The patch titled Subject: kasan: remove kasan_find_vm_area() to prevent possible deadlock has been added to the -mm mm-hotfixes-unstable branch. Its filename is kasan-remove-kasan_find_vm_area-to-prevent-possible-deadlock.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Yeoreum Yun yeoreum.yun@arm.com Subject: kasan: remove kasan_find_vm_area() to prevent possible deadlock Date: Thu, 3 Jul 2025 19:10:18 +0100

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); <interrupt occurs> <in softirq> spin_lock(&some_lock); <access invalid address> 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().

Link: https://lkml.kernel.org/r/20250703181018.580833-1-yeoreum.yun@arm.com Fixes: c056a364e954 ("kasan: print virtual mapping info in reports") Signed-off-by: Yeoreum Yun yeoreum.yun@arm.com Reported-by: Yunseong Kim ysk@kzalloc.com Cc: Alexander Potapenko glider@google.com Cc: Andrey Konovalov andreyknvl@gmail.com Cc: Andrey Ryabinin ryabinin.a.a@gmail.com Cc: Byungchul Park byungchul@sk.com Cc: Dmitriy Vyukov dvyukov@google.com Cc: Sebastian Andrzej Siewior bigeasy@linutronix.de Cc: Steven Rostedt rostedt@goodmis.org Cc: Vincenzo Frascino vincenzo.frascino@arm.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/kasan/report.c | 45 +------------------------------------------- 1 file changed, 2 insertions(+), 43 deletions(-)

--- a/mm/kasan/report.c~kasan-remove-kasan_find_vm_area-to-prevent-possible-deadlock +++ a/mm/kasan/report.c @@ -370,36 +370,6 @@ static inline bool init_task_stack_addr( sizeof(init_thread_union.stack)); }

-/* - * This function is invoked with report_lock (a raw_spinlock) held. A - * PREEMPT_RT kernel cannot call find_vm_area() as it will acquire a sleeping - * rt_spinlock. - * - * For !RT kernel, the PROVE_RAW_LOCK_NESTING config option will print a - * lockdep warning for this raw_spinlock -> spinlock dependency. This config - * option is enabled by default to ensure better test coverage to expose this - * kind of RT kernel problem. This lockdep splat, however, can be suppressed - * by using DEFINE_WAIT_OVERRIDE_MAP() if it serves a useful purpose and the - * invalid PREEMPT_RT case has been taken care of. - */ -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)) - return NULL; - - /* - * Suppress lockdep warning and fetch vmalloc area of the - * offending address. - */ - lock_map_acquire_try(&vmalloc_map); - va = find_vm_area(addr); - lock_map_release(&vmalloc_map); - return va; -} - static void print_address_description(void *addr, u8 tag, struct kasan_report_info *info) { @@ -429,19 +399,8 @@ static void print_address_description(vo }

if (is_vmalloc_addr(addr)) { - struct vm_struct *va = kasan_find_vm_area(addr); - - if (va) { - pr_err("The buggy address belongs to the virtual mapping at\n" - " [%px, %px) created by:\n" - " %pS\n", - va->addr, va->addr + va->size, va->caller); - pr_err("\n"); - - page = vmalloc_to_page(addr); - } else { - pr_err("The buggy address %px belongs to a vmalloc virtual mapping\n", addr); - } + pr_err("The buggy address %px belongs to a vmalloc virtual mapping\n", addr); + page = vmalloc_to_page(addr); }

if (page) { _

Patches currently in -mm which might be from yeoreum.yun@arm.com are

kasan-remove-kasan_find_vm_area-to-prevent-possible-deadlock.patch