From d239462787b072c78eb19fc1f155c3d411256282 Mon Sep 17 00:00:00 2001 From: Anthony Yznaga Date: Tue, 10 Mar 2026 08:58:20 -0700 Subject: mm: prevent droppable mappings from being locked Droppable mappings must not be lockable. There is a check for VMAs with VM_DROPPABLE set in mlock_fixup() along with checks for other types of unlockable VMAs which ensures this when calling mlock()/mlock2(). For mlockall(MCL_FUTURE), the check for unlockable VMAs is different. In apply_mlockall_flags(), if the flags parameter has MCL_FUTURE set, the current task's mm's default VMA flag field mm->def_flags has VM_LOCKED applied to it. VM_LOCKONFAULT is also applied if MCL_ONFAULT is also set. When these flags are set as default in this manner they are cleared in __mmap_complete() for new mappings that do not support mlock. A check for VM_DROPPABLE in __mmap_complete() is missing resulting in droppable mappings created with VM_LOCKED set. To fix this and reduce that chance of similar bugs in the future, introduce and use vma_supports_mlock(). Link: https://lkml.kernel.org/r/20260310155821.17869-1-anthony.yznaga@oracle.com Fixes: 9651fcedf7b9 ("mm: add MAP_DROPPABLE for designating always lazily freeable mappings") Signed-off-by: Anthony Yznaga Suggested-by: David Hildenbrand Acked-by: David Hildenbrand (Arm) Reviewed-by: Pedro Falcato Reviewed-by: Lorenzo Stoakes (Oracle) Tested-by: Lorenzo Stoakes (Oracle) Cc: Jann Horn Cc: Jason A. Donenfeld Cc: Liam Howlett Cc: Michal Hocko Cc: Mike Rapoport Cc: Shuah Khan Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Signed-off-by: Andrew Morton --- tools/testing/vma/include/stubs.h | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'tools') diff --git a/tools/testing/vma/include/stubs.h b/tools/testing/vma/include/stubs.h index 947a3a0c2566..416bb93f5005 100644 --- a/tools/testing/vma/include/stubs.h +++ b/tools/testing/vma/include/stubs.h @@ -426,3 +426,8 @@ static inline void vma_adjust_trans_huge(struct vm_area_struct *vma, } static inline void hugetlb_split(struct vm_area_struct *, unsigned long) {} + +static inline bool vma_supports_mlock(const struct vm_area_struct *vma) +{ + return false; +} -- cgit v1.2.3