linux-kernel - Re: [mm] 2037ab69a5: BUG:KASAN:null-ptr-deref_in

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Message-ID: <20200914112738.GM6583@casper.infradead.org>
Date:   Mon, 14 Sep 2020 12:27:38 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     kernel test robot <lkp@...el.com>
Cc:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        Hugh Dickins <hughd@...gle.com>,
        William Kucharski <william.kucharski@...cle.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Matthew Auld <matthew.auld@...el.com>,
        Huang Ying <ying.huang@...el.com>,
        intel-gfx@...ts.freedesktop.org, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org, lkp@...ts.01.org
Subject: Re: [mm] 2037ab69a5: BUG:KASAN:null-ptr-deref_in_t

On Mon, Sep 14, 2020 at 04:55:45PM +0800, kernel test robot wrote:
> Greeting,
> 
> FYI, we noticed the following commit (built with gcc-9):
> 
> commit: 2037ab69a5cd8afe58347135010f6160ea368dd0 ("mm: Convert find_get_entry to return the head page")

Thank you!

diff --git a/mm/swap_state.c b/mm/swap_state.c
index c2fb62f660a5..a22c2430e80c 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -427,6 +427,8 @@ struct page *find_get_incore_page(struct address_space *mapping, pgoff_t index)
 	struct swap_info_struct *si;
 	struct page *page = find_get_entry(mapping, index);
 
+	if (!page)
+		return page;
 	if (!xa_is_value(page))
 		return find_subpage(page, index);
 	if (!shmem_mapping(mapping))