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Thu, 27 Nov 2025 11:01:42 +0800 (CST) Received: from kwepemj100009.china.huawei.com (unknown [7.202.194.3]) by mail.maildlp.com (Postfix) with ESMTPS id 719521402C4; Thu, 27 Nov 2025 11:03:31 +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; Thu, 27 Nov 2025 11:03:30 +0800 From: Xie Yuanbin To: , , , , CC: , , , , , , , , , , , , , , , , , , , , , , , , , , , Xie Yuanbin Subject: [RFC PATCH] vfs: Fix might sleep in load_unaligned_zeropad() with rcu read lock held Date: Thu, 27 Nov 2025 11:03:16 +0800 Message-ID: <20251127030316.8396-1-xieyuanbin1@huawei.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Originating-IP: [10.67.109.17] X-ClientProxiedBy: kwepems100002.china.huawei.com (7.221.188.206) To kwepemj100009.china.huawei.com (7.202.194.3) X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 26D54100002 X-Stat-Signature: 6rhg9g9fawub4qxhjprk3foiwy7nnom8 X-Rspam-User: X-HE-Tag: 1764212616-689830 X-HE-Meta: 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 7la/hSE+ TylJIqrUDYjsqCJTCln2VHvcoSro+BtOYFrVY1vy1bfCs3QbE37nfBXZSPqzwOUu1Qc/8Qq6QCx1dcjky6cWZiMB1fJns5MQ0Rq2gASwLZwMjiFL97o5mELvrOwSn30nEvxeK8HymQzLKfoHl+H9cekeVsC3zTMTm1qY2WlBC+r6jdfdScNM9t7ZTrWAKq0Ay6FZECqUEk9Mwtm6gTcOMdNYI2wYL1A5Vq+donWHnAFzsUceZlz+iwqFnCRnpgtuGPRGIAeeMf21Yx5ivW29rKbNrcNHv5GvsBhBFfIKmI0u3AXG7L+kq5PjE+3MEhJGh1b8w69bvbVa2vioKgjkVLH5ETU1FT/gA91S1f+cdtvQZgqgOclMBrLcZcFyvHxQ4vwToGwHJF7upiIW5Yzgl6QXQlhDf3FnZsvG8iT/OCTMUOBHjwu7m9OoXag== 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, Wed, 26 Nov 2025 19:26:40 +0000, Al Viro wrote: > For quick and dirty variant (on current tree), how about > adding > if (unlikely(addr > TASK_SIZE) && !user_mode(regs)) > goto no_context; > > right after > > if (!ttbr0_usermode_access_allowed(regs)) > goto no_context; > > in do_page_fault() there? On, Wed, 26 Nov 2025 23:31:00 +0000, Russell King (Oracle) wrote: > Now, for 32-bit ARM, I think I am coming to the conclusion that Al's > suggestion is probably the easiest solution. However, whether it has > side effects, I couldn't say - the 32-bit ARM fault code has been > modified by quite a few people in ways I don't yet understand, so I > can't be certain at the moment whether it would cause problems. I think I've already submitted a very similar patch, to fix another bug: On Thu, 16 Oct 2025 20:16:21 +0800, Xie Yuanbin wrote: > +#ifdef CONFIG_HARDEN_BRANCH_PREDICTOR > + if (unlikely(addr > TASK_SIZE) && user_mode(regs)) { > + fault = 0; > + code = SEGV_MAPERR; > + goto bad_area; > + } > +#endif Link: https://lore.kernel.org/20250925025744.6807-1-xieyuanbin1@huawei.com However, the patch seems to have received no response for a very long time. On Wed, 26 Nov 2025 23:31:00 +0000, Russell King wrote: > I think the only thing to do is to try the solution and see what > breaks. I'm not in a position to be able to do that as, having not > had reason to touch 32-bit ARM for years, I don't have a hackable > platform nearby. Maybe Xie Yuanbin can test it? With pleasure. By the way, for the config and test case shown in this patch: vfs: Fix might sleep in load_unaligned_zeropad() with rcu read lock held Link: https://lore.kernel.org/20251126101952.174467-1-xieyuanbin1@huawei.com the warning can be reproduced directly on QEMU. Xie Yuanbin