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Received: from viro by zeniv.linux.org.uk with local (Exim 4.99 #2 (Red Hat Linux)) id 1vOKg5-000000007j8-2ErT; Wed, 26 Nov 2025 18:55:45 +0000 Date: Wed, 26 Nov 2025 18:55:45 +0000 From: Al Viro To: Zizhi Wo Cc: jack@suse.com, brauner@kernel.org, hch@lst.de, akpm@linux-foundation.org, linux@armlinux.org.uk, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, wozizhi@huawei.com, yangerkun@huawei.com, wangkefeng.wang@huawei.com, pangliyuan1@huawei.com, xieyuanbin1@huawei.com Subject: Re: [Bug report] hash_name() may cross page boundary and trigger sleep in RCU context Message-ID: <20251126185545.GC3538@ZenIV> References: <20251126090505.3057219-1-wozizhi@huaweicloud.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251126090505.3057219-1-wozizhi@huaweicloud.com> X-Rspamd-Queue-Id: 0B1B1A0003 X-Rspamd-Server: rspam06 X-Rspam-User: X-Stat-Signature: uijninxca35tpm4hoga59o4py8zmo79p X-HE-Tag: 1764183344-508812 X-HE-Meta: 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 CiIfmM30 fsdsYE4GUXKo7nU9Yln2zuMNvI2DuEWAT+gwKeYR3d4x61XfMz0xg1l4lP2Crh7r+hKhfEP5bGidZhR3ZAv110v9xo2jYdtazfE9+MvyDqhqtct2K4bd0ZIvgtMfnO6VRJNKPCVhME316/lIO8TG6Iu95H1avfDw6ek/BV2P5+U5ks8MjhFOOAcaeb7PbNN/qHUJx 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, Nov 26, 2025 at 05:05:05PM +0800, Zizhi Wo wrote: > under an RCU read-side critical section. In linux-mainline, arm/arm64 > do_page_fault() still has this problem: > > lock_mm_and_find_vma->get_mmap_lock_carefully->mmap_read_lock_killable. arm64 shouldn't hit do_page_fault() in the first place, and do_translation_fault() there will see that address is beyond TASK_SIZE and go straight to do_bad_area() -> __do_kernel_fault() -> fixup_exception(), with no messing with mmap_lock. Can anybody confirm that problem exists on arm64 (ideally - with reproducer)?