On Thu, Jan 25, 2024 at 10:33:17AM +0000, Eric Dumazet wrote:
> +++ b/net/ipv4/tcp.c
> @@ -1786,7 +1786,17 @@ static skb_frag_t *skb_advance_to_frag(struct sk_buff *skb, u32 offset_skb,
>
> static bool can_map_frag(const skb_frag_t *frag)
> {
> - return skb_frag_size(frag) == PAGE_SIZE && !skb_frag_off(frag);
> + struct page *page;
> +
> + if (skb_frag_size(frag) != PAGE_SIZE || skb_frag_off(frag))
> + return false;
> +
> + page = skb_frag_page(frag);
> +
> + if (PageCompound(page) || page->mapping)
> + return false;
I'm not entirely sure why you're testing PageCompound here. If a driver
allocates a compound page, we'd still want to be able to insert it,
right?
I have a feeling that we want to fix this in the VM layer. There are
some weird places calling vm_insert_page() and we should probably make
them all fail.
Something like this, perhaps?
diff --git a/mm/memory.c b/mm/memory.c
index 1a60faad2e49..ae0abab56d38 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1871,6 +1871,10 @@ static int insert_page_into_pte_locked(struct vm_area_struct *vma, pte_t *pte,
if (!pte_none(ptep_get(pte)))
return -EBUSY;
+ if (folio->mapping &&
+ ((addr - vma->vm_start) / PAGE_SIZE + vma->vm_pgoff) !=
+ (folio->index + folio_page_idx(folio, page)))
+ return -EINVAL;
/* Ok, finally just insert the thing.. */
folio_get(folio);
inc_mm_counter(vma->vm_mm, mm_counter_file(folio));
