linux-kernel - Re: [PATCH v2 -tip] x86/percpu: Use C for arch_raw_cpu

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: <10930088-3B4E-4BED-896C-CA66AB196010@vmware.com>
Date:   Tue, 17 Oct 2023 22:06:51 +0000
From:   Nadav Amit <namit@...are.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
CC:     Uros Bizjak <ubizjak@...il.com>,
        the arch/x86 maintainers <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Brian Gerst <brgerst@...il.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: Re: [PATCH v2 -tip] x86/percpu: Use C for arch_raw_cpu_ptr()



> On Oct 18, 2023, at 12:53 AM, Linus Torvalds <torvalds@...ux-foundation.org> wrote:
> 
> 
> but none of this should even matter, because by the time we actually
> *schedule* that thread, we'll set active_mm to the right thing.
> 
> Can anybody see what's up?

Could it be related to exec_mmap() -> exec_mm_release() -> mm_release() -> deactivate_mm() ?

#define deactivate_mm(tsk, mm)                  \
do {                                            \
        if (!tsk->vfork_done)                   \
                shstk_free(tsk);                \
        load_gs_index(0);                       \
        loadsegment(fs, 0);                     \
} while (0)

We change gs_index(), so perhaps it affects later GS reads. There is also this
X86_BUG_NULL_SEG. Need to dive deeper; just initial thoughts though (i.e., I might be
completely off).