From 9a12d103f7d2d524f5e3d4358b9a9c03e4a9f1d2 Mon Sep 17 00:00:00 2001 From: "Liam R. Howlett" Date: Fri, 29 Sep 2023 14:30:41 -0400 Subject: mmap: add clarifying comment to vma_merge() code 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. Link: https://lkml.kernel.org/r/20230929183041.2835469-4-Liam.Howlett@oracle.com Signed-off-by: Liam R. Howlett Suggested-by: Jann Horn Link: https://lore.kernel.org/linux-mm/CAG48ez3iDwFPR=Ed1BfrNuyUJPMK_=StjxhUsCkL6po1s7bONg@mail.gmail.com/ Reviewed-by: Lorenzo Stoakes Acked-by: Vlastimil Babka Cc: Matthew Wilcox (Oracle) Cc: Suren Baghdasaryan Signed-off-by: Andrew Morton --- mm/mmap.c | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'mm/mmap.c') diff --git a/mm/mmap.c b/mm/mmap.c index 011ba48d9e72..673429ee8a9e 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -943,6 +943,11 @@ 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); } -- cgit