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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 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> In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: W046sUoBN5LxX45v_1awIjLnU70zNFKnZrf6DAafu8U_1739367250 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: 794D2120012 X-Rspamd-Server: rspam12 X-Stat-Signature: h41r97rpjfzyrzwwgqts1nfcmm8ti36s X-HE-Tag: 1739367252-296839 X-HE-Meta: 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 Yd8e0WZB 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000004, 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 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