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Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.98 #2 (Red Hat Linux)) id 1t4EsK-00000004yAz-2FqZ; Fri, 25 Oct 2024 07:36:49 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 4FABA30083E; Fri, 25 Oct 2024 09:36:48 +0200 (CEST) Date: Fri, 25 Oct 2024 09:36:48 +0200 From: Peter Zijlstra To: Shawn Wang Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Liam.Howlett@oracle.com, akpm@linux-foundation.org, baolin.wang@linux.alibaba.com, mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com Subject: Re: [PATCH] sched/numa: Fix the potential null pointer dereference in task_numa_work() Message-ID: <20241025073648.GA14555@noisy.programming.kicks-ass.net> References: <20241025022208.125527-1-shawnwang@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241025022208.125527-1-shawnwang@linux.alibaba.com> X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 123151C0002 X-Stat-Signature: dqryfawo6gnn1ws47qqdoemn5s3y4gth X-HE-Tag: 1729841778-444035 X-HE-Meta: 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 BzJ7ZEkn 8kUUozdndI3tticQIOTEmIuFsM3dN1+pNUXc5H3j5WG2X26K8gmdKn+xOocrTD+4SHeu6qysC1vp8C/Ken+38mwCDJJvOSmaCk6nZ9VUT+NoV2uq2L6pJcP9twrjFtsadIGQc2lpR12cd7xwlkfSON1E+EuFMsShjHi0QAKlx42Vhm73zAHJZf3mFLX07wYfOntDMijXr1Jk9lDVL8d1CHf3seVaMtj/+mGhyCY+RXuFtiSFugvAndlgqi+uVHJ3MXZx3R3SYyKeSd6w= 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 Fri, Oct 25, 2024 at 10:22:08AM +0800, Shawn Wang wrote: > When running stress-ng-vm-segv test, we found a null pointer dereference > error in task_numa_work(). Here is the backtrace: > > [323676.066985] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000020 > ...... > [323676.067108] CPU: 35 PID: 2694524 Comm: stress-ng-vm-se > ...... > [323676.067113] pstate: 23401009 (nzCv daif +PAN -UAO +TCO +DIT +SSBS BTYPE=--) > [323676.067115] pc : vma_migratable+0x1c/0xd0 > [323676.067122] lr : task_numa_work+0x1ec/0x4e0 > [323676.067127] sp : ffff8000ada73d20 > [323676.067128] x29: ffff8000ada73d20 x28: 0000000000000000 x27: 000000003e89f010 > [323676.067130] x26: 0000000000080000 x25: ffff800081b5c0d8 x24: ffff800081b27000 > [323676.067133] x23: 0000000000010000 x22: 0000000104d18cc0 x21: ffff0009f7158000 > [323676.067135] x20: 0000000000000000 x19: 0000000000000000 x18: ffff8000ada73db8 > [323676.067138] x17: 0001400000000000 x16: ffff800080df40b0 x15: 0000000000000035 > [323676.067140] x14: ffff8000ada73cc8 x13: 1fffe0017cc72001 x12: ffff8000ada73cc8 > [323676.067142] x11: ffff80008001160c x10: ffff000be639000c x9 : ffff8000800f4ba4 > [323676.067145] x8 : ffff000810375000 x7 : ffff8000ada73974 x6 : 0000000000000001 > [323676.067147] x5 : 0068000b33e26707 x4 : 0000000000000001 x3 : ffff0009f7158000 > [323676.067149] x2 : 0000000000000041 x1 : 0000000000004400 x0 : 0000000000000000 > [323676.067152] Call trace: > [323676.067153] vma_migratable+0x1c/0xd0 > [323676.067155] task_numa_work+0x1ec/0x4e0 > [323676.067157] task_work_run+0x78/0xd8 > [323676.067161] do_notify_resume+0x1ec/0x290 > [323676.067163] el0_svc+0x150/0x160 > [323676.067167] el0t_64_sync_handler+0xf8/0x128 > [323676.067170] el0t_64_sync+0x17c/0x180 > [323676.067173] Code: d2888001 910003fd f9000bf3 aa0003f3 (f9401000) > [323676.067177] SMP: stopping secondary CPUs > [323676.070184] Starting crashdump kernel... > > stress-ng-vm-segv in stress-ng is used to stress test the SIGSEGV error > handling function of the system, which tries to cause a SIGSEGV error on > return from unmapping the whole address space of the child process. > > Normally this program will not cause kernel crashes. But before the > munmap system call returns to user mode, a potential task_numa_work() > for numa balancing could be added and executed. In this scenario, since the > child process has no vma after munmap, the vma_next() in task_numa_work() > will return a null pointer even if the vma iterator restarts from 0. > > Recheck the vma pointer before dereferencing it in task_numa_work(). > > Fixes: 214dbc428137 ("sched: convert to vma iterator") > Cc: stable@vger.kernel.org # v6.2+ Thanks