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([2620:10d:c090:400::4:56eb]) by smtp.gmail.com with ESMTPSA id h1-20020a056a00230100b006889511ab14sm3187642pfh.37.2023.11.04.11.28.30 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 04 Nov 2023 11:28:31 -0700 (PDT) Message-ID: <67c45ff3-4f98-4ca5-bd68-2d90cc52a775@davidwei.uk> Date: Sat, 4 Nov 2023 11:28:28 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net v2] virtio/vsock: Fix uninit-value in virtio_transport_recv_pkt() To: Shigeru Yoshida , stefanha@redhat.com, sgarzare@redhat.com, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com Cc: kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+0c8ce1da0ac31abbadcd@syzkaller.appspotmail.com References: <20231104150531.257952-1-syoshida@redhat.com> Content-Language: en-GB From: David Wei In-Reply-To: <20231104150531.257952-1-syoshida@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023-11-04 08:05, Shigeru Yoshida wrote: > KMSAN reported the following uninit-value access issue: > > ===================================================== > BUG: KMSAN: uninit-value in virtio_transport_recv_pkt+0x1dfb/0x26a0 net/vmw_vsock/virtio_transport_common.c:1421 > virtio_transport_recv_pkt+0x1dfb/0x26a0 net/vmw_vsock/virtio_transport_common.c:1421 > vsock_loopback_work+0x3bb/0x5a0 net/vmw_vsock/vsock_loopback.c:120 > process_one_work kernel/workqueue.c:2630 [inline] > process_scheduled_works+0xff6/0x1e60 kernel/workqueue.c:2703 > worker_thread+0xeca/0x14d0 kernel/workqueue.c:2784 > kthread+0x3cc/0x520 kernel/kthread.c:388 > ret_from_fork+0x66/0x80 arch/x86/kernel/process.c:147 > ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304 > > Uninit was stored to memory at: > virtio_transport_space_update net/vmw_vsock/virtio_transport_common.c:1274 [inline] > virtio_transport_recv_pkt+0x1ee8/0x26a0 net/vmw_vsock/virtio_transport_common.c:1415 > vsock_loopback_work+0x3bb/0x5a0 net/vmw_vsock/vsock_loopback.c:120 > process_one_work kernel/workqueue.c:2630 [inline] > process_scheduled_works+0xff6/0x1e60 kernel/workqueue.c:2703 > worker_thread+0xeca/0x14d0 kernel/workqueue.c:2784 > kthread+0x3cc/0x520 kernel/kthread.c:388 > ret_from_fork+0x66/0x80 arch/x86/kernel/process.c:147 > ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304 > > Uninit was created at: > slab_post_alloc_hook+0x105/0xad0 mm/slab.h:767 > slab_alloc_node mm/slub.c:3478 [inline] > kmem_cache_alloc_node+0x5a2/0xaf0 mm/slub.c:3523 > kmalloc_reserve+0x13c/0x4a0 net/core/skbuff.c:559 > __alloc_skb+0x2fd/0x770 net/core/skbuff.c:650 > alloc_skb include/linux/skbuff.h:1286 [inline] > virtio_vsock_alloc_skb include/linux/virtio_vsock.h:66 [inline] > virtio_transport_alloc_skb+0x90/0x11e0 net/vmw_vsock/virtio_transport_common.c:58 > virtio_transport_reset_no_sock net/vmw_vsock/virtio_transport_common.c:957 [inline] > virtio_transport_recv_pkt+0x1279/0x26a0 net/vmw_vsock/virtio_transport_common.c:1387 > vsock_loopback_work+0x3bb/0x5a0 net/vmw_vsock/vsock_loopback.c:120 > process_one_work kernel/workqueue.c:2630 [inline] > process_scheduled_works+0xff6/0x1e60 kernel/workqueue.c:2703 > worker_thread+0xeca/0x14d0 kernel/workqueue.c:2784 > kthread+0x3cc/0x520 kernel/kthread.c:388 > ret_from_fork+0x66/0x80 arch/x86/kernel/process.c:147 > ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304 > > CPU: 1 PID: 10664 Comm: kworker/1:5 Not tainted 6.6.0-rc3-00146-g9f3ebbef746f #3 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-1.fc38 04/01/2014 > Workqueue: vsock-loopback vsock_loopback_work > ===================================================== > > The following simple reproducer can cause the issue described above: > > int main(void) > { > int sock; > struct sockaddr_vm addr = { > .svm_family = AF_VSOCK, > .svm_cid = VMADDR_CID_ANY, > .svm_port = 1234, > }; > > sock = socket(AF_VSOCK, SOCK_STREAM, 0); > connect(sock, (struct sockaddr *)&addr, sizeof(addr)); > return 0; > } > > This issue occurs because the `buf_alloc` and `fwd_cnt` fields of the > `struct virtio_vsock_hdr` are not initialized when a new skb is allocated > in `virtio_transport_init_hdr()`. This patch resolves the issue by > initializing these fields during allocation. > > Fixes: 71dc9ec9ac7d ("virtio/vsock: replace virtio_vsock_pkt with sk_buff") > Reported-and-tested-by: syzbot+0c8ce1da0ac31abbadcd@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=0c8ce1da0ac31abbadcd > Signed-off-by: Shigeru Yoshida > --- > v1->v2: > - Rebase on the latest net tree > https://lore.kernel.org/all/20231026150154.3536433-1-syoshida@redhat.com/ > --- > net/vmw_vsock/virtio_transport_common.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c > index e22c81435ef7..dc65dd4d26df 100644 > --- a/net/vmw_vsock/virtio_transport_common.c > +++ b/net/vmw_vsock/virtio_transport_common.c > @@ -130,6 +130,8 @@ static void virtio_transport_init_hdr(struct sk_buff *skb, > hdr->dst_port = cpu_to_le32(dst_port); > hdr->flags = cpu_to_le32(info->flags); > hdr->len = cpu_to_le32(payload_len); > + hdr->buf_alloc = cpu_to_le32(0); > + hdr->fwd_cnt = cpu_to_le32(0); This change looks good to me. I did notice that payload_len in virtio_transport_init_hdr is size_t but len in struct virtio_vsock_hdr is __le32. But I don't think this is an issue other than wasting some stack space, though. > } > > static void virtio_transport_copy_nonlinear_skb(const struct sk_buff *skb,