On 9/28/23 19:16, Liam R. Howlett wrote: > When tracing through the code in vma_merge(), it was not completely > clear why the error return to a dup_anon_vma() call would not overwrite > a previous attempt to the same function. This commit adds a comment > specifying why it is safe. > > Suggested-by: Jann Horn <jannh@xxxxxxxxxx> > Link: https://lore.kernel.org/linux-mm/CAG48ez3iDwFPR=Ed1BfrNuyUJPMK_=StjxhUsCkL6po1s7bONg@xxxxxxxxxxxxxx/ > Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx> Acked-by: Vlastimil Babka <vbabka@xxxxxxx> > --- > mm/mmap.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/mm/mmap.c b/mm/mmap.c > index 2f0ee489db8a..3c78afb707cf 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -937,6 +937,11 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, > vma_start_write(curr); > remove = curr; > remove2 = next; > + /* > + * Note that the dup_anon_vma below cannot overwrite err > + * since the first caller would do nothing unless next > + * has an anon_vma. > + */ > if (!next->anon_vma) > err = dup_anon_vma(prev, curr, &anon_dup); > }
