bpf-next 1/2] bpf, x64: Fix tailcall infinite loop
 bug

On Tue, 2023-08-15 at 11:01 +0800, Leon Hwang wrote:
[...]
> a) Initial value of RAX is in emit_prologue().
> 	if (!ebpf_from_cbpf) {
> 		if (tail_call_reachable && !is_subprog)
> 			/* When it's the entry of the whole
> 			 * tailcall context, zeroing the RAX
> 			 * means init tail_call_cnt.
> 			 */
> 			EMIT2(0x31, 0xC0); /* xor eax, eax */
> 		else
> 			// Keep the same asm layout.
> 			EMIT2(0x66, 0x90); /* nop2 */
> 	}
>    I'd like to add this comment to emit_prologue().

Got it, thank you.


[...]