linux-kernel - Re: [PATCH] ptrace/x86: introduce TS_COMPAT_RESTART to fix get_nr_restart

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]

Date:   Fri, 29 Nov 2019 18:32:13 +0100
From:   Oleg Nesterov <oleg@...hat.com>
To:     Andy Lutomirski <luto@...capital.net>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...nel.org>,
        Jan Kratochvil <jan.kratochvil@...hat.com>,
        Pedro Alves <palves@...hat.com>, Peter Anvin <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        the arch/x86 maintainers <x86@...nel.org>
Subject: Re: [PATCH] ptrace/x86: introduce TS_COMPAT_RESTART to fix
 get_nr_restart_syscall()

On 11/28, Andy Lutomirski wrote:
>
> I think this doesn’t work for x32.

Why? get_nr_restart_syscall() can still rely on the "orig_ax & __X32_SYSCALL_BIT"
check, debugger should restore regs->orig_ax correctly.

> Let’s either save the result of syscall_get_arch()

We can save the result of syscall_get_arch(), but it doesn't distinguish
x32/x86_64 tasks, so it doesn't really differ from TS_COMPAT.

> or just actually calculate and save the restart_syscall nr here.

sure, we we can do this.

> Before we commit to this, Kees, do you think we can manage to just renumber
> restart_syscall()?  That’s a much better solution if we can pull it off.

Agreed.

Oleg.