The patch titled Subject: mm/pagemap: fix ioctl(PAGEMAP_SCAN) on vma check has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-pagemap-fix-ioctlpagemap_scan-on-vma-check.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-pagemap-fix-ioctlpagemap_scan-on-vma-check.patch This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Peter Xu <peterx@xxxxxxxxxx> Subject: mm/pagemap: fix ioctl(PAGEMAP_SCAN) on vma check Date: Thu, 16 Nov 2023 15:15:45 -0500 Patch series "mm/pagemap: A few fixes to the recent PAGEMAP_SCAN". This series should fix two known reports from syzbot on the new PAGEMAP_SCAN ioctl(): https://lore.kernel.org/all/000000000000b0e576060a30ee3b@xxxxxxxxxx/ https://lore.kernel.org/all/000000000000773fa7060a31e2cc@xxxxxxxxxx/ The 3rd patch is something I found when testing these patches. This patch (of 3): The new ioctl(PAGEMAP_SCAN) relies on vma wr-protect capability provided by userfault, however in the vma test it didn't explicitly require the vma to have wr-protect function enabled, even if PM_SCAN_WP_MATCHING flag is set. It means the pagemap code can now apply uffd-wp bit to a page in the vma even if not registered to userfaultfd at all. Then in whatever way as long as the pte got written and page fault resolved, we'll apply the write bit even if uffd-wp bit is set. We'll see a pte that has both UFFD_WP and WRITE bit set. Anything later that looks up the pte for uffd-wp bit will trigger the warning: WARNING: CPU: 1 PID: 5071 at arch/x86/include/asm/pgtable.h:403 pte_uffd_wp arch/x86/include/asm/pgtable.h:403 [inline] Fix it by doing proper check over the vma attributes when PM_SCAN_WP_MATCHING is specified. Link: https://lkml.kernel.org/r/20231116201547.536857-1-peterx@xxxxxxxxxx Link: https://lkml.kernel.org/r/20231116201547.536857-2-peterx@xxxxxxxxxx Fixes: 52526ca7fdb9 ("fs/proc/task_mmu: implement IOCTL to get and optionally clear info about PTEs") Signed-off-by: Peter Xu <peterx@xxxxxxxxxx> Reported-by: syzbot+e94c5aaf7890901ebf9b@xxxxxxxxxxxxxxxxxxxxxxxxx Cc: Andrei Vagin <avagin@xxxxxxxxx> Cc: David Hildenbrand <david@xxxxxxxxxx> Cc: Muhammad Usama Anjum <usama.anjum@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/proc/task_mmu.c | 24 ++++++++++++++++++++---- 1 file changed, 20 insertions(+), 4 deletions(-) --- a/fs/proc/task_mmu.c~mm-pagemap-fix-ioctlpagemap_scan-on-vma-check +++ a/fs/proc/task_mmu.c @@ -1982,15 +1982,31 @@ static int pagemap_scan_test_walk(unsign struct pagemap_scan_private *p = walk->private; struct vm_area_struct *vma = walk->vma; unsigned long vma_category = 0; + bool wp_allowed = userfaultfd_wp_async(vma) && + userfaultfd_wp_use_markers(vma); - if (userfaultfd_wp_async(vma) && userfaultfd_wp_use_markers(vma)) - vma_category |= PAGE_IS_WPALLOWED; - else if (p->arg.flags & PM_SCAN_CHECK_WPASYNC) - return -EPERM; + if (!wp_allowed) { + /* User requested explicit failure over wp-async capability */ + if (p->arg.flags & PM_SCAN_CHECK_WPASYNC) + return -EPERM; + /* + * User requires wr-protect, and allows silently skipping + * unsupported vmas. + */ + if (p->arg.flags & PM_SCAN_WP_MATCHING) + return 1; + /* + * Then the request doesn't involve wr-protects at all, + * fall through to the rest checks, and allow vma walk. + */ + } if (vma->vm_flags & VM_PFNMAP) return 1; + if (wp_allowed) + vma_category |= PAGE_IS_WPALLOWED; + if (!pagemap_scan_is_interesting_vma(vma_category, p)) return 1; _ Patches currently in -mm which might be from peterx@xxxxxxxxxx are mm-pagemap-fix-ioctlpagemap_scan-on-vma-check.patch mm-pagemap-fix-wr-protect-even-if-pm_scan_wp_matching-not-set.patch mm-selftests-fix-pagemap_ioctl-memory-map-test.patch