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[99.254.121.117]) by smtp.gmail.com with ESMTPSA id j17-20020ac86651000000b0041b3deef647sm33619qtp.8.2023.11.16.12.04.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 16 Nov 2023 12:04:06 -0800 (PST) Date: Thu, 16 Nov 2023 15:04:04 -0500 From: Peter Xu To: David Hildenbrand Cc: Andrew Morton , syzbot , Muhammad Usama Anjum , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com, wangkefeng.wang@huawei.com Subject: Re: [syzbot] [mm?] WARNING in unmap_page_range (2) Message-ID: References: <000000000000b0e576060a30ee3b@google.com> <20231115140006.cc7de06f89b1f885f4583af0@linux-foundation.org> <6308590a-d958-4ecc-a478-ba088cf7984d@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <6308590a-d958-4ecc-a478-ba088cf7984d@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 16, 2023 at 07:13:44PM +0100, David Hildenbrand wrote: > > It should be fine, as: > > > > static void make_uffd_wp_pte(struct vm_area_struct *vma, > > unsigned long addr, pte_t *pte) > > { > > pte_t ptent = ptep_get(pte); > > > > #ifndef CONFIG_USERFAULTFD_ > > > > if (pte_present(ptent)) { > > pte_t old_pte; > > > > old_pte = ptep_modify_prot_start(vma, addr, pte); > > ptent = pte_mkuffd_wp(ptent); > > ptep_modify_prot_commit(vma, addr, pte, old_pte, ptent); > > } else if (is_swap_pte(ptent)) { > > ptent = pte_swp_mkuffd_wp(ptent); > > set_pte_at(vma->vm_mm, addr, pte, ptent); > > } else { <----------------- this must be pte_none() already > > set_pte_at(vma->vm_mm, addr, pte, > > make_pte_marker(PTE_MARKER_UFFD_WP)); > > } > > } > > Indeed! Is pte_swp_mkuffd_wp() reasonable for pte markers? I rememebr that > we don't support multiple markers yet, so it might be good enough. Not really that reasonable, but nothing harmful either that I see so far; the current code handles any pte marker without caring any of those hint bits. I can also reproduce this syzbot error easily with !UFFD config on x86. Let me send the patchset to fix current known issues first. Thanks, -- Peter Xu