diff options
| author | Dmitry Safonov <[email protected]> | 2020-12-14 19:08:21 -0800 |
|---|---|---|
| committer | Linus Torvalds <[email protected]> | 2020-12-15 12:13:41 -0800 |
| commit | 73d5e06299195f4df82832cfc4a3a0c574c1e473 (patch) | |
| tree | d2923cc106b9f374e309b8760e4e5d9927b998fd | |
| parent | dd3b614f858d88f33e0cf8b7353e2ad937e71da3 (diff) | |
mremap: check if it's possible to split original vma
If original VMA can't be split at the desired address, do_munmap() will
fail and leave both new-copied VMA and old VMA. De-facto it's
MREMAP_DONTUNMAP behaviour, which is unexpected.
Currently, it may fail such way for hugetlbfs and dax device mappings.
Minimize such unpleasant situations to OOM by checking .may_split() before
attempting to create a VMA copy.
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Dmitry Safonov <[email protected]>
Cc: Alexander Viro <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Brian Geffon <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Dan Carpenter <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Dave Jiang <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jason Gunthorpe <[email protected]>
Cc: John Hubbard <[email protected]>
Cc: "Kirill A. Shutemov" <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: Ralph Campbell <[email protected]>
Cc: Russell King <[email protected]>
Cc: Thomas Bogendoerfer <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Vishal Verma <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Will Deacon <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
| -rw-r--r-- | mm/mremap.c | 11 |
1 files changed, 10 insertions, 1 deletions
diff --git a/mm/mremap.c b/mm/mremap.c index 366b3dea992c..c5590afe7165 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -493,7 +493,7 @@ static unsigned long move_vma(struct vm_area_struct *vma, unsigned long excess = 0; unsigned long hiwater_vm; int split = 0; - int err; + int err = 0; bool need_rmap_locks; /* @@ -503,6 +503,15 @@ static unsigned long move_vma(struct vm_area_struct *vma, if (mm->map_count >= sysctl_max_map_count - 3) return -ENOMEM; + if (vma->vm_ops && vma->vm_ops->may_split) { + if (vma->vm_start != old_addr) + err = vma->vm_ops->may_split(vma, old_addr); + if (!err && vma->vm_end != old_addr + old_len) + err = vma->vm_ops->may_split(vma, old_addr + old_len); + if (err) + return err; + } + /* * Advise KSM to break any KSM pages in the area to be moved: * it would be confusing if they were to turn up at the new |