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BACKPORT: FROMGIT: mm: always lock new vma before inserting into vma tree

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While it's not strictly necessary to lock a newly created vma before
adding it into the vma tree (as long as no further changes are performed
to it), it seems like a good policy to lock it and prevent accidental
changes after it becomes visible to the page faults. Lock the vma before
adding it into the vma tree.

Link: https://lkml.kernel.org/r/20230804152724.3090321-6-surenb@google.com
Suggested-by: Jann Horn <jannh@google.com>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Linus Torvalds <torvalds@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

(cherry picked from commit c3249c06c48dda30f93e62b57773d5ed409d4f77
https: //git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-unstable)
[surenb: resolved conflicts due to changes in vma_merge() and
__vma_adjust()]

Bug: 293665307
Change-Id: I4ee0d2abcc8a3f45545f470f1bf7f0be728d6f44
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
This commit is contained in:
Suren Baghdasaryan 2023-08-04 08:27:23 -07:00
parent a8a479ed96
commit 0f0b09c02c
1 changed files with 7 additions and 2 deletions
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9
mm/mmap.c
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@ -484,6 +484,8 @@ static int vma_link(struct mm_struct *mm, struct vm_area_struct *vma)
if (mas_preallocate(&mas, vma, GFP_KERNEL))
return -ENOMEM;
vma_start_write(vma);
if (vma->vm_file) {
mapping = vma->vm_file->f_mapping;
i_mmap_lock_write(mapping);
@ -744,8 +746,10 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
if (adjust_next < 0)
mas_set_range(&mas, next->vm_start + adjust_next,
next->vm_end - 1);
else if (insert)
else if (insert) {
vma_start_write(insert);
mas_set_range(&mas, insert->vm_start, insert->vm_end - 1);
}
if (mas_preallocate(&mas, vma, GFP_KERNEL))
@ -843,6 +847,7 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
* (it may either follow vma or precede it).
*/
mas_reset(&mas);
vma_start_write(insert);
vma_mas_store(insert, &mas);
mm->map_count++;
}
@ -3204,6 +3209,7 @@ static int do_brk_flags(struct ma_state *mas, struct vm_area_struct *vma,
vma->vm_pgoff = addr >> PAGE_SHIFT;
vm_flags_init(vma, flags);
vma->vm_page_prot = vm_get_page_prot(flags);
vma_start_write(vma);
mas_set_range(mas, vma->vm_start, addr + len - 1);
if (mas_store_gfp(mas, vma, GFP_KERNEL))
goto mas_store_fail;
@ -3450,7 +3456,6 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
get_file(new_vma->vm_file);
if (new_vma->vm_ops && new_vma->vm_ops->open)
new_vma->vm_ops->open(new_vma);
vma_start_write(new_vma);
if (vma_link(mm, new_vma))
goto out_vma_link;
*need_rmap_locks = false;