[PATCH net v2] page_pool: Fix use-after-free in page_pool_recycle_in_ring

[Dong Chenchen <dongchenchen2@huawei.com>]

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.

recycle_stat_inc() is empty when CONFIG_PAGE_POOL_STATS is not
enabled, which will trigger Wempty-body build warning. Add definition
for pool stat macro to fix warning.

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>
Reviewed-by: Mina Almasry <almasrymina@google.com>
---
Changes in v2:
 - Change the return type from int to bool
 - Fix Wempty-body warn of recycle_stat_inc
---
 net/core/page_pool.c | 27 ++++++++++++++-------------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index 7745ad924ae2..862ec1dc48df 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -153,9 +153,9 @@ u64 *page_pool_ethtool_stats_get(u64 *data, const void *stats)
 EXPORT_SYMBOL(page_pool_ethtool_stats_get);
 
 #else
-#define alloc_stat_inc(pool, __stat)
-#define recycle_stat_inc(pool, __stat)
-#define recycle_stat_add(pool, __stat, val)
+#define alloc_stat_inc(...)	do { } while (0)
+#define recycle_stat_inc(...)	do { } while (0)
+#define recycle_stat_add(...)	do { } while (0)
 #endif
 
 static bool page_pool_producer_lock(struct page_pool *pool)
@@ -707,19 +707,16 @@ void page_pool_return_page(struct page_pool *pool, netmem_ref netmem)
 
 static bool page_pool_recycle_in_ring(struct page_pool *pool, netmem_ref netmem)
 {
-	int ret;
-	/* BH protection not needed if current is softirq */
-	if (in_softirq())
-		ret = ptr_ring_produce(&pool->ring, (__force void *)netmem);
-	else
-		ret = ptr_ring_produce_bh(&pool->ring, (__force void *)netmem);
+	bool in_softirq, ret;
 
-	if (!ret) {
+	/* BH protection not needed if current is softirq */
+	in_softirq = page_pool_producer_lock(pool);
+	ret = !__ptr_ring_produce(&pool->ring, (__force void *)netmem);
+	if (ret)
 		recycle_stat_inc(pool, ring);
-		return true;
-	}
+	page_pool_producer_unlock(pool, in_softirq);
 
-	return false;
+	return ret;
 }
 
 /* Only allow direct recycling in special circumstances, into the
@@ -1091,10 +1088,14 @@ static void page_pool_scrub(struct page_pool *pool)
 
 static int page_pool_release(struct page_pool *pool)
 {
+	bool in_softirq;
 	int inflight;
 
 	page_pool_scrub(pool);
 	inflight = page_pool_inflight(pool, true);
+	/* Acquire producer lock to make sure producers have exited. */
+	in_softirq = page_pool_producer_lock(pool);
+	page_pool_producer_unlock(pool, in_softirq);
 	if (!inflight)
 		__page_pool_destroy(pool);
 
-- 
2.25.1