Re: linux-next boot error: BUG: unable to handle kernel NULL pointer dereference in mempool_init_node

[Lorenzo Stoakes]

On Wed, 11 Nov 2020 at 17:44, Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote:
> I'll try to reproduce this and figure out the issue. Thanks for letting us know!

I hope you don't mind me diving in here, I was taking a look just now
and managed to reproduce this locally - I bisected the issue to
105397399 ("kasan: simplify kasan_poison_kfree").

If I stick a simple check in as below it fixes the issue, so I'm
guessing something is violating the assumptions in 105397399?


diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 7a94cebc0324..16163159a017 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -387,6 +387,11 @@ void __kasan_slab_free_mempool(void *ptr, unsigned long ip)
        struct page *page;

        page = virt_to_head_page(ptr);
+
+       if (!PageSlab(page)) {
+               return;
+       }
+
        ____kasan_slab_free(page->slab_cache, ptr, ip, false);
 }


--
Lorenzo Stoakes
https://ljs.io