From: Dong Chenchen dongchenchen2@huawei.com

[ Upstream commit 271683bb2cf32e5126c592b5d5e6a756fa374fd9 ]

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 Kicinski kuba@kernel.org Link: https://lore.kernel.org/netdev/20250513083123.3514193-1-dongchenchen2@huawei... 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 Link: https://patch.msgid.link/20250527114152.3119109-1-dongchenchen2@huawei.com Signed-off-by: Jakub Kicinski kuba@kernel.org [ Linux 5.15.y does not support page pool statistics (CONFIG_PAGE_POOL_STATS), so remove the related source code changes from the patch. ] Signed-off-by: Ruohan Lan ruohanlan@aliyun.com --- net/core/page_pool.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/net/core/page_pool.c b/net/core/page_pool.c index 4ec7e6229f69..b3047197a5e8 100644 --- a/net/core/page_pool.c +++ b/net/core/page_pool.c @@ -414,14 +414,14 @@ static void page_pool_return_page(struct page_pool *pool, struct page *page)

static bool page_pool_recycle_in_ring(struct page_pool *pool, struct page *page) { - int ret; + bool in_softirq, ret; + /* BH protection not needed if current is softirq */ - if (in_softirq()) - ret = ptr_ring_produce(&pool->ring, page); - else - ret = ptr_ring_produce_bh(&pool->ring, page); + in_softirq = page_pool_producer_lock(pool); + ret = !__ptr_ring_produce(&pool->ring, page); + page_pool_producer_unlock(pool, in_softirq);

- return (ret == 0) ? true : false; + return ret; }

/* Only allow direct recycling in special circumstances, into the @@ -684,10 +684,14 @@ 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); + /* 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_free(pool);