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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id p82-20020a815b55000000b00561e7639ee8sm296391ywb.57.2023.06.08.18.26.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Jun 2023 18:26:07 -0700 (PDT) Date: Thu, 8 Jun 2023 18:26:04 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@ripple.attlocal.net To: Andrew Morton cc: Mike Kravetz , Mike Rapoport , "Kirill A. Shutemov" , Matthew Wilcox , David Hildenbrand , Suren Baghdasaryan , Qi Zheng , Yang Shi , Mel Gorman , Peter Xu , Peter Zijlstra , Will Deacon , Yu Zhao , Alistair Popple , Ralph Campbell , Ira Weiny , Steven Price , SeongJae Park , Lorenzo Stoakes , Huang Ying , Naoya Horiguchi , Christophe Leroy , Zack Rusin , Jason Gunthorpe , Axel Rasmussen , Anshuman Khandual , Pasha Tatashin , Miaohe Lin , Minchan Kim , Christoph Hellwig , Song Liu , Thomas Hellstrom , Ryan Roberts , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v2 15/32] mm/userfaultfd: allow pte_offset_map_lock() to fail In-Reply-To: Message-ID: <50cf3930-1bfa-4de9-a079-3da47b7ce17b@google.com> References: MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" mfill_atomic_install_pte() and mfill_atomic_pte_zeropage() treat failed pte_offset_map_lock() as -EAGAIN, which mfill_atomic() already returns to user for a similar race. Signed-off-by: Hugh Dickins --- mm/userfaultfd.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index e97a0b4889fc..5fd787158c70 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -76,7 +76,10 @@ int mfill_atomic_install_pte(pmd_t *dst_pmd, if (flags & MFILL_ATOMIC_WP) _dst_pte =3D pte_mkuffd_wp(_dst_pte); =20 + ret =3D -EAGAIN; dst_pte =3D pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl); + if (!dst_pte) + goto out; =20 if (vma_is_shmem(dst_vma)) { /* serialize against truncate with the page table lock */ @@ -121,6 +124,7 @@ int mfill_atomic_install_pte(pmd_t *dst_pmd, ret =3D 0; out_unlock: pte_unmap_unlock(dst_pte, ptl); +out: return ret; } =20 @@ -212,7 +216,10 @@ static int mfill_atomic_pte_zeropage(pmd_t *dst_pmd, =20 _dst_pte =3D pte_mkspecial(pfn_pte(my_zero_pfn(dst_addr), dst_vma->vm_page_prot)); + ret =3D -EAGAIN; dst_pte =3D pte_offset_map_lock(dst_vma->vm_mm, dst_pmd, dst_addr, &ptl); + if (!dst_pte) + goto out; if (dst_vma->vm_file) { /* the shmem MAP_PRIVATE case requires checking the i_size */ inode =3D dst_vma->vm_file->f_inode; @@ -231,6 +238,7 @@ static int mfill_atomic_pte_zeropage(pmd_t *dst_pmd, ret =3D 0; out_unlock: pte_unmap_unlock(dst_pte, ptl); +out: return ret; } =20 --=20 2.35.3