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Sat, 29 Nov 2025 18:03:41 +0800 (CST) Received: from kwepemj100009.china.huawei.com (unknown [7.202.194.3]) by mail.maildlp.com (Postfix) with ESMTPS id D16C8180B4E; Sat, 29 Nov 2025 18:06:01 +0800 (CST) Received: from DESKTOP-A37P9LK.huawei.com (10.67.109.17) by kwepemj100009.china.huawei.com (7.202.194.3) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Sat, 29 Nov 2025 18:06:00 +0800 From: Xie Yuanbin To: CC: , , , , , , , , , , , , , , , , , , , , Subject: Re: [Bug report] hash_name() may cross page boundary and trigger Date: Sat, 29 Nov 2025 18:05:57 +0800 Message-ID: <20251129100557.10610-1-xieyuanbin1@huawei.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251129094448.GL3538@ZenIV> References: <20251129094448.GL3538@ZenIV> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Originating-IP: [10.67.109.17] X-ClientProxiedBy: kwepems200001.china.huawei.com (7.221.188.67) To kwepemj100009.china.huawei.com (7.202.194.3) X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 3660EC000D X-Stat-Signature: 5ji8exnbcgmwyq6o534nuth819y53e17 X-Rspam-User: X-HE-Tag: 1764410767-560464 X-HE-Meta: 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 XiNtU/mg SGcuh9GlmHYco/MXoy6u3Q3tnqbkgq03GujSsH7KP/UPQ9Jj1ytufmYdGItN7tjv0CGj2MYDpdZW99Z0kByLN7Kiw1ib5OPVNH+NY9IkqkYsrX8QPSOrv+PRmLqsBza++g/7SRfX+Gl4/95QjHnGHFigkdjG+1BrqpkngNNHl8dFal08FMTbIrMP8+Migkw6AjiEpmYnZtzQDS2IYO/mIxbhmeYuYkfh8oT/qCvxhuXHBsN82eZy5SrUY3q0QqaD5nC+jNVY6LkMXXPxpcMnNDSUOGq2IpnRcu9tKUe6taGdefxMDg9y2U64wAZBYMxBtaJJKP0Van4wVn4qrkNNmBcDsuKM2TWGsCWf7QDd9FVM00S5+X2grRwjRmND+LD/4JbuSudqqOyNNy5tNJVoyT991IenrMUdt8M1sjXV7Api4ch+4fAn0SoOyCIWZlNsGvuFXPofGNTRUX3mPf3eO3lT/VA== 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: List-Subscribe: List-Unsubscribe: On Sat, 29 Nov 2025 09:44:48 +0000, Al Viro wrote: > On Sat, Nov 29, 2025 at 05:25:45PM +0800, Xie Yuanbin wrote: >> In fact, I have already submitted another patch, which is exactly the way >> as you described: >> Link: https://lore.kernel.org/20251127140109.191657-1-xieyuanbin1@huawei.com >> >> The only difference is that I will move the judgment to before >> local_irq_enable(). The reason for doing this is to fix another bug, >> you can find more details about it here: >> Link: https://lore.kernel.org/20250925025744.6807-1-xieyuanbin1@huawei.com >> Link: https://lore.kernel.org/20251129021815.9679-1-xieyuanbin1@huawei.com > >AFAICS, your patch does nothing to the case when we hit kernel address from >kernel mode, which is what triggers that "block in RCU mode for no good reason" >fun... I'm a little confused. Which patch are you referring to? BTW, I'm trying my best to fix both of these two bugs (might_sleep() in RCU Read Critical Section and missing harden_branch_predictor() mitigation): Link: https://lore.kernel.org/20251126090505.3057219-1-wozizhi@huaweicloud.com Link: https://lore.kernel.org/20250925025744.6807-1-xieyuanbin1@huawei.com at the same time, because I feel that the solutions of these two bugs are very similar in some way. And there is a preliminary solution in place: ```patch diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c index 2bc828a1940c..5c58072d8235 100644 --- a/arch/arm/mm/fault.c +++ b/arch/arm/mm/fault.c @@ -270,10 +270,15 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs) if (kprobe_page_fault(regs, fsr)) return 0; + if (unlikely(addr >= TASK_SIZE)) { + fault = 0; + code = SEGV_MAPERR; + goto bad_area; + } /* Enable interrupts if they were enabled in the parent context. */ if (interrupts_enabled(regs)) local_irq_enable(); ``` Link: https://lore.kernel.org/20251127140109.191657-1-xieyuanbin1@huawei.com I'm not sure if I'm doing the right thing. Do you have any suggestions for this? Thanks very much! Xie Yuanbin