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| author | Peter Xu <peterx@redhat.com> | 2023-01-04 23:52:07 +0100 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2023-01-19 02:12:53 +0100 |
| commit | d1751118c88673fe5a948ad82277898e9e284c55 (patch) | |
| tree | 9a7e10d925430d407a1ca1444b2b2ee15afc66ca /mm/userfaultfd.c | |
| parent | mm/mprotect: use long for page accountings and retval (diff) | |
| download | linux-d1751118c88673fe5a948ad82277898e9e284c55.tar.xz linux-d1751118c88673fe5a948ad82277898e9e284c55.zip | |
mm/uffd: detect pgtable allocation failures
Before this patch, when there's any pgtable allocation issues happened
during change_protection(), the error will be ignored from the syscall.
For shmem, there will be an error dumped into the host dmesg. Two issues
with that:
(1) Doing a trace dump when allocation fails is not anything close to
grace.
(2) The user should be notified with any kind of such error, so the user
can trap it and decide what to do next, either by retrying, or stop
the process properly, or anything else.
For userfault users, this will change the API of UFFDIO_WRITEPROTECT when
pgtable allocation failure happened. It should not normally break anyone,
though. If it breaks, then in good ways.
One man-page update will be on the way to introduce the new -ENOMEM for
UFFDIO_WRITEPROTECT. Not marking stable so we keep the old behavior on
the 5.19-till-now kernels.
[akpm@linux-foundation.org: coding-style cleanups]
Link: https://lkml.kernel.org/r/20230104225207.1066932-4-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Reported-by: James Houghton <jthoughton@google.com>
Acked-by: James Houghton <jthoughton@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/userfaultfd.c')
| -rw-r--r-- | mm/userfaultfd.c | 16 |
1 files changed, 11 insertions, 5 deletions
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 65ad172add27..53c3d916ff66 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -710,11 +710,12 @@ ssize_t mcopy_continue(struct mm_struct *dst_mm, unsigned long start, mmap_changing, 0); } -void uffd_wp_range(struct mm_struct *dst_mm, struct vm_area_struct *dst_vma, +long uffd_wp_range(struct mm_struct *dst_mm, struct vm_area_struct *dst_vma, unsigned long start, unsigned long len, bool enable_wp) { unsigned int mm_cp_flags; struct mmu_gather tlb; + long ret; if (enable_wp) mm_cp_flags = MM_CP_UFFD_WP; @@ -730,8 +731,10 @@ void uffd_wp_range(struct mm_struct *dst_mm, struct vm_area_struct *dst_vma, if (!enable_wp && vma_wants_manual_pte_write_upgrade(dst_vma)) mm_cp_flags |= MM_CP_TRY_CHANGE_WRITABLE; tlb_gather_mmu(&tlb, dst_mm); - change_protection(&tlb, dst_vma, start, start + len, mm_cp_flags); + ret = change_protection(&tlb, dst_vma, start, start + len, mm_cp_flags); tlb_finish_mmu(&tlb); + + return ret; } int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start, @@ -740,7 +743,7 @@ int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start, { struct vm_area_struct *dst_vma; unsigned long page_mask; - int err; + long err; /* * Sanitize the command parameters: @@ -779,9 +782,12 @@ int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start, goto out_unlock; } - uffd_wp_range(dst_mm, dst_vma, start, len, enable_wp); + err = uffd_wp_range(dst_mm, dst_vma, start, len, enable_wp); + + /* Return 0 on success, <0 on failures */ + if (err > 0) + err = 0; - err = 0; out_unlock: mmap_read_unlock(dst_mm); return err; |