From f70b00496f2a0669fdb19a783e613bdbdedcf901 Mon Sep 17 00:00:00 2001 From: Alexander Potapenko Date: Sat, 22 May 2021 17:41:56 -0700 Subject: [PATCH] kasan: slab: always reset the tag in get_freepointer_safe() With CONFIG_DEBUG_PAGEALLOC enabled, the kernel should also untag the object pointer, as done in get_freepointer(). Failing to do so reportedly leads to SLUB freelist corruptions that manifest as boot-time crashes. Link: https://lkml.kernel.org/r/20210514072228.534418-1-glider@google.com Signed-off-by: Alexander Potapenko Cc: Marco Elver Cc: Vincenzo Frascino Cc: Andrey Ryabinin Cc: Andrey Konovalov Cc: Elliot Berman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/slub.c | 1 + 1 file changed, 1 insertion(+) diff --git a/mm/slub.c b/mm/slub.c index 438fa8d..3f96e09 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -301,6 +301,7 @@ static inline void *get_freepointer_safe(struct kmem_cache *s, void *object) if (!debug_pagealloc_enabled_static()) return get_freepointer(s, object); + object = kasan_reset_tag(object); freepointer_addr = (unsigned long)object + s->offset; copy_from_kernel_nofault(&p, (void **)freepointer_addr, sizeof(p)); return freelist_ptr(s, p, freepointer_addr); -- 2.7.4