diff options
| author | Miaohe Lin <linmiaohe@huawei.com> | 2020-08-06 23:23:34 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-08-07 11:33:27 -0700 |
| commit | d70cec8983241a6aafadf78e2d65bbafac87ab6a (patch) | |
| tree | c8b3cafa4ce9f3d7df68b0396a87eb6c6841949f /mm/mmap.c | |
| parent | eee07935bb52a03561d53ccc5cecf12f2faeb396 (diff) | |
mm: mmap: merge vma after call_mmap() if possible
The vm_flags may be changed after call_mmap() because drivers may set some
flags for their own purpose. As a result, we failed to merge the adjacent
vma due to the different vm_flags as userspace can't pass in the same one.
Try to merge vma after call_mmap() to fix this issue.
Signed-off-by: Hongxiang Lou <louhongxiang@huawei.com>
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/1594954065-23733-1-git-send-email-linmiaohe@huawei.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/mmap.c')
| -rw-r--r-- | mm/mmap.c | 22 |
1 files changed, 21 insertions, 1 deletions
diff --git a/mm/mmap.c b/mm/mmap.c index 853ae3aebc3d..ba39409cdb17 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1690,7 +1690,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr, struct list_head *uf) { struct mm_struct *mm = current->mm; - struct vm_area_struct *vma, *prev; + struct vm_area_struct *vma, *prev, *merge; int error; struct rb_node **rb_link, *rb_parent; unsigned long charged = 0; @@ -1774,6 +1774,25 @@ unsigned long mmap_region(struct file *file, unsigned long addr, if (error) goto unmap_and_free_vma; + /* If vm_flags changed after call_mmap(), we should try merge vma again + * as we may succeed this time. + */ + if (unlikely(vm_flags != vma->vm_flags && prev)) { + merge = vma_merge(mm, prev, vma->vm_start, vma->vm_end, vma->vm_flags, + NULL, vma->vm_file, vma->vm_pgoff, NULL, NULL_VM_UFFD_CTX); + if (merge) { + fput(file); + vm_area_free(vma); + vma = merge; + /* Update vm_flags and possible addr to pick up the change. We don't + * warn here if addr changed as the vma is not linked by vma_link(). + */ + addr = vma->vm_start; + vm_flags = vma->vm_flags; + goto unmap_writable; + } + } + /* Can addr have changed?? * * Answer: Yes, several device drivers can do it in their @@ -1796,6 +1815,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr, vma_link(mm, vma, prev, rb_link, rb_parent); /* Once vma denies write, undo our temporary denial count */ if (file) { +unmap_writable: if (vm_flags & VM_SHARED) mapping_unmap_writable(file->f_mapping); if (vm_flags & VM_DENYWRITE) |