From: Eric Dumazet edumazet@google.com
[ Upstream commit 1efba987c48629c0c64703bb4ea76ca1a3771d17 ]
If both IFF_NAPI_FRAGS mode and XDP are enabled, and the XDP program consumes the skb, we need to clear the napi.skb (or risk a use-after-free) and release the mutex (or risk a deadlock)
WARNING: lock held when returning to user space! 5.5.0-rc6-syzkaller #0 Not tainted ------------------------------------------------ syz-executor.0/455 is leaving the kernel with locks still held! 1 lock held by syz-executor.0/455: #0: ffff888098f6e748 (&tfile->napi_mutex){+.+.}, at: tun_get_user+0x1604/0x3fc0 drivers/net/tun.c:1835
Fixes: 90e33d459407 ("tun: enable napi_gro_frags() for TUN/TAP driver") Signed-off-by: Eric Dumazet edumazet@google.com Reported-by: syzbot syzkaller@googlegroups.com Cc: Petar Penkov ppenkov@google.com Cc: Willem de Bruijn willemb@google.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/tun.c | 4 ++++ 1 file changed, 4 insertions(+)
--- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -1936,6 +1936,10 @@ drop: if (ret != XDP_PASS) { rcu_read_unlock(); local_bh_enable(); + if (frags) { + tfile->napi.skb = NULL; + mutex_unlock(&tfile->napi_mutex); + } return total_len; } }