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Message-ID: <CANn89i+Y1_GesZ+Afh3SXkYR_Bux-HUALkoh6WJ47YkGHgZaRg@mail.gmail.com> Date: Fri, 27 Oct 2023 10:50:50 +0200 From: Eric Dumazet <edumazet@...gle.com> To: Stefano Garzarella <sgarzare@...hat.com> Cc: Shigeru Yoshida <syoshida@...hat.com>, stefanha@...hat.com, davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com, kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, bobby.eshleman@...edance.com, bobbyeshleman@...il.com Subject: Re: [PATCH net] virtio/vsock: Fix uninit-value in virtio_transport_recv_pkt() On Fri, Oct 27, 2023 at 10:18 AM Stefano Garzarella <sgarzare@...hat.com> wrote: > > On Fri, Oct 27, 2023 at 10:01 AM Stefano Garzarella <sgarzare@...hat.com> wrote: > > > > On Fri, Oct 27, 2023 at 12:01:54AM +0900, 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_alloc_skb()`. This patch resolves the issue by > > >initializing these fields during allocation. > > > > > >Fixes: 71dc9ec9ac7d ("virtio/vsock: replace virtio_vsock_pkt with sk_buff") > > > > CCin Bobby, the original author, for any additional comments/checks. > > > > Yeah, I see, before that commit we used kzalloc() to allocate the > > header so we forgot to reset these 2 fields, and checking they are > > the only 2 missing. > > > > I was thinking of putting a memset(hdr, 0, sizeof(*hdr)) in > > virtio_vsock_alloc_skb() but I think it's just extra unnecessary work, > > since here we set all the fields (thanks to this fix), in vhost/vsock.c > > we copy all the header we receive from the guest and in > > virtio_transport.c we already set it all to 0 because we are > > preallocating the receive buffers. > > > > So I'm fine with this fix! > > > > >Signed-off-by: Shigeru Yoshida <syoshida@...hat.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 352d042b130b..102673bef189 100644 > > >--- a/net/vmw_vsock/virtio_transport_common.c > > >+++ b/net/vmw_vsock/virtio_transport_common.c > > >@@ -68,6 +68,8 @@ virtio_transport_alloc_skb(struct virtio_vsock_pkt_info *info, > > > hdr->dst_port = cpu_to_le32(dst_port); > > > hdr->flags = cpu_to_le32(info->flags); > > > hdr->len = cpu_to_le32(len); > > >+ hdr->buf_alloc = cpu_to_le32(0); > > >+ hdr->fwd_cnt = cpu_to_le32(0); > > > > > > if (info->msg && len > 0) { > > > payload = skb_put(skb, len); > > >-- > > >2.41.0 > > > > > > > Reviewed-by: Stefano Garzarella <sgarzare@...hat.com> > > syzbot just reported the same [1], should we add the following tag? > > Reported-by: syzbot+0c8ce1da0ac31abbadcd@...kaller.appspotmail.com > > [1] https://lore.kernel.org/netdev/00000000000008b2940608ae3ce9@google.com/ Yes, I was about to add this tag as well, but you were fast ;) Reviewed-by: Eric Dumazet <edumazet@...gle.com>
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