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[83.28.84.110]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b7077c8e323sm1015515366b.54.2025.11.03.02.39.12 (version=TLS1_2 cipher=AES128-SHA bits=128/128); Mon, 03 Nov 2025 02:39:13 -0800 (PST) Date: Mon, 3 Nov 2025 11:39:07 +0100 From: Michal Pecio To: Sebastian Andrzej Siewior Cc: bp@alien8.de, da.gomez@samsung.com, dave.hansen@linux.intel.com, hpa@zytor.com, jpoimboe@kernel.org, linux-kernel@vger.kernel.org, linux-modules@vger.kernel.org, mcgrof@kernel.org, mingo@redhat.com, paulmck@kernel.org, peterz@infradead.org, petr.pavlu@suse.com, samitolvanen@google.com, tglx@linutronix.de, x86@kernel.org Subject: Re: [PATCH v3 22/28] x86: Use RCU in all users of __module_address(). Message-ID: <20251103113907.4e647f33.michal.pecio@gmail.com> In-Reply-To: <20251103103434.D6m23Iud@linutronix.de> References: <20250108090457.512198-23-bigeasy@linutronix.de> <20251103110835.1dca378c.michal.pecio@gmail.com> <20251103103434.D6m23Iud@linutronix.de> Precedence: bulk X-Mailing-List: linux-modules@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Mon, 3 Nov 2025 11:34:34 +0100, Sebastian Andrzej Siewior wrote: > On 2025-11-03 11:08:35 [+0100], Michal Pecio wrote: > > Hi, > Hi, > > > There is a regression report on a distribution forum which involves > > an out of tree module on a patched kernel (yes, I know) calling > > stack_trace_save() in task context, which arrives here and apparently > > calls the various deref_stack_xxx() functions with preemption enabled, > > which in turn call stack_access_ok() leading to a BUG: > > > > Nov 02 21:44:30 ArchBasement kernel: BUG: using smp_processor_id() in preemptible [00000000] code: Xorg/1183 > > Nov 02 21:44:30 ArchBasement kernel: caller is in_entry_stack+0x11/0x60 > > Nov 02 21:44:30 ArchBasement kernel: CPU: 0 UID: 1000 PID: 1183 Comm: Xorg Tainted: P OE 6.16.12-hardened1-1-hardened #1 PREEMPT(full) 6edb90a7a07fab33bbee72d6d5ef53ba6eec3b9c > > Nov 02 21:44:30 ArchBasement kernel: Tainted: [P]=PROPRIETARY_MODULE, [O]=OOT_MODULE, [E]=UNSIGNED_MODULE > > Nov 02 21:44:30 ArchBasement kernel: Hardware name: ASUS All Series/Z97-E, BIOS 0803 02/23/2016 > > Nov 02 21:44:30 ArchBasement kernel: Call Trace: > > Nov 02 21:44:30 ArchBasement kernel: > > Nov 02 21:44:30 ArchBasement kernel: dump_stack_lvl+0x5d/0x80 > > Nov 02 21:44:30 ArchBasement kernel: check_preemption_disabled+0xe5/0xf0 > > Nov 02 21:44:30 ArchBasement kernel: in_entry_stack+0x11/0x60 > > Nov 02 21:44:30 ArchBasement kernel: get_stack_info+0x2c/0x80 > > Nov 02 21:44:30 ArchBasement kernel: stack_access_ok+0x51/0xa0 > > Nov 02 21:44:30 ArchBasement kernel: unwind_next_frame+0x1cb/0x7b0 > > Nov 02 21:44:30 ArchBasement kernel: ? _nv003168kms+0x42/0x50 [nvidia_modeset 90775ea8a26c5e58b97ef4b3f46eb45efa040eb2] > > Nov 02 21:44:30 ArchBasement kernel: ? __pfx_stack_trace_consume_entry+0x10/0x10 > > Nov 02 21:44:30 ArchBasement kernel: arch_stack_walk+0xa6/0x110 > > Nov 02 21:44:30 ArchBasement kernel: ? _nv003168kms+0x42/0x50 [nvidia_modeset 90775ea8a26c5e58b97ef4b3f46eb45efa040eb2] > > Nov 02 21:44:30 ArchBasement kernel: stack_trace_save+0x4d/0x70 > > > > Is this nvidia doing something wrong, or a problem with this commit? > > > > The removed code suggests that preemption is allowed here, and as far > > as I see, this call trace is still possible on vanilla 6.18. Perhaps > > preempt_disable() needs to be restored around this code? > > Do you have the complete backtrace? Is this SMP or UP build? Sorry, I forgot to include the link. There is also a similar warning regarding __this_cpu_read(). Pretty sure the kernel is SMP. https://bbs.archlinux.org/viewtopic.php?id=309960