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Thu, 03 Jul 2025 10:12:07 -0700 (PDT) Message-ID: <1a7f32a8-16ff-406c-9542-8d2ad628d7f4@gmail.com> Date: Thu, 3 Jul 2025 19:10:50 +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 Cc: 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, kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, Yunseong Kim References: <20250701203545.216719-1-yeoreum.yun@arm.com> <4599f645-f79c-4cce-b686-494428bb9e2a@gmail.com> Content-Language: en-US From: Andrey Ryabinin In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/2/25 6:04 PM, Yeoreum Yun wrote: > Hi Andrey, > >> >> FYI some of email addresses in CC look corrupted, e.g. "kpm@linux-foundation.org", "nd@arm.com" > > Sorry and Thanks to let me know :) > >> >>> 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. > > Right. unless there is API -- find_vm_area() with spin_trylock(), > kasan_find_vm_area() should be removed. > > But, I'm not sure adding the new API used only bv kasan is better then > just remove kasan_find_vm_area(). > > Do you have any idea for this? > I'd say the info from vm_struct is nice to have, but it's not essential for debugging. It's probably not worth trying to keep it, so I'd vote for for removing kasan_find_vm_area(). > Thanks. > > -- > Sincerely, > Yeoreum Yun