From 635e92cfe1ac6b4e0806c08a59d575d5562adccd Mon Sep 17 00:00:00 2001 From: John Fastabend Date: Fri, 24 May 2019 08:01:00 -0700 Subject: [PATCH] bpf: sockmap, fix use after free from sleep in psock backlog workqueue [ Upstream commit bd95e678e0f6e18351ecdc147ca819145db9ed7b ] Backlog work for psock (sk_psock_backlog) might sleep while waiting for memory to free up when sending packets. However, while sleeping the socket may be closed and removed from the map by the user space side. This breaks an assumption in sk_stream_wait_memory, which expects the wait queue to be still there when it wakes up resulting in a use-after-free shown below. To fix his mark sendmsg as MSG_DONTWAIT to avoid the sleep altogether. We already set the flag for the sendpage case but we missed the case were sendmsg is used. Sockmap is currently the only user of skb_send_sock_locked() so only the sockmap paths should be impacted. ================================================================== BUG: KASAN: use-after-free in remove_wait_queue+0x31/0x70 Write of size 8 at addr ffff888069a0c4e8 by task kworker/0:2/110 CPU: 0 PID: 110 Comm: kworker/0:2 Not tainted 5.0.0-rc2-00335-g28f9d1a3d4fe-dirty #14 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-2.fc27 04/01/2014 Workqueue: events sk_psock_backlog Call Trace: print_address_description+0x6e/0x2b0 ? remove_wait_queue+0x31/0x70 kasan_report+0xfd/0x177 ? remove_wait_queue+0x31/0x70 ? remove_wait_queue+0x31/0x70 remove_wait_queue+0x31/0x70 sk_stream_wait_memory+0x4dd/0x5f0 ? sk_stream_wait_close+0x1b0/0x1b0 ? wait_woken+0xc0/0xc0 ? tcp_current_mss+0xc5/0x110 tcp_sendmsg_locked+0x634/0x15d0 ? tcp_set_state+0x2e0/0x2e0 ? __kasan_slab_free+0x1d1/0x230 ? kmem_cache_free+0x70/0x140 ? sk_psock_backlog+0x40c/0x4b0 ? process_one_work+0x40b/0x660 ? worker_thread+0x82/0x680 ? kthread+0x1b9/0x1e0 ? ret_from_fork+0x1f/0x30 ? check_preempt_curr+0xaf/0x130 ? iov_iter_kvec+0x5f/0x70 ? kernel_sendmsg_locked+0xa0/0xe0 skb_send_sock_locked+0x273/0x3c0 ? skb_splice_bits+0x180/0x180 ? start_thread+0xe0/0xe0 ? update_min_vruntime.constprop.27+0x88/0xc0 sk_psock_backlog+0xb3/0x4b0 ? strscpy+0xbf/0x1e0 process_one_work+0x40b/0x660 worker_thread+0x82/0x680 ? process_one_work+0x660/0x660 kthread+0x1b9/0x1e0 ? __kthread_create_on_node+0x250/0x250 ret_from_fork+0x1f/0x30 Fixes: 20bf50de3028c ("skbuff: Function to send an skbuf on a socket") Reported-by: Jakub Sitnicki Tested-by: Jakub Sitnicki Signed-off-by: John Fastabend Signed-off-by: Daniel Borkmann Signed-off-by: Sasha Levin --- net/core/skbuff.c | 1 + 1 file changed, 1 insertion(+) diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 2b3b0307dd89..6d9fd7d4bdfa 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -2299,6 +2299,7 @@ do_frag_list: kv.iov_base = skb->data + offset; kv.iov_len = slen; memset(&msg, 0, sizeof(msg)); + msg.msg_flags = MSG_DONTWAIT; ret = kernel_sendmsg_locked(sk, &msg, &kv, 1, slen); if (ret <= 0) -- 2.20.1