From 64b0e0b28508be6c85eccbb0be56a4ee9337639d Mon Sep 17 00:00:00 2001 From: Ryan Roberts Date: Tue, 23 Jan 2024 14:17:55 +0000 Subject: [PATCH] UPSTREAM: mm/userfaultfd: UFFDIO_MOVE implementation should use ptep_get() Commit c33c794828f2 ("mm: ptep_get() conversion") converted all (non-arch) call sites to use ptep_get() instead of doing a direct dereference of the pte. Full rationale can be found in that commit's log. Since then, UFFDIO_MOVE has been implemented which does 7 direct pte dereferences. Let's fix those up to use ptep_get(). I've asserted in the past that there is no reliable automated mechanism to catch these; I'm relying on a combination of Coccinelle (which throws up a lot of false positives) and some compiler magic to force a compiler error on dereference. But given the frequency with which new issues are coming up, I'll add it to my todo list to try to find an automated solution. Bug: 254441685 Link: https://lkml.kernel.org/r/20240123141755.3836179-1-ryan.roberts@arm.com Fixes: adef440691ba ("userfaultfd: UFFDIO_MOVE uABI") Signed-off-by: Ryan Roberts Reviewed-by: Suren Baghdasaryan Cc: Andrea Arcangeli Cc: David Hildenbrand Signed-off-by: Andrew Morton (cherry picked from commit 56ae10cf628b02279980d17439c6241a643959c2) Signed-off-by: Lee Jones Change-Id: I0573208f1c7ad5085e0f7e82d484199074a5f6ef --- mm/userfaultfd.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index dffa3fe756a6..789b78245e9c 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -941,8 +941,8 @@ static int move_present_pte(struct mm_struct *mm, double_pt_lock(dst_ptl, src_ptl); - if (!pte_same(*src_pte, orig_src_pte) || - !pte_same(*dst_pte, orig_dst_pte)) { + if (!pte_same(ptep_get(src_pte), orig_src_pte) || + !pte_same(ptep_get(dst_pte), orig_dst_pte)) { err = -EAGAIN; goto out; } @@ -985,8 +985,8 @@ static int move_swap_pte(struct mm_struct *mm, double_pt_lock(dst_ptl, src_ptl); - if (!pte_same(*src_pte, orig_src_pte) || - !pte_same(*dst_pte, orig_dst_pte)) { + if (!pte_same(ptep_get(src_pte), orig_src_pte) || + !pte_same(ptep_get(dst_pte), orig_dst_pte)) { double_pt_unlock(dst_ptl, src_ptl); return -EAGAIN; } @@ -1085,7 +1085,7 @@ retry: } spin_lock(dst_ptl); - orig_dst_pte = *dst_pte; + orig_dst_pte = ptep_get(dst_pte); spin_unlock(dst_ptl); if (!pte_none(orig_dst_pte)) { err = -EEXIST; @@ -1093,7 +1093,7 @@ retry: } spin_lock(src_ptl); - orig_src_pte = *src_pte; + orig_src_pte = ptep_get(src_pte); spin_unlock(src_ptl); if (pte_none(orig_src_pte)) { if (!(mode & UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES)) @@ -1131,7 +1131,7 @@ retry: * page isn't freed under us */ spin_lock(src_ptl); - if (!pte_same(orig_src_pte, *src_pte)) { + if (!pte_same(orig_src_pte, ptep_get(src_pte))) { spin_unlock(src_ptl); err = -EAGAIN; goto out;