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Howlett" To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Jann Horn , Lorenzo Stoakes , Vlastimil Babka , Suren Baghdasaryan , Matthew Wilcox , "Liam R. 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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 Link: https://lore.kernel.org/linux-mm/CAG48ez3iDwFPR=Ed1BfrNuyUJPMK_=StjxhUsCkL6po1s7bONg@mail.gmail.com/ Signed-off-by: Liam R. Howlett Reviewed-by: Lorenzo Stoakes Acked-by: Vlastimil Babka --- mm/mmap.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/mm/mmap.c b/mm/mmap.c index f9f0a5fe4db4..9967acbd070f 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); }