linux.git/net/vmw_vsock, branch v5.10 Linux kernel source tree vsock/virtio: discard packets only when socket is really closed 2020-11-24T00:36:29+00:00 Stefano Garzarella sgarzare@redhat.com 2020-11-20T10:47:36+00:00 3fe356d58efae54dade9ec94ea7c919ed20cf4db Starting from commit 8692cefc433f ("virtio_vsock: Fix race condition in virtio_transport_recv_pkt"), we discard packets in virtio_transport_recv_pkt() if the socket has been released. When the socket is connected, we schedule a delayed work to wait the RST packet from the other peer, also if SHUTDOWN_MASK is set in sk->sk_shutdown. This is done to complete the virtio-vsock shutdown algorithm, releasing the port assigned to the socket definitively only when the other peer has consumed all the packets. If we discard the RST packet received, the socket will be closed only when the VSOCK_CLOSE_TIMEOUT is reached. Sergio discovered the issue while running ab(1) HTTP benchmark using libkrun [1] and observing a latency increase with that commit. To avoid this issue, we discard packet only if the socket is really closed (SOCK_DONE flag is set). We also set SOCK_DONE in virtio_transport_release() when we don't need to wait any packets from the other peer (we didn't schedule the delayed work). In this case we remove the socket from the vsock lists, releasing the port assigned. [1] https://github.com/containers/libkrun Fixes: 8692cefc433f ("virtio_vsock: Fix race condition in virtio_transport_recv_pkt") Cc: justin.he@arm.com Reported-by: Sergio Lopez <slp@redhat.com> Tested-by: Sergio Lopez <slp@redhat.com> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> Acked-by: Jia He <justin.he@arm.com> Link: https://lore.kernel.org/r/20201120104736.73749-1-sgarzare@redhat.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
Starting from commit 8692cefc433f ("virtio_vsock: Fix race condition
in virtio_transport_recv_pkt"), we discard packets in
virtio_transport_recv_pkt() if the socket has been released.

When the socket is connected, we schedule a delayed work to wait the
RST packet from the other peer, also if SHUTDOWN_MASK is set in
sk->sk_shutdown.
This is done to complete the virtio-vsock shutdown algorithm, releasing
the port assigned to the socket definitively only when the other peer
has consumed all the packets.

If we discard the RST packet received, the socket will be closed only
when the VSOCK_CLOSE_TIMEOUT is reached.

Sergio discovered the issue while running ab(1) HTTP benchmark using
libkrun [1] and observing a latency increase with that commit.

To avoid this issue, we discard packet only if the socket is really
closed (SOCK_DONE flag is set).
We also set SOCK_DONE in virtio_transport_release() when we don't need
to wait any packets from the other peer (we didn't schedule the delayed
work). In this case we remove the socket from the vsock lists, releasing
the port assigned.

[1] https://github.com/containers/libkrun

Fixes: 8692cefc433f ("virtio_vsock: Fix race condition in virtio_transport_recv_pkt")
Cc: justin.he@arm.com
Reported-by: Sergio Lopez <slp@redhat.com>
Tested-by: Sergio Lopez <slp@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Acked-by: Jia He <justin.he@arm.com>
Link: https://lore.kernel.org/r/20201120104736.73749-1-sgarzare@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
vsock: forward all packets to the host when no H2G is registered 2020-11-14T19:33:39+00:00 Stefano Garzarella sgarzare@redhat.com 2020-11-12T13:38:37+00:00 65b422d9b61ba12c08150784e8012fa1892ad03e Before commit c0cfa2d8a788 ("vsock: add multi-transports support"), if a G2H transport was loaded (e.g. virtio transport), every packets was forwarded to the host, regardless of the destination CID. The H2G transports implemented until then (vhost-vsock, VMCI) always responded with an error, if the destination CID was not VMADDR_CID_HOST. From that commit, we are using the remote CID to decide which transport to use, so packets with remote CID > VMADDR_CID_HOST(2) are sent only through H2G transport. If no H2G is available, packets are discarded directly in the guest. Some use cases (e.g. Nitro Enclaves [1]) rely on the old behaviour to implement sibling VMs communication, so we restore the old behavior when no H2G is registered. It will be up to the host to discard packets if the destination is not the right one. As it was already implemented before adding multi-transport support. Tested with nested QEMU/KVM by me and Nitro Enclaves by Andra. [1] Documentation/virt/ne_overview.rst Cc: Jorgen Hansen <jhansen@vmware.com> Cc: Dexuan Cui <decui@microsoft.com> Fixes: c0cfa2d8a788 ("vsock: add multi-transports support") Reported-by: Andra Paraschiv <andraprs@amazon.com> Tested-by: Andra Paraschiv <andraprs@amazon.com> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> Link: https://lore.kernel.org/r/20201112133837.34183-1-sgarzare@redhat.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
Before commit c0cfa2d8a788 ("vsock: add multi-transports support"),
if a G2H transport was loaded (e.g. virtio transport), every packets
was forwarded to the host, regardless of the destination CID.
The H2G transports implemented until then (vhost-vsock, VMCI) always
responded with an error, if the destination CID was not
VMADDR_CID_HOST.

From that commit, we are using the remote CID to decide which
transport to use, so packets with remote CID > VMADDR_CID_HOST(2)
are sent only through H2G transport. If no H2G is available, packets
are discarded directly in the guest.

Some use cases (e.g. Nitro Enclaves [1]) rely on the old behaviour
to implement sibling VMs communication, so we restore the old
behavior when no H2G is registered.
It will be up to the host to discard packets if the destination is
not the right one. As it was already implemented before adding
multi-transport support.

Tested with nested QEMU/KVM by me and Nitro Enclaves by Andra.

[1] Documentation/virt/ne_overview.rst

Cc: Jorgen Hansen <jhansen@vmware.com>
Cc: Dexuan Cui <decui@microsoft.com>
Fixes: c0cfa2d8a788 ("vsock: add multi-transports support")
Reported-by: Andra Paraschiv <andraprs@amazon.com>
Tested-by: Andra Paraschiv <andraprs@amazon.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Link: https://lore.kernel.org/r/20201112133837.34183-1-sgarzare@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
vsock: use ns_capable_noaudit() on socket create 2020-10-26T23:22:42+00:00 Jeff Vander Stoep jeffv@google.com 2020-10-23T14:37:57+00:00 af545bb5ee53f5261db631db2ac4cde54038bdaf During __vsock_create() CAP_NET_ADMIN is used to determine if the vsock_sock->trusted should be set to true. This value is used later for determing if a remote connection should be allowed to connect to a restricted VM. Unfortunately, if the caller doesn't have CAP_NET_ADMIN, an audit message such as an selinux denial is generated even if the caller does not want a trusted socket. Logging errors on success is confusing. To avoid this, switch the capable(CAP_NET_ADMIN) check to the noaudit version. Reported-by: Roman Kiryanov <rkir@google.com> https://android-review.googlesource.com/c/device/generic/goldfish/+/1468545/ Signed-off-by: Jeff Vander Stoep <jeffv@google.com> Reviewed-by: James Morris <jamorris@linux.microsoft.com> Link: https://lore.kernel.org/r/20201023143757.377574-1-jeffv@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
During __vsock_create() CAP_NET_ADMIN is used to determine if the
vsock_sock->trusted should be set to true. This value is used later
for determing if a remote connection should be allowed to connect
to a restricted VM. Unfortunately, if the caller doesn't have
CAP_NET_ADMIN, an audit message such as an selinux denial is
generated even if the caller does not want a trusted socket.

Logging errors on success is confusing. To avoid this, switch the
capable(CAP_NET_ADMIN) check to the noaudit version.

Reported-by: Roman Kiryanov <rkir@google.com>
https://android-review.googlesource.com/c/device/generic/goldfish/+/1468545/
Signed-off-by: Jeff Vander Stoep <jeffv@google.com>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Link: https://lore.kernel.org/r/20201023143757.377574-1-jeffv@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
vsock: fix potential null pointer dereference in vsock_poll() 2020-08-12T19:56:06+00:00 Stefano Garzarella sgarzare@redhat.com 2020-08-12T12:56:02+00:00 1980c05844830a44708c98c96d600833aa3fae08 syzbot reported this issue where in the vsock_poll() we find the socket state at TCP_ESTABLISHED, but 'transport' is null: general protection fault, probably for non-canonical address 0xdffffc0000000012: 0000 [#1] PREEMPT SMP KASAN KASAN: null-ptr-deref in range [0x0000000000000090-0x0000000000000097] CPU: 0 PID: 8227 Comm: syz-executor.2 Not tainted 5.8.0-rc7-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:vsock_poll+0x75a/0x8e0 net/vmw_vsock/af_vsock.c:1038 Call Trace: sock_poll+0x159/0x460 net/socket.c:1266 vfs_poll include/linux/poll.h:90 [inline] do_pollfd fs/select.c:869 [inline] do_poll fs/select.c:917 [inline] do_sys_poll+0x607/0xd40 fs/select.c:1011 __do_sys_poll fs/select.c:1069 [inline] __se_sys_poll fs/select.c:1057 [inline] __x64_sys_poll+0x18c/0x440 fs/select.c:1057 do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384 entry_SYSCALL_64_after_hwframe+0x44/0xa9 This issue can happen if the TCP_ESTABLISHED state is set after we read the vsk->transport in the vsock_poll(). We could put barriers to synchronize, but this can only happen during connection setup, so we can simply check that 'transport' is valid. Fixes: c0cfa2d8a788 ("vsock: add multi-transports support") Reported-and-tested-by: syzbot+a61bac2fcc1a7c6623fe@syzkaller.appspotmail.com Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> Reviewed-by: Jorgen Hansen <jhansen@vmware.com> Signed-off-by: David S. Miller <davem@davemloft.net> 
syzbot reported this issue where in the vsock_poll() we find the
socket state at TCP_ESTABLISHED, but 'transport' is null:
  general protection fault, probably for non-canonical address 0xdffffc0000000012: 0000 [#1] PREEMPT SMP KASAN
  KASAN: null-ptr-deref in range [0x0000000000000090-0x0000000000000097]
  CPU: 0 PID: 8227 Comm: syz-executor.2 Not tainted 5.8.0-rc7-syzkaller #0
  Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
  RIP: 0010:vsock_poll+0x75a/0x8e0 net/vmw_vsock/af_vsock.c:1038
  Call Trace:
   sock_poll+0x159/0x460 net/socket.c:1266
   vfs_poll include/linux/poll.h:90 [inline]
   do_pollfd fs/select.c:869 [inline]
   do_poll fs/select.c:917 [inline]
   do_sys_poll+0x607/0xd40 fs/select.c:1011
   __do_sys_poll fs/select.c:1069 [inline]
   __se_sys_poll fs/select.c:1057 [inline]
   __x64_sys_poll+0x18c/0x440 fs/select.c:1057
   do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384
   entry_SYSCALL_64_after_hwframe+0x44/0xa9

This issue can happen if the TCP_ESTABLISHED state is set after we read
the vsk->transport in the vsock_poll().

We could put barriers to synchronize, but this can only happen during
connection setup, so we can simply check that 'transport' is valid.

Fixes: c0cfa2d8a788 ("vsock: add multi-transports support")
Reported-and-tested-by: syzbot+a61bac2fcc1a7c6623fe@syzkaller.appspotmail.com
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Jorgen Hansen <jhansen@vmware.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-07-26T00:49:04+00:00 David S. Miller davem@davemloft.net 2020-07-26T00:49:04+00:00 a57066b1a01977a646145f4ce8dfb4538b08368a The UDP reuseport conflict was a little bit tricky. The net-next code, via bpf-next, extracted the reuseport handling into a helper so that the BPF sk lookup code could invoke it. At the same time, the logic for reuseport handling of unconnected sockets changed via commit efc6b6f6c3113e8b203b9debfb72d81e0f3dcace which changed the logic to carry on the reuseport result into the rest of the lookup loop if we do not return immediately. This requires moving the reuseport_has_conns() logic into the callers. While we are here, get rid of inline directives as they do not belong in foo.c files. The other changes were cases of more straightforward overlapping modifications. Signed-off-by: David S. Miller <davem@davemloft.net> 
The UDP reuseport conflict was a little bit tricky.

The net-next code, via bpf-next, extracted the reuseport handling
into a helper so that the BPF sk lookup code could invoke it.

At the same time, the logic for reuseport handling of unconnected
sockets changed via commit efc6b6f6c3113e8b203b9debfb72d81e0f3dcace
which changed the logic to carry on the reuseport result into the
rest of the lookup loop if we do not return immediately.

This requires moving the reuseport_has_conns() logic into the callers.

While we are here, get rid of inline directives as they do not belong
in foo.c files.

The other changes were cases of more straightforward overlapping
modifications.

Signed-off-by: David S. Miller <davem@davemloft.net>
net: pass a sockptr_t into ->setsockopt 2020-07-24T22:41:54+00:00 Christoph Hellwig hch@lst.de 2020-07-23T06:09:07+00:00 a7b75c5a8c41445f33efb663887ff5f5c3b4454b Rework the remaining setsockopt code to pass a sockptr_t instead of a plain user pointer. This removes the last remaining set_fs(KERNEL_DS) outside of architecture specific code. Signed-off-by: Christoph Hellwig <hch@lst.de> Acked-by: Stefan Schmidt <stefan@datenfreihafen.org> [ieee802154] Acked-by: Matthieu Baerts <matthieu.baerts@tessares.net> Signed-off-by: David S. Miller <davem@davemloft.net> 
Rework the remaining setsockopt code to pass a sockptr_t instead of a
plain user pointer.  This removes the last remaining set_fs(KERNEL_DS)
outside of architecture specific code.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Stefan Schmidt <stefan@datenfreihafen.org> [ieee802154]
Acked-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
net: make ->{get,set}sockopt in proto_ops optional 2020-07-20T01:16:41+00:00 Christoph Hellwig hch@lst.de 2020-07-17T06:23:31+00:00 a44d9e72100f7044ac46e4e6dc475f5b4097830f Just check for a NULL method instead of wiring up sock_no_{get,set}sockopt. Signed-off-by: Christoph Hellwig <hch@lst.de> Acked-by: Marc Kleine-Budde <mkl@pengutronix.de> Signed-off-by: David S. Miller <davem@davemloft.net> 
Just check for a NULL method instead of wiring up
sock_no_{get,set}sockopt.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
vsock/virtio: annotate 'the_virtio_vsock' RCU pointer 2020-07-16T00:47:15+00:00 Stefano Garzarella sgarzare@redhat.com 2020-07-10T12:12:43+00:00 f961134a612c793d5901a93d85a29337c74af978 Commit 0deab087b16a ("vsock/virtio: use RCU to avoid use-after-free on the_virtio_vsock") starts to use RCU to protect 'the_virtio_vsock' pointer, but we forgot to annotate it. This patch adds the annotation to fix the following sparse errors: net/vmw_vsock/virtio_transport.c:73:17: error: incompatible types in comparison expression (different address spaces): net/vmw_vsock/virtio_transport.c:73:17: struct virtio_vsock [noderef] __rcu * net/vmw_vsock/virtio_transport.c:73:17: struct virtio_vsock * net/vmw_vsock/virtio_transport.c:171:17: error: incompatible types in comparison expression (different address spaces): net/vmw_vsock/virtio_transport.c:171:17: struct virtio_vsock [noderef] __rcu * net/vmw_vsock/virtio_transport.c:171:17: struct virtio_vsock * net/vmw_vsock/virtio_transport.c:207:17: error: incompatible types in comparison expression (different address spaces): net/vmw_vsock/virtio_transport.c:207:17: struct virtio_vsock [noderef] __rcu * net/vmw_vsock/virtio_transport.c:207:17: struct virtio_vsock * net/vmw_vsock/virtio_transport.c:561:13: error: incompatible types in comparison expression (different address spaces): net/vmw_vsock/virtio_transport.c:561:13: struct virtio_vsock [noderef] __rcu * net/vmw_vsock/virtio_transport.c:561:13: struct virtio_vsock * net/vmw_vsock/virtio_transport.c:612:9: error: incompatible types in comparison expression (different address spaces): net/vmw_vsock/virtio_transport.c:612:9: struct virtio_vsock [noderef] __rcu * net/vmw_vsock/virtio_transport.c:612:9: struct virtio_vsock * net/vmw_vsock/virtio_transport.c:631:9: error: incompatible types in comparison expression (different address spaces): net/vmw_vsock/virtio_transport.c:631:9: struct virtio_vsock [noderef] __rcu * net/vmw_vsock/virtio_transport.c:631:9: struct virtio_vsock * Fixes: 0deab087b16a ("vsock/virtio: use RCU to avoid use-after-free on the_virtio_vsock") Reported-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
Commit 0deab087b16a ("vsock/virtio: use RCU to avoid use-after-free
on the_virtio_vsock") starts to use RCU to protect 'the_virtio_vsock'
pointer, but we forgot to annotate it.

This patch adds the annotation to fix the following sparse errors:

    net/vmw_vsock/virtio_transport.c:73:17: error: incompatible types in comparison expression (different address spaces):
    net/vmw_vsock/virtio_transport.c:73:17:    struct virtio_vsock [noderef] __rcu *
    net/vmw_vsock/virtio_transport.c:73:17:    struct virtio_vsock *
    net/vmw_vsock/virtio_transport.c:171:17: error: incompatible types in comparison expression (different address spaces):
    net/vmw_vsock/virtio_transport.c:171:17:    struct virtio_vsock [noderef] __rcu *
    net/vmw_vsock/virtio_transport.c:171:17:    struct virtio_vsock *
    net/vmw_vsock/virtio_transport.c:207:17: error: incompatible types in comparison expression (different address spaces):
    net/vmw_vsock/virtio_transport.c:207:17:    struct virtio_vsock [noderef] __rcu *
    net/vmw_vsock/virtio_transport.c:207:17:    struct virtio_vsock *
    net/vmw_vsock/virtio_transport.c:561:13: error: incompatible types in comparison expression (different address spaces):
    net/vmw_vsock/virtio_transport.c:561:13:    struct virtio_vsock [noderef] __rcu *
    net/vmw_vsock/virtio_transport.c:561:13:    struct virtio_vsock *
    net/vmw_vsock/virtio_transport.c:612:9: error: incompatible types in comparison expression (different address spaces):
    net/vmw_vsock/virtio_transport.c:612:9:    struct virtio_vsock [noderef] __rcu *
    net/vmw_vsock/virtio_transport.c:612:9:    struct virtio_vsock *
    net/vmw_vsock/virtio_transport.c:631:9: error: incompatible types in comparison expression (different address spaces):
    net/vmw_vsock/virtio_transport.c:631:9:    struct virtio_vsock [noderef] __rcu *
    net/vmw_vsock/virtio_transport.c:631:9:    struct virtio_vsock *

Fixes: 0deab087b16a ("vsock/virtio: use RCU to avoid use-after-free on the_virtio_vsock")
Reported-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
vsock/vmci: make vmci_vsock_transport_cb() static 2020-06-05T20:18:26+00:00 Stefano Garzarella sgarzare@redhat.com 2020-06-05T15:12:41+00:00 fdb4276aae1100aa13f955eff6c944a8200a15ac Fix the following gcc-9.3 warning when building with 'make W=1': net/vmw_vsock/vmci_transport.c:2058:6: warning: no previous prototype for ‘vmci_vsock_transport_cb’ [-Wmissing-prototypes] 2058 | void vmci_vsock_transport_cb(bool is_host) | ^~~~~~~~~~~~~~~~~~~~~~~ Fixes: b1bba80a4376 ("vsock/vmci: register vmci_transport only when VMCI guest/host are active") Reported-by: kernel test robot <lkp@intel.com> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net> 
Fix the following gcc-9.3 warning when building with 'make W=1':
    net/vmw_vsock/vmci_transport.c:2058:6: warning: no previous prototype
        for ‘vmci_vsock_transport_cb’ [-Wmissing-prototypes]
     2058 | void vmci_vsock_transport_cb(bool is_host)
          |      ^~~~~~~~~~~~~~~~~~~~~~~

Fixes: b1bba80a4376 ("vsock/vmci: register vmci_transport only when VMCI guest/host are active")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
virtio_vsock: Fix race condition in virtio_transport_recv_pkt 2020-05-31T00:44:01+00:00 Jia He justin.he@arm.com 2020-05-30T01:38:28+00:00 8692cefc433f282228fd44938dd4d26ed38254a2 When client on the host tries to connect(SOCK_STREAM, O_NONBLOCK) to the server on the guest, there will be a panic on a ThunderX2 (armv8a server): [ 463.718844] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 [ 463.718848] Mem abort info: [ 463.718849] ESR = 0x96000044 [ 463.718852] EC = 0x25: DABT (current EL), IL = 32 bits [ 463.718853] SET = 0, FnV = 0 [ 463.718854] EA = 0, S1PTW = 0 [ 463.718855] Data abort info: [ 463.718856] ISV = 0, ISS = 0x00000044 [ 463.718857] CM = 0, WnR = 1 [ 463.718859] user pgtable: 4k pages, 48-bit VAs, pgdp=0000008f6f6e9000 [ 463.718861] [0000000000000000] pgd=0000000000000000 [ 463.718866] Internal error: Oops: 96000044 [#1] SMP [...] [ 463.718977] CPU: 213 PID: 5040 Comm: vhost-5032 Tainted: G O 5.7.0-rc7+ #139 [ 463.718980] Hardware name: GIGABYTE R281-T91-00/MT91-FS1-00, BIOS F06 09/25/2018 [ 463.718982] pstate: 60400009 (nZCv daif +PAN -UAO) [ 463.718995] pc : virtio_transport_recv_pkt+0x4c8/0xd40 [vmw_vsock_virtio_transport_common] [ 463.718999] lr : virtio_transport_recv_pkt+0x1fc/0xd40 [vmw_vsock_virtio_transport_common] [ 463.719000] sp : ffff80002dbe3c40 [...] [ 463.719025] Call trace: [ 463.719030] virtio_transport_recv_pkt+0x4c8/0xd40 [vmw_vsock_virtio_transport_common] [ 463.719034] vhost_vsock_handle_tx_kick+0x360/0x408 [vhost_vsock] [ 463.719041] vhost_worker+0x100/0x1a0 [vhost] [ 463.719048] kthread+0x128/0x130 [ 463.719052] ret_from_fork+0x10/0x18 The race condition is as follows: Task1 Task2 ===== ===== __sock_release virtio_transport_recv_pkt __vsock_release vsock_find_bound_socket (found sk) lock_sock_nested vsock_remove_sock sock_orphan sk_set_socket(sk, NULL) sk->sk_shutdown = SHUTDOWN_MASK ... release_sock lock_sock virtio_transport_recv_connecting sk->sk_socket->state (panic!) The root cause is that vsock_find_bound_socket can't hold the lock_sock, so there is a small race window between vsock_find_bound_socket() and lock_sock(). If __vsock_release() is running in another task, sk->sk_socket will be set to NULL inadvertently. This fixes it by checking sk->sk_shutdown(suggested by Stefano) after lock_sock since sk->sk_shutdown is set to SHUTDOWN_MASK under the protection of lock_sock_nested. Signed-off-by: Jia He <justin.he@arm.com> Reviewed-by: Stefano Garzarella <sgarzare@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net> 
When client on the host tries to connect(SOCK_STREAM, O_NONBLOCK) to the
server on the guest, there will be a panic on a ThunderX2 (armv8a server):

[  463.718844] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
[  463.718848] Mem abort info:
[  463.718849]   ESR = 0x96000044
[  463.718852]   EC = 0x25: DABT (current EL), IL = 32 bits
[  463.718853]   SET = 0, FnV = 0
[  463.718854]   EA = 0, S1PTW = 0
[  463.718855] Data abort info:
[  463.718856]   ISV = 0, ISS = 0x00000044
[  463.718857]   CM = 0, WnR = 1
[  463.718859] user pgtable: 4k pages, 48-bit VAs, pgdp=0000008f6f6e9000
[  463.718861] [0000000000000000] pgd=0000000000000000
[  463.718866] Internal error: Oops: 96000044 [#1] SMP
[...]
[  463.718977] CPU: 213 PID: 5040 Comm: vhost-5032 Tainted: G           O      5.7.0-rc7+ #139
[  463.718980] Hardware name: GIGABYTE R281-T91-00/MT91-FS1-00, BIOS F06 09/25/2018
[  463.718982] pstate: 60400009 (nZCv daif +PAN -UAO)
[  463.718995] pc : virtio_transport_recv_pkt+0x4c8/0xd40 [vmw_vsock_virtio_transport_common]
[  463.718999] lr : virtio_transport_recv_pkt+0x1fc/0xd40 [vmw_vsock_virtio_transport_common]
[  463.719000] sp : ffff80002dbe3c40
[...]
[  463.719025] Call trace:
[  463.719030]  virtio_transport_recv_pkt+0x4c8/0xd40 [vmw_vsock_virtio_transport_common]
[  463.719034]  vhost_vsock_handle_tx_kick+0x360/0x408 [vhost_vsock]
[  463.719041]  vhost_worker+0x100/0x1a0 [vhost]
[  463.719048]  kthread+0x128/0x130
[  463.719052]  ret_from_fork+0x10/0x18

The race condition is as follows:
Task1                                Task2
=====                                =====
__sock_release                       virtio_transport_recv_pkt
  __vsock_release                      vsock_find_bound_socket (found sk)
    lock_sock_nested
    vsock_remove_sock
    sock_orphan
      sk_set_socket(sk, NULL)
    sk->sk_shutdown = SHUTDOWN_MASK
    ...
    release_sock
                                    lock_sock
                                       virtio_transport_recv_connecting
                                         sk->sk_socket->state (panic!)

The root cause is that vsock_find_bound_socket can't hold the lock_sock,
so there is a small race window between vsock_find_bound_socket() and
lock_sock(). If __vsock_release() is running in another task,
sk->sk_socket will be set to NULL inadvertently.

This fixes it by checking sk->sk_shutdown(suggested by Stefano) after
lock_sock since sk->sk_shutdown is set to SHUTDOWN_MASK under the
protection of lock_sock_nested.

Signed-off-by: Jia He <justin.he@arm.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>