From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3B579C433EF for ; Fri, 6 May 2022 17:42:16 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9E2826B0071; Fri, 6 May 2022 13:42:15 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9936A6B0073; Fri, 6 May 2022 13:42:15 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7E5CC6B0074; Fri, 6 May 2022 13:42:15 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 6AB8F6B0071 for ; Fri, 6 May 2022 13:42:15 -0400 (EDT) Received: from smtpin15.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay12.hostedemail.com (Postfix) with ESMTP id 33736121C66 for ; Fri, 6 May 2022 17:42:15 +0000 (UTC) X-FDA: 79436037030.15.B0A49C2 Received: from mail-yb1-f181.google.com (mail-yb1-f181.google.com [209.85.219.181]) by imf20.hostedemail.com (Postfix) with ESMTP id 7A5541C001E for ; Fri, 6 May 2022 17:42:07 +0000 (UTC) Received: by mail-yb1-f181.google.com with SMTP id g28so14083396ybj.10 for ; Fri, 06 May 2022 10:42:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=YKfnJFHuOviCdMg0UB5UffT9B/WVcObEOxiRN5y2Kug=; b=emmUN3k1bPN4J6n6aBe2FemprgUT+FF6VAYxV6ekMwnHvd4yMg9T5KGYmUYmFa9oAe l8wgj8tdCP2FJPIShfAg2Fk/rOBVcSKoqvKeqjnUKen1LIajvaEdZt/TPfqzH6t/XrSo syM1kjCv3gSDfacEuEc3EgG0lwGjeC2hWNg5U2El7kqEz+o0tsjk8MjpqNijR6o+XqPs q3onvlApQgHZ5xOXxhHzjSgk18UOnvT+GgtT76x6XFC/llE4jgVQddy0F0CFkFJAkHTB 0S9hvZkV7X0lPAIZLLytf/7qjnZXN3mz9RqswI5f966807Geg/q/71UbscP2MlkhGUSo 7bxw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=YKfnJFHuOviCdMg0UB5UffT9B/WVcObEOxiRN5y2Kug=; b=5jaT9NMBMwBMQKABU8NfCXl81fisYUXS+7HwjlfXtXcG72yEbVhvO5UFLK/x68VfGI nuGX2BcHzPJ5CNY4nzS5XPDgSFRDr+fbWj4iBlTpWMnpsXHGzhH/Op44JXQat6w4e5fI Q0HYXtBq97mD8/Wa5yHWwU1kwyBJmHDOF1q5aBqe3fNxt1Q8NPlZJpkABNI2hBAtNiES Lab1aPt+XGGDRQOiwx7o4rB5zXCxw5HpR8qy//ccFcTYgZk9BPvvgyjeJ5478Xmyhy69 2/qyIDzobQAfFsld2vDwjW14qkww9/2kESVQJnGjvv4KEHZA/gr/THux3q+rQwGr0AHs qYhg== X-Gm-Message-State: AOAM5300K6dGPswErNTyFFNjrjzcneG37lOqb9VDife6+A5qgsB8ryxR zvphA5FQkcw5OCEtB8ObODddN6Yw3GZeFm5Ul5JbEw== X-Google-Smtp-Source: ABdhPJws5njwDWJ9xDpRYMne8cwuzMbwVAp2MzFRAKHvjVIKPSom5y1drK/dJlbHrWExYpCexhrZLlT5LtJ6/fdqUbo= X-Received: by 2002:a25:bb0f:0:b0:61d:60f9:aaf9 with SMTP id z15-20020a25bb0f000000b0061d60f9aaf9mr3038082ybg.199.1651858933696; Fri, 06 May 2022 10:42:13 -0700 (PDT) MIME-Version: 1.0 References: <20220426164315.625149-1-glider@google.com> <20220426164315.625149-29-glider@google.com> <87a6c6y7mg.ffs@tglx> <87y1zjlhmj.ffs@tglx> <878rrfiqyr.ffs@tglx> <87k0ayhc43.ffs@tglx> In-Reply-To: <87k0ayhc43.ffs@tglx> From: Alexander Potapenko Date: Fri, 6 May 2022 19:41:37 +0200 Message-ID: Subject: Re: [PATCH v3 28/46] kmsan: entry: handle register passing from uninstrumented code To: Thomas Gleixner Cc: Alexander Viro , Andrew Morton , Andrey Konovalov , Andy Lutomirski , Arnd Bergmann , Borislav Petkov , Christoph Hellwig , Christoph Lameter , David Rientjes , Dmitry Vyukov , Eric Dumazet , Greg Kroah-Hartman , Herbert Xu , Ilya Leoshkevich , Ingo Molnar , Jens Axboe , Joonsoo Kim , Kees Cook , Marco Elver , Mark Rutland , Matthew Wilcox , "Michael S. Tsirkin" , Pekka Enberg , Peter Zijlstra , Petr Mladek , Steven Rostedt , Vasily Gorbik , Vegard Nossum , Vlastimil Babka , kasan-dev , Linux Memory Management List , Linux-Arch , LKML Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 7A5541C001E X-Stat-Signature: j8z4kjfh7z937tefrh7jntmnmg9ngpb5 X-Rspam-User: Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=emmUN3k1; spf=pass (imf20.hostedemail.com: domain of glider@google.com designates 209.85.219.181 as permitted sender) smtp.mailfrom=glider@google.com; dmarc=pass (policy=reject) header.from=google.com X-HE-Tag: 1651858927-893580 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 Fri, May 6, 2022 at 6:14 PM Thomas Gleixner wrote: > > On Fri, May 06 2022 at 16:52, Alexander Potapenko wrote: > > On Thu, May 5, 2022 at 11:56 PM Thomas Gleixner wrote: > >> @@ -452,6 +455,7 @@ irqentry_state_t noinstr irqentry_nmi_en > >> rcu_nmi_enter(); > >> > >> instrumentation_begin(); > >> + unpoison(regs); > >> trace_hardirqs_off_finish(); > >> ftrace_nmi_enter(); > >> instrumentation_end(); > >> > >> As I said: 4 places :) > > > > These four instances still do not look sufficient. > > Right now I am seeing e.g. reports with the following stack trace: > > > > BUG: KMSAN: uninit-value in irqtime_account_process_tick+0x255/0x580 > > kernel/sched/cputime.c:382 > > irqtime_account_process_tick+0x255/0x580 kernel/sched/cputime.c:382 > > account_process_tick+0x98/0x450 kernel/sched/cputime.c:476 > > update_process_times+0xe4/0x3e0 kernel/time/timer.c:1786 > > tick_sched_handle kernel/time/tick-sched.c:243 > > tick_sched_timer+0x83e/0x9e0 kernel/time/tick-sched.c:1473 > > __run_hrtimer+0x518/0xe50 kernel/time/hrtimer.c:1685 > > __hrtimer_run_queues kernel/time/hrtimer.c:1749 > > hrtimer_interrupt+0x838/0x15a0 kernel/time/hrtimer.c:1811 > > local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1086 > > __sysvec_apic_timer_interrupt+0x1ae/0x680 arch/x86/kernel/apic/apic.c:1103 > > sysvec_apic_timer_interrupt+0x95/0xc0 arch/x86/kernel/apic/apic.c:1097 > > ... > > (uninit creation stack trace is irrelevant here, because it is some > > random value from the stack) > > > > sysvec_apic_timer_interrupt() receives struct pt_regs from > > uninstrumented code, so regs can be partially uninitialized. > > They are not passed down the call stack directly, but are instead > > saved by set_irq_regs() in sysvec_apic_timer_interrupt() and loaded by > > get_irq_regs() in tick_sched_timer(). > > sysvec_apic_timer_interrupt() invokes irqentry_enter() _before_ > set_irq_regs() and irqentry_enter() unpoisons @reg. > > Confused... As far as I can tell in this case sysvect_apic_timer_interrupt() is called by the following code in arch/x86/kernel/idt.c: INTG(LOCAL_TIMER_VECTOR, asm_sysvec_apic_timer_interrupt), , which does not use IDTENTRY_SYSVEC framework and thus does not call irqentry_enter(). I guess handling those will require wrapping every interrupt gate into a function that performs register unpoisoning? By the way, if it helps, I think we don't necessarily have to call kmsan_unpoison_memory() from within the instrumentation_begin()/instrumentation_end() region? We could move the call to the beginning of irqentry_enter(), removing unnecessary duplication.