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X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 03 Jul 2025 19:13:48.1871 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: f0f66b24-01c6-444e-4797-08ddba65bd0f X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d;Ip=[4.158.2.129];Helo=[outbound-uk1.az.dlp.m.darktrace.com] X-MS-Exchange-CrossTenant-AuthSource: DU6PEPF0000A7E4.eurprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: AS8PR08MB9905 X-Stat-Signature: c9qr7mks9m8oq8qwhu5n9zurwepj8ktu X-Rspamd-Queue-Id: 4A33D180004 X-Rspamd-Server: rspam11 X-Rspam-User: X-HE-Tag: 1751570032-129497 X-HE-Meta: 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 ecer0P8l ggrG9aOtDbY3kGbc2JLdj6A2wJKaJNQfr9PAW81va0Pnt9bvB/+8qOaM9GyqWxr3KxxUUStL43tI4pyg= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Andrey, > > > > find_vm_area() couldn't be called in atomic_context. > > > > If find_vm_area() is called to reports vm area information, > > > > kasan can trigger deadlock like: > > > > > > > > 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! > > > > > > > > To prevent possible deadlock while kasan reports, remove kasan_find_vm_area(). > > > > > > Can we keep it for when we are in_task()? > > > > We couldn't do. since when kasan_find_vm_area() is called, > > the report_lock is grabbed with irq disabled. > > > > Please check discuss with Andrey Ryabinin: > > https://lore.kernel.org/all/4599f645-f79c-4cce-b686-494428bb9e2a@gmail.com/ > > That was about checking for !in_interrupt(), but I believe checking > for in_task() is different? But I'm not an expert on these checks. I think below secnario can explain why we couldn't use in_task(). CPU0 CPU1 vmalloc(); alloc_vmap_area(); spin_lock(&vn->busy.lock) spin_lock_irqsaved(&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! If you call in_task() in CPU1 before calling find_vm_area(), it returns true and try to call find_vm_area() so it still makes a deadlock situation. Thanks -- Sincerely, Yeoreum Yun