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([2601:188:c100:5710:627d:9ff:fe85:9ade]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6e659e49ae1sm2715296d6.124.2025.02.12.05.34.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 12 Feb 2025 05:34:08 -0800 (PST) From: Waiman Long X-Google-Original-From: Waiman Long Message-ID: Date: Wed, 12 Feb 2025 08:34:06 -0500 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 RT kernel To: Andrey Ryabinin Cc: Alexander Potapenko , Andrey Konovalov , Dmitry Vyukov , Vincenzo Frascino , Andrew Morton , Sebastian Andrzej Siewior , Clark Williams , Steven Rostedt , kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, Nico Pache References: <20250211160750.1301353-1-longman@redhat.com> Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 2/12/25 6:59 AM, Andrey Ryabinin wrote: > On Tue, Feb 11, 2025 at 5:08 PM Waiman Long wrote: >> diff --git a/mm/kasan/report.c b/mm/kasan/report.c >> index 3fe77a360f1c..e1ee687966aa 100644 >> --- a/mm/kasan/report.c >> +++ b/mm/kasan/report.c >> @@ -398,9 +398,20 @@ static void print_address_description(void *addr, u8 tag, >> pr_err("\n"); >> } >> >> - if (is_vmalloc_addr(addr)) { >> - struct vm_struct *va = find_vm_area(addr); >> + if (!is_vmalloc_addr(addr)) >> + goto print_page; >> >> + /* >> + * RT kernel cannot call find_vm_area() in atomic context. >> + * For !RT kernel, prevent spinlock_t inside raw_spinlock_t warning >> + * by raising wait-type to WAIT_SLEEP. >> + */ >> + if (!IS_ENABLED(CONFIG_PREEMPT_RT)) { >> + static DEFINE_WAIT_OVERRIDE_MAP(vmalloc_map, LD_WAIT_SLEEP); >> + struct vm_struct *va; >> + >> + lock_map_acquire_try(&vmalloc_map); >> + va = find_vm_area(addr); > Can we hide all this logic behind some function like > kasan_find_vm_area() which would return NULL for -rt? Sure. We can certainly do that. > >> if (va) { >> pr_err("The buggy address belongs to the virtual mapping at\n" >> " [%px, %px) created by:\n" >> @@ -410,8 +421,13 @@ static void print_address_description(void *addr, u8 tag, >> >> page = vmalloc_to_page(addr); > Or does vmalloc_to_page() secretly take some lock somewhere so we > need to guard it with this 'vmalloc_map' too? > So my suggestion above wouldn't be enough, if that's the case. AFAICS, vmalloc_to_page() doesn't seem to take any lock.  Even if it takes another spinlock, it will still be under the vmalloc_map protection until lock_map_release() is called. Cheers, Longman