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[95.203.27.91]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5593c9d0f1fsm2561084e87.107.2025.07.16.02.09.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 16 Jul 2025 02:09:23 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Wed, 16 Jul 2025 11:09:21 +0200 To: Byungchul Park , Yeo Reum Yun , Andrey Konovalov Cc: Yeo Reum Yun , Andrey Konovalov , "akpm@linux-foundation.org" , "glider@google.com" , "dvyukov@google.com" , Vincenzo Frascino , "bigeasy@linutronix.de" , "clrkwllms@kernel.org" , "rostedt@goodmis.org" , "max.byungchul.park@gmail.com" , "ysk@kzalloc.com" , "kasan-dev@googlegroups.com" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "linux-rt-devel@lists.linux.dev" , "kernel_team@skhynix.com" , "urezki@gmail.com" Subject: Re: [PATCH v2] kasan: remove kasan_find_vm_area() to prevent possible deadlock Message-ID: References: <20250703181018.580833-1-yeoreum.yun@arm.com> <20250711020858.GA78977@system.software.com> <20250711021100.GA4320@system.software.com> <20250713232740.GA18327@system.software.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250713232740.GA18327@system.software.com> X-Stat-Signature: a7ejowj1ttqf5g56onti7rmu18y685ha X-Rspamd-Queue-Id: DE5781C000E X-Rspamd-Server: rspam10 X-Rspam-User: X-HE-Tag: 1752656966-897748 X-HE-Meta: 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 PBloAQkW 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 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 Mon, Jul 14, 2025 at 08:27:40AM +0900, Byungchul Park wrote: > On Sat, Jul 12, 2025 at 03:46:10PM +0000, Yeo Reum Yun wrote: > > Hi ByungChul, > > > > [...] > > > I checked the critical section by &vn->busy.lock in find_vm_area(). The > > > time complextity looks O(log N). I don't think an irq disabled section > > > of O(log N) is harmful. I still think using > > > spin_lock_irqsave(&vn->busy.lock) can resolve this issue with no worry > > > of significant irq delay. Am I missing something? > > > > I don't agree for this. > > since in PREEMPT_RT case, it has the same problem. > > > > In case of PREEMPT_RT, spin_lock_irqsave() becomes rt_spin_lock() which is sleepable. > > But, KASAN calls "rt_spin_lock()" holding raw_spin_lock_irqsave() which is definitely wrong. > > It's another issue than irq handling latency, but it's about lock usage > correctness. You are right. > There is vmalloc_dump_obj() function which should be used IMO: pr_err("The buggy address %px belongs to a vmalloc virtual mapping, dump it...\n", addr); vmalloc_dump_obj(addr); we use trylock there to eliminate an issue if invoked from the IRQ context. -- Uladzislau Rezki