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Wed, 02 Jul 2025 08:47:40 -0700 (PDT) Message-ID: <4599f645-f79c-4cce-b686-494428bb9e2a@gmail.com> Date: Wed, 2 Jul 2025 17:46:23 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] kasan: don't call find_vm_area() in in_interrupt() for possible deadlock To: Yeoreum Yun , glider@google.com, andreyknvl@gmail.com, dvyukov@google.com, vincenzo.frascino@arm.com, akpm@linux-foundation.org, bigeasy@linutronix.de, clrkwllms@kernel.org, rostedt@goodmis.org, byungchul@sk.com, max.byungchul.park@gmail.com Cc: kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, nd@arm.com, Yunseong Kim References: <20250701203545.216719-1-yeoreum.yun@arm.com> Content-Language: en-US From: Andrey Ryabinin In-Reply-To: <20250701203545.216719-1-yeoreum.yun@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/1/25 10:35 PM, Yeoreum Yun wrote: FYI some of email addresses in CC look corrupted, e.g. "kpm@linux-foundation.org", "nd@arm.com" > In below senario, kasan causes deadlock while reporting vm area informaion: > > CPU0 CPU1 > vmalloc(); > 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! > ... > diff --git a/mm/kasan/report.c b/mm/kasan/report.c > index 8357e1a33699..61c590e8005e 100644 > --- a/mm/kasan/report.c > +++ b/mm/kasan/report.c > @@ -387,7 +387,7 @@ static inline struct vm_struct *kasan_find_vm_area(void *addr) > static DEFINE_WAIT_OVERRIDE_MAP(vmalloc_map, LD_WAIT_SLEEP); > struct vm_struct *va; > > - if (IS_ENABLED(CONFIG_PREEMPT_RT)) > + if (IS_ENABLED(CONFIG_PREEMPT_RT) || in_interrupt()) in_interrupt() returns true if BH disabled, so this indeed should avoid the deadlock. However, it seems we have similar problem with 'spin_lock_irq[save](&some_lock)' case and in_interrupt() check doesn't fix it. And adding irqs_disabled() check wouldn't make sense because print_report() always runs with irqs disabled. I see no obvious way to fix this rather than remove find_vm_area() call completely and just print less info.