Re: [PATCH net] page_pool: Fix use-after-free in page_pool_recycle_in_ring

["Toke Høiland-Jørgensen" <toke@redhat.com>]

Dong Chenchen <dongchenchen2@huawei.com> writes:

> syzbot reported a uaf in page_pool_recycle_in_ring:
>
> BUG: KASAN: slab-use-after-free in lock_release+0x151/0xa30 kernel/locking/lockdep.c:5862
> Read of size 8 at addr ffff8880286045a0 by task syz.0.284/6943
>
> CPU: 0 UID: 0 PID: 6943 Comm: syz.0.284 Not tainted 6.13.0-rc3-syzkaller-gdfa94ce54f41 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:94 [inline]
>  dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
>  print_address_description mm/kasan/report.c:378 [inline]
>  print_report+0x169/0x550 mm/kasan/report.c:489
>  kasan_report+0x143/0x180 mm/kasan/report.c:602
>  lock_release+0x151/0xa30 kernel/locking/lockdep.c:5862
>  __raw_spin_unlock_bh include/linux/spinlock_api_smp.h:165 [inline]
>  _raw_spin_unlock_bh+0x1b/0x40 kernel/locking/spinlock.c:210
>  spin_unlock_bh include/linux/spinlock.h:396 [inline]
>  ptr_ring_produce_bh include/linux/ptr_ring.h:164 [inline]
>  page_pool_recycle_in_ring net/core/page_pool.c:707 [inline]
>  page_pool_put_unrefed_netmem+0x748/0xb00 net/core/page_pool.c:826
>  page_pool_put_netmem include/net/page_pool/helpers.h:323 [inline]
>  page_pool_put_full_netmem include/net/page_pool/helpers.h:353 [inline]
>  napi_pp_put_page+0x149/0x2b0 net/core/skbuff.c:1036
>  skb_pp_recycle net/core/skbuff.c:1047 [inline]
>  skb_free_head net/core/skbuff.c:1094 [inline]
>  skb_release_data+0x6c4/0x8a0 net/core/skbuff.c:1125
>  skb_release_all net/core/skbuff.c:1190 [inline]
>  __kfree_skb net/core/skbuff.c:1204 [inline]
>  sk_skb_reason_drop+0x1c9/0x380 net/core/skbuff.c:1242
>  kfree_skb_reason include/linux/skbuff.h:1263 [inline]
>  __skb_queue_purge_reason include/linux/skbuff.h:3343 [inline]
>
> root cause is:
>
> page_pool_recycle_in_ring
>   ptr_ring_produce
>     spin_lock(&r->producer_lock);
>     WRITE_ONCE(r->queue[r->producer++], ptr)
>       //recycle last page to pool
> 				page_pool_release
> 				  page_pool_scrub
> 				    page_pool_empty_ring
> 				      ptr_ring_consume
> 				      page_pool_return_page  //release all page
> 				  __page_pool_destroy
> 				     free_percpu(pool->recycle_stats);
> 				     free(pool) //free
>
>      spin_unlock(&r->producer_lock); //pool->ring uaf read
>   recycle_stat_inc(pool, ring);
>
> page_pool can be free while page pool recycle the last page in ring.
> Add producer-lock barrier to page_pool_release to prevent the page
> pool from being free before all pages have been recycled.
>
> Suggested-by: Jakub Kacinski <kuba@kernel.org>
> Link: https://lore.kernel.org/netdev/20250513083123.3514193-1-dongchenchen2@huawei.com
> Fixes: ff7d6b27f894 ("page_pool: refurbish version of page_pool code")
> Reported-by: syzbot+204a4382fcb3311f3858@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=204a4382fcb3311f3858
> Signed-off-by: Dong Chenchen <dongchenchen2@huawei.com>

Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>