linux-kernel - Re: [RFC PATCH v2 03/15] x86/unwind_user: Guard unwind_user_word_size() by UNWIND

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: <CAHk-=wh4_BPvniQZqvEQ4cCC3WfvQqruWk0b1Yek+0d5S1LuxQ@mail.gmail.com>
Date: Fri, 5 Dec 2025 09:23:54 -0800
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Jens Remus <jremus@...ux.ibm.com>
Cc: linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org, 
	linux-s390@...r.kernel.org, bpf@...r.kernel.org, x86@...nel.org, 
	Steven Rostedt <rostedt@...nel.org>, Heiko Carstens <hca@...ux.ibm.com>, 
	Vasily Gorbik <gor@...ux.ibm.com>, Ilya Leoshkevich <iii@...ux.ibm.com>, 
	Josh Poimboeuf <jpoimboe@...nel.org>, Masami Hiramatsu <mhiramat@...nel.org>, 
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Peter Zijlstra <peterz@...radead.org>, 
	Ingo Molnar <mingo@...nel.org>, Jiri Olsa <jolsa@...nel.org>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Thomas Gleixner <tglx@...utronix.de>, Andrii Nakryiko <andrii@...nel.org>, 
	Indu Bhagat <indu.bhagat@...cle.com>, "Jose E. Marchesi" <jemarch@....org>, 
	Beau Belgrave <beaub@...ux.microsoft.com>, Andrew Morton <akpm@...ux-foundation.org>, 
	Florian Weimer <fweimer@...hat.com>, Kees Cook <kees@...nel.org>, 
	"Carlos O'Donell" <codonell@...hat.com>, Sam James <sam@...too.org>, 
	Dylan Hatch <dylanbhatch@...gle.com>
Subject: Re: [RFC PATCH v2 03/15] x86/unwind_user: Guard unwind_user_word_size()
 by UNWIND_USER

 Random nit...

On Fri, 5 Dec 2025 at 09:15, Jens Remus <jremus@...ux.ibm.com> wrote:
>
> +static inline int unwind_user_word_size(struct pt_regs *regs)
> +{
> +       /* We can't unwind VM86 stacks */
> +       if (regs->flags & X86_VM_MASK)
> +               return 0;
> +#ifdef CONFIG_X86_64
> +       if (!user_64bit_mode(regs))
> +               return sizeof(int);
> +#endif
> +       return sizeof(long);
> +}

I realize you just moved this around, but since I see it in the patch,
the #ifdef annoys me.

That user_64bit_mode() should work equally well on 32-bit, and this
can be written as

        return user_64bit_mode(regs) ? 8 : 4;

which avoids the #ifdef, and makes a lot more sense ("sizeof(long)"
together with "user_64bit_mode()"? It's literally testing 32 vs 64
bitness, not "int vs long").

              Linus