From d70cec8983241a6aafadf78e2d65bbafac87ab6a Mon Sep 17 00:00:00 2001 From: Miaohe Lin Date: Thu, 6 Aug 2020 23:23:34 -0700 Subject: [PATCH] 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 Signed-off-by: Miaohe Lin Signed-off-by: Andrew Morton Reviewed-by: Andrew Morton Link: http://lkml.kernel.org/r/1594954065-23733-1-git-send-email-linmiaohe@huawei.com Signed-off-by: Linus Torvalds --- mm/mmap.c | 22 +++++++++++++++++++++- 1 file changed, 21 insertions(+), 1 deletion(-) 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)