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[209.85.167.50]) by smtp.gmail.com with ESMTPSA id w26sm485014ljm.11.2020.10.22.17.30.38 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 22 Oct 2020 17:30:38 -0700 (PDT) Received: by mail-lf1-f50.google.com with SMTP id a7so4467000lfk.9 for ; Thu, 22 Oct 2020 17:30:38 -0700 (PDT) X-Received: by 2002:a05:651c:503:: with SMTP id o3mr1747084ljp.421.1603412592176; Thu, 22 Oct 2020 17:23:12 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Linus Torvalds Date: Thu, 22 Oct 2020 17:22:56 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: mmstress[1309]: segfault at 7f3d71a36ee8 ip 00007f3d77132bdf sp 00007f3d71a36ee8 error 4 in libc-2.27.so[7f3d77058000+1aa000] To: Naresh Kamboju Cc: open list , linux-m68k , X86 ML , LTP List , lkft-triage@lists.linaro.org, Linux-Next Mailing List , linux-mm , kasan-dev , Christian Brauner , Ingo Molnar , Thomas Gleixner , "Matthew Wilcox (Oracle)" , "Peter Zijlstra (Intel)" , Al Viro , Geert Uytterhoeven , Viresh Kumar , zenglg.jy@cn.fujitsu.com, Stephen Rothwell , "Eric W. Biederman" , Dmitry Vyukov Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Oct 22, 2020 at 5:11 PM Linus Torvalds wrote: > > In particular, I wonder if it's that KASAN causes some reload pattern, > and the whole > > register __typeof__(*(ptr)) __val_pu asm("%"_ASM_AX); > .. > asm volatile(.. "r" (__val_pu) ..) > > thing causes problems. That pattern isn't new (see the same pattern and the comment above get_user). But our previous use of that pattern had it as an output of the asm, and the new use is as an input. That obviously shouldn't matter, but if it's some odd compiler code generation interaction, all bets are off.. Linus