Re: [PATCH net-next v6 0/8] fix two bugs related to page_pool

On 2025/1/7 7:51, Jakub Kicinski wrote:

On Mon, 6 Jan 2025 21:01:08 +0800 Yunsheng Lin wrote:

quoted

This patchset fix a possible time window problem for page_pool and
the dma API misuse problem as mentioned in [1], and try to avoid the
overhead of the fixing using some optimization.

From the below performance data, the overhead is not so obvious
due to performance variations for time_bench_page_pool01_fast_path()
and time_bench_page_pool02_ptr_ring, and there is about 20ns overhead
for time_bench_page_pool03_slow() for fixing the bug.

This appears to make the selftest from the drivers/net target implode.

[   20.227775][  T218] BUG: KASAN: use-after-free in page_pool_item_uninit+0x100/0x130

Running the ping.py tests should be enough to repro.

Thanks for reminding.
Something like below seems to fix the use-after-free bug, will enable more
DEBUG config when doing testing.

--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c

@@ -518,9 +518,13 @@ static void page_pool_items_unmap(struct page_pool *pool)

 static void page_pool_item_uninit(struct page_pool *pool)
 {
-       struct page_pool_item_block *block;
+       while (!list_empty(&pool->item_blocks)) {
+               struct page_pool_item_block *block;

-       list_for_each_entry(block, &pool->item_blocks, list) {
+               block = list_first_entry(&pool->item_blocks,
+                                        struct page_pool_item_block,
+                                        list);
+               list_del(&block->list);
                WARN_ON(refcount_read(&block->ref));
                put_page(virt_to_page(block));
        }