diff options
| author | David Hildenbrand <david@redhat.com> | 2022-11-16 11:26:44 +0100 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2022-11-30 15:58:57 -0800 |
| commit | 79881fed6052a9ce00cfb63297832b9faacf8cf3 (patch) | |
| tree | f92550ecfc810fb06a31163d848ffaaceff0f5eb /mm | |
| parent | cdc5021cda194112bc0962d6a0e90b379968c504 (diff) | |
| download | linux-79881fed6052a9ce00cfb63297832b9faacf8cf3.tar.bz2 | |
mm: add early FAULT_FLAG_WRITE consistency checks
Let's catch abuse of FAULT_FLAG_WRITE early, such that we don't have to
care in all other handlers and might get "surprises" if we forget to do
so.
Write faults without VM_MAYWRITE don't make any sense, and our
maybe_mkwrite() logic could have hidden such abuse for now.
Write faults without VM_WRITE on something that is not a COW mapping is
similarly broken, and e.g., do_wp_page() could end up placing an
anonymous page into a shared mapping, which would be bad.
This is a preparation for reliable R/O long-term pinning of pages in
private mappings, whereby we want to make sure that we will never break
COW in a read-only private mapping.
Link: https://lkml.kernel.org/r/20221116102659.70287-6-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/memory.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/mm/memory.c b/mm/memory.c index 07380ef935ac..5e4df6b87016 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -5170,6 +5170,14 @@ static vm_fault_t sanitize_fault_flags(struct vm_area_struct *vma, */ if (!is_cow_mapping(vma->vm_flags)) *flags &= ~FAULT_FLAG_UNSHARE; + } else if (*flags & FAULT_FLAG_WRITE) { + /* Write faults on read-only mappings are impossible ... */ + if (WARN_ON_ONCE(!(vma->vm_flags & VM_MAYWRITE))) + return VM_FAULT_SIGSEGV; + /* ... and FOLL_FORCE only applies to COW mappings. */ + if (WARN_ON_ONCE(!(vma->vm_flags & VM_WRITE) && + !is_cow_mapping(vma->vm_flags))) + return VM_FAULT_SIGSEGV; } return 0; } |