From: Aleksei Nikiforov Date: Tue, 30 Sep 2025 11:56:01 +0000 (+0200) Subject: mm/kmsan: fix kmsan kmalloc hook when no stack depots are allocated yet X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=faad46b1d1808e334d2cd098ff620dbb397e11d9;p=users%2Fjedix%2Flinux-maple.git mm/kmsan: fix kmsan kmalloc hook when no stack depots are allocated yet If no stack depot is allocated yet, due to masking out __GFP_RECLAIM flags kmsan called from kmalloc cannot allocate stack depot. kmsan fails to record origin and report issues. This may result in KMSAN failing to report issues. Reusing flags from kmalloc without modifying them should be safe for kmsan. For example, such chain of calls is possible: test_uninit_kmalloc -> kmalloc -> __kmalloc_cache_noprof -> slab_alloc_node -> slab_post_alloc_hook -> kmsan_slab_alloc -> kmsan_internal_poison_memory. Only when it is called in a context without flags present should __GFP_RECLAIM flags be masked. With this change all kmsan tests start working reliably. Link: https://lkml.kernel.org/r/20250930115600.709776-2-aleksei.nikiforov@linux.ibm.com Signed-off-by: Aleksei Nikiforov Cc: Alexander Potapenko Cc: Dmitriy Vyukov Cc: Ilya Leoshkevich Cc: Marco Elver Signed-off-by: Andrew Morton --- diff --git a/mm/kmsan/core.c b/mm/kmsan/core.c index bd612e5aa7b4..90f427b95a21 100644 --- a/mm/kmsan/core.c +++ b/mm/kmsan/core.c @@ -72,9 +72,6 @@ depot_stack_handle_t kmsan_save_stack_with_flags(gfp_t flags, nr_entries = stack_trace_save(entries, KMSAN_STACK_DEPTH, 0); - /* Don't sleep. */ - flags &= ~(__GFP_DIRECT_RECLAIM | __GFP_KSWAPD_RECLAIM); - handle = stack_depot_save(entries, nr_entries, flags); return stack_depot_set_extra_bits(handle, extra); } diff --git a/mm/kmsan/hooks.c b/mm/kmsan/hooks.c index 2cee59d89c80..8f22d1f22981 100644 --- a/mm/kmsan/hooks.c +++ b/mm/kmsan/hooks.c @@ -84,7 +84,8 @@ void kmsan_slab_free(struct kmem_cache *s, void *object) if (s->ctor) return; kmsan_enter_runtime(); - kmsan_internal_poison_memory(object, s->object_size, GFP_KERNEL, + kmsan_internal_poison_memory(object, s->object_size, + GFP_KERNEL & ~(__GFP_RECLAIM), KMSAN_POISON_CHECK | KMSAN_POISON_FREE); kmsan_leave_runtime(); } @@ -114,7 +115,8 @@ void kmsan_kfree_large(const void *ptr) kmsan_enter_runtime(); page = virt_to_head_page((void *)ptr); KMSAN_WARN_ON(ptr != page_address(page)); - kmsan_internal_poison_memory((void *)ptr, page_size(page), GFP_KERNEL, + kmsan_internal_poison_memory((void *)ptr, page_size(page), + GFP_KERNEL & ~(__GFP_RECLAIM), KMSAN_POISON_CHECK | KMSAN_POISON_FREE); kmsan_leave_runtime(); } diff --git a/mm/kmsan/shadow.c b/mm/kmsan/shadow.c index 3cd733663100..e7f554a31bb4 100644 --- a/mm/kmsan/shadow.c +++ b/mm/kmsan/shadow.c @@ -208,7 +208,7 @@ void kmsan_free_page(struct page *page, unsigned int order) return; kmsan_enter_runtime(); kmsan_internal_poison_memory(page_address(page), page_size(page), - GFP_KERNEL, + GFP_KERNEL & ~(__GFP_RECLAIM), KMSAN_POISON_CHECK | KMSAN_POISON_FREE); kmsan_leave_runtime(); }