kernel/linux.git/drivers/vhost/vsock.c, branch v5.15.208

vhost/vsock: improve RCU read sections around vhost_vsock_get()

2026-01-19T12:09:48+00:00

[ Upstream commit d8ee3cfdc89b75dc059dc21c27bef2c1440f67eb ] vhost_vsock_get() uses hash_for_each_possible_rcu() to find the `vhost_vsock` associated with the `guest_cid`. hash_for_each_possible_rcu() should only be called within an RCU read section, as mentioned in the following comment in include/linux/rculist.h: /** * hlist_for_each_entry_rcu - iterate over rcu list of given type * @pos: the type * to use as a loop cursor. * @head: the head for your list. * @member: the name of the hlist_node within the struct. * @cond: optional lockdep expression if called from non-RCU protection. * * This list-traversal primitive may safely run concurrently with * the _rcu list-mutation primitives such as hlist_add_head_rcu() * as long as the traversal is guarded by rcu_read_lock(). */ Currently, all calls to vhost_vsock_get() are between rcu_read_lock() and rcu_read_unlock() except for calls in vhost_vsock_set_cid() and vhost_vsock_reset_orphans(). In both cases, the current code is safe, but we can make improvements to make it more robust. About vhost_vsock_set_cid(), when building the kernel with CONFIG_PROVE_RCU_LIST enabled, we get the following RCU warning when the user space issues `ioctl(dev, VHOST_VSOCK_SET_GUEST_CID, ...)` : WARNING: suspicious RCU usage 6.18.0-rc7 #62 Not tainted ----------------------------- drivers/vhost/vsock.c:74 RCU-list traversed in non-reader section!! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 1 lock held by rpc-libvirtd/3443: #0: ffffffffc05032a8 (vhost_vsock_mutex){+.+.}-{4:4}, at: vhost_vsock_dev_ioctl+0x2ff/0x530 [vhost_vsock] stack backtrace: CPU: 2 UID: 0 PID: 3443 Comm: rpc-libvirtd Not tainted 6.18.0-rc7 #62 PREEMPT(none) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-7.fc42 06/10/2025 Call Trace: dump_stack_lvl+0x75/0xb0 dump_stack+0x14/0x1a lockdep_rcu_suspicious.cold+0x4e/0x97 vhost_vsock_get+0x8f/0xa0 [vhost_vsock] vhost_vsock_dev_ioctl+0x307/0x530 [vhost_vsock] __x64_sys_ioctl+0x4f2/0xa00 x64_sys_call+0xed0/0x1da0 do_syscall_64+0x73/0xfa0 entry_SYSCALL_64_after_hwframe+0x76/0x7e ... This is not a real problem, because the vhost_vsock_get() caller, i.e. vhost_vsock_set_cid(), holds the `vhost_vsock_mutex` used by the hash table writers. Anyway, to prevent that warning, add lockdep_is_held() condition to hash_for_each_possible_rcu() to verify that either the caller is in an RCU read section or `vhost_vsock_mutex` is held when CONFIG_PROVE_RCU_LIST is enabled; and also clarify the comment for vhost_vsock_get() to better describe the locking requirements and the scope of the returned pointer validity. About vhost_vsock_reset_orphans(), currently this function is only called via vsock_for_each_connected_socket(), which holds the `vsock_table_lock` spinlock (which is also an RCU read-side critical section). However, add an explicit RCU read lock there to make the code more robust and explicit about the RCU requirements, and to prevent issues if the calling context changes in the future or if vhost_vsock_reset_orphans() is called from other contexts. Fixes: 834e772c8db0 ("vhost/vsock: fix use-after-free in network stack callers") Cc: stefanha@redhat.com Signed-off-by: Stefano Garzarella Reviewed-by: Stefan Hajnoczi Message-Id: <20251126133826.142496-1-sgarzare@redhat.com> Message-ID: <20251126210313.GA499503@fedora> Acked-by: Jason Wang Signed-off-by: Michael S. Tsirkin Signed-off-by: Sasha Levin

vhost/vsock: always initialize seqpacket_allow

2024-08-19T03:45:06+00:00

[ Upstream commit 1e1fdcbdde3b7663e5d8faeb2245b9b151417d22 ] There are two issues around seqpacket_allow: 1. seqpacket_allow is not initialized when socket is created. Thus if features are never set, it will be read uninitialized. 2. if VIRTIO_VSOCK_F_SEQPACKET is set and then cleared, then seqpacket_allow will not be cleared appropriately (existing apps I know about don't usually do this but it's legal and there's no way to be sure no one relies on this). To fix: - initialize seqpacket_allow after allocation - set it unconditionally in set_features Reported-by: syzbot+6c21aeb59d0e82eb2782@syzkaller.appspotmail.com Reported-by: Jeongjun Park Fixes: ced7b713711f ("vhost/vsock: support SEQPACKET for transport"). Tested-by: Arseny Krasnov Cc: David S. Miller Cc: Stefan Hajnoczi Message-ID: <20240422100010-mutt-send-email-mst@kernel.org> Signed-off-by: Michael S. Tsirkin Acked-by: Jason Wang Reviewed-by: Stefano Garzarella Reviewed-by: Eugenio Pérez Acked-by: Jakub Kicinski Signed-off-by: Sasha Levin

vhost/vsock: Fix error handling in vhost_vsock_init()

2023-01-12T10:59:11+00:00

[ Upstream commit 7a4efe182ca61fb3e5307e69b261c57cbf434cd4 ] A problem about modprobe vhost_vsock failed is triggered with the following log given: modprobe: ERROR: could not insert 'vhost_vsock': Device or resource busy The reason is that vhost_vsock_init() returns misc_register() directly without checking its return value, if misc_register() failed, it returns without calling vsock_core_unregister() on vhost_transport, resulting the vhost_vsock can never be installed later. A simple call graph is shown as below: vhost_vsock_init() vsock_core_register() # register vhost_transport misc_register() device_create_with_groups() device_create_groups_vargs() dev = kzalloc(...) # OOM happened # return without unregister vhost_transport Fix by calling vsock_core_unregister() when misc_register() returns error. Fixes: 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko") Signed-off-by: Yuan Can Message-Id: <20221108101705.45981-1-yuancan@huawei.com> Signed-off-by: Michael S. Tsirkin Reviewed-by: Stefano Garzarella Acked-by: Jason Wang Signed-off-by: Sasha Levin

vhost/vsock: Use kvmalloc/kvfree for larger packets.

2022-10-26T10:34:47+00:00

[ Upstream commit 0e3f72931fc47bb81686020cc643cde5d9cd0bb8 ] When copying a large file over sftp over vsock, data size is usually 32kB, and kmalloc seems to fail to try to allocate 32 32kB regions. vhost-5837: page allocation failure: order:4, mode:0x24040c0 Call Trace: [] dump_stack+0x97/0xdb [] warn_alloc_failed+0x10f/0x138 [] ? __alloc_pages_direct_compact+0x38/0xc8 [] __alloc_pages_nodemask+0x84c/0x90d [] alloc_kmem_pages+0x17/0x19 [] kmalloc_order_trace+0x2b/0xdb [] __kmalloc+0x177/0x1f7 [] ? copy_from_iter+0x8d/0x31d [] vhost_vsock_handle_tx_kick+0x1fa/0x301 [vhost_vsock] [] vhost_worker+0xf7/0x157 [vhost] [] kthread+0xfd/0x105 [] ? vhost_dev_set_owner+0x22e/0x22e [vhost] [] ? flush_kthread_worker+0xf3/0xf3 [] ret_from_fork+0x4e/0x80 [] ? flush_kthread_worker+0xf3/0xf3 Work around by doing kvmalloc instead. Fixes: 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko") Signed-off-by: Junichi Uekawa Reviewed-by: Stefano Garzarella Acked-by: Michael S. Tsirkin Link: https://lore.kernel.org/r/20220928064538.667678-1-uekawa@chromium.org Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

vsock: each transport cycles only on its own sockets

2022-03-23T08:16:41+00:00

[ Upstream commit 8e6ed963763fe21429eabfc76c69ce2b0163a3dd ] When iterating over sockets using vsock_for_each_connected_socket, make sure that a transport filters out sockets that don't belong to the transport. There actually was an issue caused by this; in a nested VM configuration, destroying the nested VM (which often involves the closing of /dev/vhost-vsock if there was h2g connections to the nested VM) kills not only the h2g connections, but also all existing g2h connections to the (outmost) host which are totally unrelated. Tested: Executed the following steps on Cuttlefish (Android running on a VM) [1]: (1) Enter into an `adb shell` session - to have a g2h connection inside the VM, (2) open and then close /dev/vhost-vsock by `exec 3< /dev/vhost-vsock && exec 3<&-`, (3) observe that the adb session is not reset. [1] https://android.googlesource.com/device/google/cuttlefish/ Fixes: c0cfa2d8a788 ("vsock: add multi-transports support") Reviewed-by: Stefano Garzarella Acked-by: Michael S. Tsirkin Signed-off-by: Jiyong Park Link: https://lore.kernel.org/r/20220311020017.1509316-1-jiyong@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

vhost/vsock: don't check owner in vhost_vsock_stop() while releasing

2022-03-02T10:47:48+00:00

commit a58da53ffd70294ebea8ecd0eb45fd0d74add9f9 upstream. vhost_vsock_stop() calls vhost_dev_check_owner() to check the device ownership. It expects current->mm to be valid. vhost_vsock_stop() is also called by vhost_vsock_dev_release() when the user has not done close(), so when we are in do_exit(). In this case current->mm is invalid and we're releasing the device, so we should clean it anyway. Let's check the owner only when vhost_vsock_stop() is called by an ioctl. When invoked from release we can not fail so we don't check return code of vhost_vsock_stop(). We need to stop vsock even if it's not the owner. Fixes: 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko") Cc: stable@vger.kernel.org Reported-by: syzbot+1e3ea63db39f2b4440e0@syzkaller.appspotmail.com Reported-and-tested-by: syzbot+3140b17cb44a7b174008@syzkaller.appspotmail.com Signed-off-by: Stefano Garzarella Acked-by: Jason Wang Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman

vhost/vsock: fix incorrect used length reported to the guest

2021-12-01T08:04:55+00:00

commit 49d8c5ffad07ca014cfae72a1b9b8c52b6ad9cb8 upstream. The "used length" reported by calling vhost_add_used() must be the number of bytes written by the device (using "in" buffers). In vhost_vsock_handle_tx_kick() the device only reads the guest buffers (they are all "out" buffers), without writing anything, so we must pass 0 as "used length" to comply virtio spec. Fixes: 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko") Cc: stable@vger.kernel.org Reported-by: Halil Pasic Suggested-by: Jason Wang Signed-off-by: Stefano Garzarella Link: https://lore.kernel.org/r/20211122163525.294024-2-sgarzare@redhat.com Signed-off-by: Michael S. Tsirkin Reviewed-by: Stefan Hajnoczi Reviewed-by: Halil Pasic Signed-off-by: Greg Kroah-Hartman

vhost/vsock: support MSG_EOR bit processing

2021-09-05T20:23:09+00:00

'MSG_EOR' handling has similar logic as 'MSG_EOM' - if bit present in packet's header, reset it to 0. Then restore it back if packet processing wasn't completed. Instead of bool variable for each flag, bit mask variable was added: it has logical OR of 'MSG_EOR' and 'MSG_EOM' if needed, to restore flags, this variable is ORed with flags field of packet. Signed-off-by: Arseny Krasnov Link: https://lore.kernel.org/r/20210903123238.3273526-1-arseny.krasnov@kaspersky.com Signed-off-by: Michael S. Tsirkin Reviewed-by: Stefano Garzarella

virtio/vsock: rename 'EOR' to 'EOM' bit.

2021-09-05T20:23:08+00:00

This current implemented bit is used to mark end of messages ('EOM' - end of message), not records('EOR' - end of record). Also rename 'record' to 'message' in implementation as it is different things. Signed-off-by: Arseny Krasnov Reviewed-by: Stefano Garzarella Link: https://lore.kernel.org/r/20210903123109.3273053-1-arseny.krasnov@kaspersky.com Signed-off-by: Michael S. Tsirkin

vhost: remove work arg from vhost_work_flush

2021-07-03T08:50:54+00:00

vhost_work_flush doesn't do anything with the work arg. This patch drops it and then renames vhost_work_flush to vhost_work_dev_flush to reflect that the function flushes all the works in the dev and not just a specific queue or work item. Signed-off-by: Mike Christie Acked-by: Jason Wang Reviewed-by: Chaitanya Kulkarni Link: https://lore.kernel.org/r/20210525174733.6212-2-michael.christie@oracle.com Reviewed-by: Stefano Garzarella Signed-off-by: Michael S. Tsirkin