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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E4776C4332F for ; Tue, 8 Nov 2022 09:02:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233603AbiKHJCd (ORCPT ); Tue, 8 Nov 2022 04:02:33 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58346 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232958AbiKHJCb (ORCPT ); Tue, 8 Nov 2022 04:02:31 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0CF4013D2B for ; Tue, 8 Nov 2022 01:02:30 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id AF49AB819BA for ; Tue, 8 Nov 2022 09:02:28 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id F38E7C433C1; Tue, 8 Nov 2022 09:02:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1667898147; bh=40as9zy58r8i/rJfR7Z6TRRJsKNmmDmW8cmLv1ORktE=; h=From:To:Cc:Subject:Date:From; b=pkfJDph7m26p588lRvKtcu20kjCZlELls26LoNAh2HMA5oPn4okhu+02A9B5HV3wA B6jM2Tx5CPm9N/P5lhalCJiQt42kptl2J5hRuWT6HjMUqjW08sO3Em22n0jZyCU3gJ 3y9HFKaL+e090LM91K1PI1j8enY9F0ucXaXMlQ25o6WheVnYeHLtcWhY9C7SyVvLV3 T5jrQqwTCPLZXTF3Ul4a7NHJKrq3Wu5wN/ILrFsxine91hKQh6vZkmLS5IKP41nWYk 0BcrifcoSpgRNaQ4cHm2cr3ey405LJ8I60X1f5QlJcKSat60uEUcgeT/9qfz17kjmd 95rwf8jqrAZfA== From: guoren@kernel.org To: anup@brainfault.org, paul.walmsley@sifive.com, palmer@dabbelt.com, alexandre.ghiti@canonical.com, conor.dooley@microchip.com, heiko@sntech.de, philipp.tomsich@vrull.eu Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, Guo Ren , Guo Ren , Anup Patel , Palmer Dabbelt Subject: [PATCH] riscv: asid: Fixup stale TLB entry cause application crash Date: Tue, 8 Nov 2022 04:02:19 -0500 Message-Id: <20221108090219.3285030-1-guoren@kernel.org> X-Mailer: git-send-email 2.36.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Guo Ren When use_asid_allocator is enabled, the userspace application would crash by stale tlb entry. Because only using cpumask_clear_cpu without local_flush_tlb_all couldn't guarantee CPU's tlb contains fresh mapping entry. Then set_mm_asid would cause user space application get a stale value by stale tlb entry, but set_mm_noasid is okay. Here is the symptom of the bug: unhandled signal 11 code 0x1 (coredump) 0x0000003fd6d22524 <+4>: auipc s0,0x70 0x0000003fd6d22528 <+8>: ld s0,-148(s0) # 0x3fd6d92490 => 0x0000003fd6d2252c <+12>: ld a5,0(s0) (gdb) i r s0 s0 0x8082ed1cc3198b21 0x8082ed1cc3198b21 (gdb) x/16 0x3fd6d92490 0x3fd6d92490: 0xd80ac8a8 0x0000003f The core dump file show us the value of register s0 is wrong, but the value in memory is right. When task run on CPU0, the task loaded/speculative-loaded the value of address-0x3fd6d92490, the first version tlb mapping enter in CPU0's tlb. When the task switched from CPU0 to CPU1 without local_tlb_flush_all (because of asid), the task happened to write a value on address: 0x3fd6d92490 that caused do_page_fault -> wp_page_copy -> ptep_clear_flush -> ptep_get_and_clear & flush_tlb_page. The flush_tlb_page would use mm_cpumask(mm) to determine which CPUs need tlb flush, but CPU0 cleared the CPU0's mm_cpumask in previous switch_mm. So we only flushed the CPU1's tlb entry, and setted second version mapping of the pte. When the task switch from CPU1 to CPU0 again, it still used a stale tlb entry on CPU0 which contained a wrong target physical address. When the task happened to read that value, the bug would be raised. Fixes: 65d4b9c53017 ("RISC-V: Implement ASID allocator") Signed-off-by: Guo Ren Signed-off-by: Guo Ren Cc: Anup Patel Cc: Palmer Dabbelt --- arch/riscv/mm/context.c | 1 - 1 file changed, 1 deletion(-) diff --git a/arch/riscv/mm/context.c b/arch/riscv/mm/context.c index 7acbfbd14557..843e86b63532 100644 --- a/arch/riscv/mm/context.c +++ b/arch/riscv/mm/context.c @@ -317,7 +317,6 @@ void switch_mm(struct mm_struct *prev, struct mm_struct *next, */ cpu = smp_processor_id(); - cpumask_clear_cpu(cpu, mm_cpumask(prev)); cpumask_set_cpu(cpu, mm_cpumask(next)); set_mm(next, cpu); -- 2.36.1