kernel/linux.git/net/vmw_vsock, branch v6.18.21

vmw_vsock: bypass false-positive Wnonnull warning with gcc-16

2026-03-04T12:20:25+00:00

[ Upstream commit e25dbf561e03c0c5e36228e3b8b784392819ce85 ] The gcc-16.0.1 snapshot produces a false-positive warning that turns into a build failure with CONFIG_WERROR: In file included from arch/x86/include/asm/string.h:6, from net/vmw_vsock/vmci_transport.c:10: In function 'vmci_transport_packet_init', inlined from '__vmci_transport_send_control_pkt.constprop' at net/vmw_vsock/vmci_transport.c:198:2: arch/x86/include/asm/string_32.h:150:25: error: argument 2 null where non-null expected because argument 3 is nonzero [-Werror=nonnull] 150 | #define memcpy(t, f, n) __builtin_memcpy(t, f, n) | ^~~~~~~~~~~~~~~~~~~~~~~~~ net/vmw_vsock/vmci_transport.c:164:17: note: in expansion of macro 'memcpy' 164 | memcpy(&pkt->u.wait, wait, sizeof(pkt->u.wait)); | ^~~~~~ arch/x86/include/asm/string_32.h:150:25: note: in a call to built-in function '__builtin_memcpy' net/vmw_vsock/vmci_transport.c:164:17: note: in expansion of macro 'memcpy' 164 | memcpy(&pkt->u.wait, wait, sizeof(pkt->u.wait)); | ^~~~~~ This seems relatively harmless, and it so far the only instance of this warning I have found. The __vmci_transport_send_control_pkt function is called either with wait=NULL or with one of the type values that pass 'wait' into memcpy() here, but not from the same caller. Replacing the memcpy with a struct assignment is otherwise the same but avoids the warning. Signed-off-by: Arnd Bergmann Reviewed-by: Bobby Eshleman Reviewed-by: Stefano Garzarella Reviewed-by: Bryan Tan Link: https://patch.msgid.link/20260203163406.2636463-1-arnd@kernel.org Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

vsock/virtio: cap TX credit to local buffer size

2026-01-30T09:32:21+00:00

[ Upstream commit 8ee784fdf006cbe8739cfa093f54d326cbf54037 ] The virtio transports derives its TX credit directly from peer_buf_alloc, which is set from the remote endpoint's SO_VM_SOCKETS_BUFFER_SIZE value. On the host side this means that the amount of data we are willing to queue for a connection is scaled by a guest-chosen buffer size, rather than the host's own vsock configuration. A malicious guest can advertise a large buffer and read slowly, causing the host to allocate a correspondingly large amount of sk_buff memory. The same thing would happen in the guest with a malicious host, since virtio transports share the same code base. Introduce a small helper, virtio_transport_tx_buf_size(), that returns min(peer_buf_alloc, buf_alloc), and use it wherever we consume peer_buf_alloc. This ensures the effective TX window is bounded by both the peer's advertised buffer and our own buf_alloc (already clamped to buffer_max_size via SO_VM_SOCKETS_BUFFER_MAX_SIZE), so a remote peer cannot force the other to queue more data than allowed by its own vsock settings. On an unpatched Ubuntu 22.04 host (~64 GiB RAM), running a PoC with 32 guest vsock connections advertising 2 GiB each and reading slowly drove Slab/SUnreclaim from ~0.5 GiB to ~57 GiB; the system only recovered after killing the QEMU process. That said, if QEMU memory is limited with cgroups, the maximum memory used will be limited. With this patch applied: Before: MemFree: ~61.6 GiB Slab: ~142 MiB SUnreclaim: ~117 MiB After 32 high-credit connections: MemFree: ~61.5 GiB Slab: ~178 MiB SUnreclaim: ~152 MiB Only ~35 MiB increase in Slab/SUnreclaim, no host OOM, and the guest remains responsive. Compatibility with non-virtio transports: - VMCI uses the AF_VSOCK buffer knobs to size its queue pairs per socket based on the local vsk->buffer_* values; the remote side cannot enlarge those queues beyond what the local endpoint configured. - Hyper-V's vsock transport uses fixed-size VMBus ring buffers and an MTU bound; there is no peer-controlled credit field comparable to peer_buf_alloc, and the remote endpoint cannot drive in-flight kernel memory above those ring sizes. - The loopback path reuses virtio_transport_common.c, so it naturally follows the same semantics as the virtio transport. This change is limited to virtio_transport_common.c and thus affects virtio-vsock, vhost-vsock, and loopback, bringing them in line with the "remote window intersected with local policy" behaviour that VMCI and Hyper-V already effectively have. Fixes: 06a8fc78367d ("VSOCK: Introduce virtio_vsock_common.ko") Suggested-by: Stefano Garzarella Signed-off-by: Melbin K Mathew [Stefano: small adjustments after changing the previous patch] [Stefano: tweak the commit message] Signed-off-by: Stefano Garzarella Reviewed-by: Luigi Leonardi Link: https://patch.msgid.link/20260121093628.9941-4-sgarzare@redhat.com Acked-by: Michael S. Tsirkin Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin

vsock/virtio: fix potential underflow in virtio_transport_get_credit()

2026-01-30T09:32:21+00:00

[ Upstream commit 3ef3d52a1a9860d094395c7a3e593f3aa26ff012 ] The credit calculation in virtio_transport_get_credit() uses unsigned arithmetic: ret = vvs->peer_buf_alloc - (vvs->tx_cnt - vvs->peer_fwd_cnt); If the peer shrinks its advertised buffer (peer_buf_alloc) while bytes are in flight, the subtraction can underflow and produce a large positive value, potentially allowing more data to be queued than the peer can handle. Reuse virtio_transport_has_space() which already handles this case and add a comment to make it clear why we are doing that. Fixes: 06a8fc78367d ("VSOCK: Introduce virtio_vsock_common.ko") Suggested-by: Stefano Garzarella Signed-off-by: Melbin K Mathew [Stefano: use virtio_transport_has_space() instead of duplicating the code] [Stefano: tweak the commit message] Signed-off-by: Stefano Garzarella Reviewed-by: Luigi Leonardi Link: https://patch.msgid.link/20260121093628.9941-2-sgarzare@redhat.com Acked-by: Michael S. Tsirkin Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin

vsock/virtio: Coalesce only linear skb

2026-01-30T09:32:11+00:00

[ Upstream commit 0386bd321d0f95d041a7b3d7b07643411b044a96 ] vsock/virtio common tries to coalesce buffers in rx queue: if a linear skb (with a spare tail room) is followed by a small skb (length limited by GOOD_COPY_LEN = 128), an attempt is made to join them. Since the introduction of MSG_ZEROCOPY support, assumption that a small skb will always be linear is incorrect. In the zerocopy case, data is lost and the linear skb is appended with uninitialized kernel memory. Of all 3 supported virtio-based transports, only loopback-transport is affected. G2H virtio-transport rx queue operates on explicitly linear skbs; see virtio_vsock_alloc_linear_skb() in virtio_vsock_rx_fill(). H2G vhost-transport may allocate non-linear skbs, but only for sizes that are not considered for coalescence; see PAGE_ALLOC_COSTLY_ORDER in virtio_vsock_alloc_skb(). Ensure only linear skbs are coalesced. Note that skb_tailroom(last_skb) > 0 guarantees last_skb is linear. Fixes: 581512a6dc93 ("vsock/virtio: MSG_ZEROCOPY flag support") Signed-off-by: Michal Luczaj Reviewed-by: Stefano Garzarella Link: https://patch.msgid.link/20260113-vsock-recv-coalescence-v2-1-552b17837cf4@rbox.co Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

vsock: Make accept()ed sockets use custom setsockopt()

2026-01-17T15:35:25+00:00

[ Upstream commit ce5e612dd411de096aa041b9e9325ba1bec5f9f4 ] SO_ZEROCOPY handling in vsock_connectible_setsockopt() does not get called on accept()ed sockets due to a missing flag. Flip it. Fixes: e0718bd82e27 ("vsock: enable setting SO_ZEROCOPY") Signed-off-by: Michal Luczaj Link: https://patch.msgid.link/20251229-vsock-child-sock-custom-sockopt-v2-1-64778d6c4f88@rbox.co Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

vsock: Ignore signal/timeout on connect() if already established

2025-11-20T15:40:06+00:00

During connect(), acting on a signal/timeout by disconnecting an already established socket leads to several issues: 1. connect() invoking vsock_transport_cancel_pkt() -> virtio_transport_purge_skbs() may race with sendmsg() invoking virtio_transport_get_credit(). This results in a permanently elevated `vvs->bytes_unsent`. Which, in turn, confuses the SOCK_LINGER handling. 2. connect() resetting a connected socket's state may race with socket being placed in a sockmap. A disconnected socket remaining in a sockmap breaks sockmap's assumptions. And gives rise to WARNs. 3. connect() transitioning SS_CONNECTED -> SS_UNCONNECTED allows for a transport change/drop after TCP_ESTABLISHED. Which poses a problem for any simultaneous sendmsg() or connect() and may result in a use-after-free/null-ptr-deref. Do not disconnect socket on signal/timeout. Keep the logic for unconnected sockets: they don't linger, can't be placed in a sockmap, are rejected by sendmsg(). [1]: https://lore.kernel.org/netdev/e07fd95c-9a38-4eea-9638-133e38c2ec9b@rbox.co/ [2]: https://lore.kernel.org/netdev/20250317-vsock-trans-signal-race-v4-0-fc8837f3f1d4@rbox.co/ [3]: https://lore.kernel.org/netdev/60f1b7db-3099-4f6a-875e-af9f6ef194f6@rbox.co/ Fixes: d021c344051a ("VSOCK: Introduce VM Sockets") Signed-off-by: Michal Luczaj Reviewed-by: Stefano Garzarella Link: https://patch.msgid.link/20251119-vsock-interrupted-connect-v2-1-70734cf1233f@rbox.co Signed-off-by: Jakub Kicinski

vsock: fix lock inversion in vsock_assign_transport()

2025-10-23T14:07:58+00:00

Syzbot reported a potential lock inversion deadlock between vsock_register_mutex and sk_lock-AF_VSOCK when vsock_linger() is called. The issue was introduced by commit 687aa0c5581b ("vsock: Fix transport_* TOCTOU") which added vsock_register_mutex locking in vsock_assign_transport() around the transport->release() call, that can call vsock_linger(). vsock_assign_transport() can be called with sk_lock held. vsock_linger() calls sk_wait_event() that temporarily releases and re-acquires sk_lock. During this window, if another thread hold vsock_register_mutex while trying to acquire sk_lock, a circular dependency is created. Fix this by releasing vsock_register_mutex before calling transport->release() and vsock_deassign_transport(). This is safe because we don't need to hold vsock_register_mutex while releasing the old transport, and we ensure the new transport won't disappear by obtaining a module reference first via try_module_get(). Reported-by: syzbot+10e35716f8e4929681fa@syzkaller.appspotmail.com Tested-by: syzbot+10e35716f8e4929681fa@syzkaller.appspotmail.com Fixes: 687aa0c5581b ("vsock: Fix transport_* TOCTOU") Cc: mhal@rbox.co Cc: stable@vger.kernel.org Signed-off-by: Stefano Garzarella Link: https://patch.msgid.link/20251021121718.137668-1-sgarzare@redhat.com Signed-off-by: Paolo Abeni

Merge tag 'hyperv-next-signed-20251006' of git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux

2025-10-07T15:40:15+00:00

Pull hyperv updates from Wei Liu: - Unify guest entry code for KVM and MSHV (Sean Christopherson) - Switch Hyper-V MSI domain to use msi_create_parent_irq_domain() (Nam Cao) - Add CONFIG_HYPERV_VMBUS and limit the semantics of CONFIG_HYPERV (Mukesh Rathor) - Add kexec/kdump support on Azure CVMs (Vitaly Kuznetsov) - Deprecate hyperv_fb in favor of Hyper-V DRM driver (Prasanna Kumar T S M) - Miscellaneous enhancements, fixes and cleanups (Abhishek Tiwari, Alok Tiwari, Nuno Das Neves, Wei Liu, Roman Kisel, Michael Kelley) * tag 'hyperv-next-signed-20251006' of git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux: hyperv: Remove the spurious null directive line MAINTAINERS: Mark hyperv_fb driver Obsolete fbdev/hyperv_fb: deprecate this in favor of Hyper-V DRM driver Drivers: hv: Make CONFIG_HYPERV bool Drivers: hv: Add CONFIG_HYPERV_VMBUS option Drivers: hv: vmbus: Fix typos in vmbus_drv.c Drivers: hv: vmbus: Fix sysfs output format for ring buffer index Drivers: hv: vmbus: Clean up sscanf format specifier in target_cpu_store() x86/hyperv: Switch to msi_create_parent_irq_domain() mshv: Use common "entry virt" APIs to do work in root before running guest entry: Rename "kvm" entry code assets to "virt" to genericize APIs entry/kvm: KVM: Move KVM details related to signal/-EINTR into KVM proper mshv: Handle NEED_RESCHED_LAZY before transferring to guest x86/hyperv: Add kexec/kdump support on Azure CVMs Drivers: hv: Simplify data structures for VMBus channel close message Drivers: hv: util: Cosmetic changes for hv_utils_transport.c mshv: Add support for a new parent partition configuration clocksource: hyper-v: Skip unnecessary checks for the root partition hyperv: Add missing field to hv_output_map_device_interrupt

Drivers: hv: Add CONFIG_HYPERV_VMBUS option

2025-10-01T00:00:42+00:00

At present VMBus driver is hinged off of CONFIG_HYPERV which entails lot of builtin code and encompasses too much. It's not always clear what depends on builtin hv code and what depends on VMBus. Setting CONFIG_HYPERV as a module and fudging the Makefile to switch to builtin adds even more confusion. VMBus is an independent module and should have its own config option. Also, there are scenarios like baremetal dom0/root where support is built in with CONFIG_HYPERV but without VMBus. Lastly, there are more features coming down that use CONFIG_HYPERV and add more dependencies on it. So, create a fine grained HYPERV_VMBUS option and update Kconfigs for dependency on VMBus. Signed-off-by: Mukesh Rathor Acked-by: Bjorn Helgaas # drivers/pci Signed-off-by: Wei Liu

net: WQ_PERCPU added to alloc_workqueue users

2025-09-23T00:40:30+00:00

Currently if a user enqueue a work item using schedule_delayed_work() the used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to schedule_work() that is using system_wq and queue_work(), that makes use again of WORK_CPU_UNBOUND. This lack of consistentcy cannot be addressed without refactoring the API. alloc_workqueue() treats all queues as per-CPU by default, while unbound workqueues must opt-in via WQ_UNBOUND. This default is suboptimal: most workloads benefit from unbound queues, allowing the scheduler to place worker threads where they’re needed and reducing noise when CPUs are isolated. This change adds a new WQ_PERCPU flag at the network subsystem, to explicitly request the use of the per-CPU behavior. Both flags coexist for one release cycle to allow callers to transition their calls. Once migration is complete, WQ_UNBOUND can be removed and unbound will become the implicit default. With the introduction of the WQ_PERCPU flag (equivalent to !WQ_UNBOUND), any alloc_workqueue() caller that doesn’t explicitly specify WQ_UNBOUND must now use WQ_PERCPU. All existing users have been updated accordingly. Suggested-by: Tejun Heo Signed-off-by: Marco Crivellari Link: https://patch.msgid.link/20250918142427.309519-4-marco.crivellari@suse.com Signed-off-by: Jakub Kicinski