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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1qiDQ6-00B20W-Ow; Mon, 18 Sep 2023 12:32:06 +0000 Date: Mon, 18 Sep 2023 13:32:06 +0100 From: Matthew Wilcox To: David Hildenbrand Cc: syzbot , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com Subject: Re: [syzbot] [mm?] WARNING in page_add_anon_rmap Message-ID: References: <0000000000008bf71d06059a2276@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: D0093180009 X-Stat-Signature: 1zrmra86ofrskeaje1pu66p4jhbwuymb X-HE-Tag: 1695040333-30977 X-HE-Meta: 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 Jksgsupb uH/MJJvtwqyjgs+DGFWXiGOxdVuCOGceyxtWavfBByy1izHWnyJFgYY0zvor+gvH5+IR5NC5dvagj2iclQLO3CTbC4UYWeQPmcn61zmyvvctXeC0Q/+4e2EK4+NdQt8Jq1OZB6wXWh9nv+VlabDRY/fszHsR/ZN7LgNQgGBAxLAjzd3exCA1BzKV+0p5TaFU1OwZ8UMrfUjclRMKX6i/3AECHHIp4Q8H7P+zA7axnI/CtWJxclAEMlRDeFQZ4woqLcIFRBlPBAzjhzztvNM7mAI7pyf5SvrDBPXimzdbACNHnOum6RYF9SLE3SY6TDGcjIWg6 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Sep 18, 2023 at 12:00:24PM +0200, David Hildenbrand wrote: > > If you want syzbot to run the reproducer, reply with: > > #syz test: git://repo/address.git branch-or-commit-hash > > If you attach or paste a git patch, syzbot will apply it before testing. If I understand correctly, you have to do it like this: #syz test diff --git a/mm/rmap.c b/mm/rmap.c index 789a2beb8b3a..f13a2927163d 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1249,8 +1249,10 @@ void page_add_anon_rmap(struct page *page, struct vm_area_struct *vma, } if (flags & RMAP_EXCLUSIVE) SetPageAnonExclusive(page); - VM_WARN_ON_FOLIO(page_mapcount(page) > 1 && PageAnonExclusive(page), - folio); + /* While PTE-mapping a THP we have a PMD and a PTE mapping. */ + VM_WARN_ON_FOLIO((atomic_read(&page->_mapcount) > 0 || + (folio_test_large(folio) && folio_entire_mapcount(folio) > 1)) && + PageAnonExclusive(page), folio); mlock_vma_folio(folio, vma, compound); } --