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s=arc-20220608; d=hostedemail.com; t=1752199746; a=rsa-sha256; cv=none; b=V2wMpG5/G/oLr5OCxw4x0+eQL/fBonEY8UCL3iJraToEqHlsjF2gSEfy3/gZ/qPG0jphVB RrnwBQ0J44NKT5rMWIuRxgBuuN1U5KUrSn07mpBuYP21GqYoNasytLD+nLbOxgcZf57w3e s0sDgGXHtX80T8elG/qC7GXg+ubsF5w= ARC-Authentication-Results: i=1; imf11.hostedemail.com; dkim=none; dmarc=none; spf=pass (imf11.hostedemail.com: domain of byungchul@sk.com designates 166.125.252.92 as permitted sender) smtp.mailfrom=byungchul@sk.com X-AuditID: a67dfc5b-669ff7000002311f-28-6870723f8102 Date: Fri, 11 Jul 2025 11:08:58 +0900 From: Byungchul Park To: Andrey Konovalov Cc: Yeoreum Yun , akpm@linux-foundation.org, glider@google.com, dvyukov@google.com, vincenzo.frascino@arm.com, 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 Subject: Re: [PATCH v2] kasan: remove kasan_find_vm_area() to prevent possible deadlock Message-ID: <20250711020858.GA78977@system.software.com> References: <20250703181018.580833-1-yeoreum.yun@arm.com> MIME-Version: 1.0 Content-Type: text/plain; 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> > alloc_vmap_area(); > > spin_lock(&vn->busy.lock) > > spin_lock_bh(&some_lock); > > > > > > spin_lock(&some_lock); > > > > kasan_report(); > > print_report(); > > print_address_description(); > > kasan_find_vm_area(); > > find_vm_area(); > > spin_lock(&vn->busy.lock) // deadlock! > > > > To prevent possible deadlock while kasan reports, remove kasan_find_vm_area(). > > > > Fixes: c056a364e954 ("kasan: print virtual mapping info in reports") > > Reported-by: Yunseong Kim > > Signed-off-by: Yeoreum Yun > > As a fix: > > Acked-by: Andrey Konovalov > > But it would be great to figure out a way to eventually restore this > functionality; I'll file a bug for this once this patch lands. The > virtual mapping info helps with real issues: e.g. just recently it > helped me to quickly see the issue that caused a false-positive report 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? If it's unacceptable for some reasons, why don't we introduce kind of try_find_vm_area() using trylock so as to go ahead only if there's no lock contention? Byungchul > [1]. > > [1] https://lore.kernel.org/all/CA+fCnZfzHOFjVo43UZK8H6h3j=OHjfF13oFJvT0P-SM84Oc4qQ@mail.gmail.com/