From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from dggsgout11.his.huawei.com (dggsgout11.his.huawei.com [45.249.212.51]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BC87D2C859 for ; Sat, 30 Aug 2025 01:35:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.51 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756517706; cv=none; b=dduX5FAP+SctnIPdMqw3oyi/eD6GPb7TnvVm3oLMJ8GR4iJyNNyqNw+vJ/m+l4nLvX6Q2OWx7cH7wLhbXqbg0sbbglE0/6FObpsQzNjMiHEPaaYsJ1s91iinqVMWU8bb9AZIzIx6Wyq7p7OdOjX+FNMMt9rIBvTeZb00Gu10Y6M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756517706; c=relaxed/simple; bh=ijzvWh0TzEH7u5xs/tSn46YbO9xaLfMw5bheNAK5N0s=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=HxqJfP7UU6ezPU6ErzoLcfXROTmdQquvhArP/2t3rBwbo37/OluSZJpRFFWHijJlXhOUQ0h0uCtiughlNvbCYM6RJgzQK3TCXgSjKZG89dxRqstV4ZSFxXKA1yD0nA7czZsTmp7WXXuHrwXB4Pa7+bQSocAUR7iVOZpc6FwG9fo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com; spf=pass smtp.mailfrom=huaweicloud.com; arc=none smtp.client-ip=45.249.212.51 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huaweicloud.com Received: from mail.maildlp.com (unknown [172.19.163.216]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTPS id 4cDHkZ214fzYQtvj for ; Sat, 30 Aug 2025 09:35:02 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.75]) by mail.maildlp.com (Postfix) with ESMTP id C87341A1747 for ; Sat, 30 Aug 2025 09:35:00 +0800 (CST) Received: from [10.67.110.36] (unknown [10.67.110.36]) by APP2 (Coremail) with SMTP id Syh0CgD3IZlDVbJojej+Ag--.6253S2; Sat, 30 Aug 2025 09:35:00 +0800 (CST) Message-ID: Date: Sat, 30 Aug 2025 09:34:59 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH -next v2] x86: Prevent KASAN false positive warnings in __show_regs To: Josh Poimboeuf Cc: x86@kernel.org, Andrey Ryabinin , Dave Hansen , Thomas Gleixner , Alexander Potapenko , Andrey Konovalov , Borislav Petkov , Dmitry Vyukov , Ingo Molnar , linux-kernel@vger.kernel.org References: <20250829094744.3133324-1-wutengda@huaweicloud.com> Content-Language: en-US From: Tengda Wu In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CM-TRANSID:Syh0CgD3IZlDVbJojej+Ag--.6253S2 X-Coremail-Antispam: 1UD129KBjvdXoWrtr18WFy5Xw1UZF13KFyDWrg_yoWkuFb_W3 yvvFWqkr43AFs3Aw1DWw4UXry7Ww45Gws3JF48KFWjqrykJrWkJrZYyF93Ary7Xw1jvFnx Cw1Dt34ak39F9jkaLaAFLSUrUUUUjb8apTn2vfkv8UJUUUU8Yxn0WfASr-VFAUDa7-sFnT 9fnUUIcSsGvfJTRUUUbxxYFVCjjxCrM7AC8VAFwI0_Gr0_Xr1l1xkIjI8I6I8E6xAIw20E Y4v20xvaj40_Wr0E3s1l1IIY67AEw4v_Jr0_Jr4l8cAvFVAK0II2c7xJM28CjxkF64kEwV A0rcxSw2x7M28EF7xvwVC0I7IYx2IY67AKxVWDJVCq3wA2z4x0Y4vE2Ix0cI8IcVCY1x02 67AKxVW8Jr0_Cr1UM28EF7xvwVC2z280aVAFwI0_GcCE3s1l84ACjcxK6I8E87Iv6xkF7I 0E14v26rxl6s0DM2AIxVAIcxkEcVAq07x20xvEncxIr21l5I8CrVACY4xI64kE6c02F40E x7xfMcIj6xIIjxv20xvE14v26r1j6r18McIj6I8E87Iv67AKxVWUJVW8JwAm72CE4IkC6x 0Yz7v_Jr0_Gr1lF7xvr2IY64vIr41lFIxGxcIEc7CjxVA2Y2ka0xkIwI1lc7CjxVAaw2AF wI0_Jw0_GFyl42xK82IYc2Ij64vIr41l4I8I3I0E4IkC6x0Yz7v_Jr0_Gr1lx2IqxVAqx4 xG67AKxVWUJVWUGwC20s026x8GjcxK67AKxVWUGVWUWwC2zVAF1VAY17CE14v26r1q6r43 MIIYrxkI7VAKI48JMIIF0xvE2Ix0cI8IcVAFwI0_Jr0_JF4lIxAIcVC0I7IYx2IY6xkF7I 0E14v26r4j6F4UMIIF0xvE42xK8VAvwI8IcIk0rVWUJVWUCwCI42IY6I8E87Iv67AKxVWU JVW8JwCI42IY6I8E87Iv6xkF7I0E14v26r4j6r4UJbIYCTnIWIevJa73UjIFyTuYvjxUF1 v3UUUUU X-CM-SenderInfo: pzxwv0hjgdqx5xdzvxpfor3voofrz/ On 2025/8/30 5:01, Josh Poimboeuf wrote: > On Fri, Aug 29, 2025 at 09:47:44AM +0000, Tengda Wu wrote: >> static void show_regs_if_on_stack(struct stack_info *info, struct pt_regs *regs, >> bool partial, const char *log_lvl) >> { >> + bool kasan_disabled = false; >> + >> + /* >> + * When 'regs' resides in another task's stack space, KASAN should be >> + * disabled to prevent false positives during 'regs->' operation, as >> + * the 'regs' contents may change concurrently with task execution. >> + */ >> + if (!object_is_on_stack(regs)) { >> + kasan_disable_current(); >> + kasan_disabled = true; >> + } > > I don't think this is right. object_is_on_stack() only checks current's > *task* stack. However the regs might be on a different stack used by > current (e.g., exception stack). In which case there's no need to > disable KASAN. > > What really determines the KASAN-safety is whether it's the current task > or not. > I see. Since operations walking other tasks' regs-> only occur in show_regs_if_on_stack, to cover a more accurate range and targets, it seems we have no choice but to add a task parameter to show_regs_if_on_stack and then perform the check, right?