kernel/linux.git/drivers/vhost, branch v6.1.178

vhost/net: complete zerocopy ubufs only once

2026-07-24T13:54:41+00:00

[ Upstream commit 8f6898fe80794f2d7c3d38c1158c806e4074a1c4 ] vhost-net initializes one ubuf_info per outstanding zerocopy TX descriptor and hands it to the backend socket. The networking stack may then clone a zerocopy skb before all skb references are released. For example, batman-adv fragmentation reaches skb_split(), which calls skb_zerocopy_clone() and increments the same ubuf_info refcount. vhost_zerocopy_complete() currently treats every ubuf callback as a completed vhost descriptor. It dereferences ubuf->ctx, writes the descriptor completion state, and drops the vhost_net_ubuf_ref even when the callback only releases a cloned skb reference. A backend reset can therefore wait for and free the vhost_net_ubuf_ref while another cloned skb still carries the same ubuf_info. A later completion then dereferences the freed ubufs pointer. KASAN reports the stale completion as: BUG: KASAN: slab-use-after-free in vhost_zerocopy_complete+0x1d7/0x1f0 BUG: KASAN: slab-use-after-free in vhost_zerocopy_complete+0x101/0x1f0 vhost_zerocopy_complete skb_copy_ubufs __dev_forward_skb2 veth_xmit The freed object was allocated from vhost_net_ioctl() while setting the backend and freed through kfree_rcu()/kvfree_rcu_bulk after backend removal, while delayed skb completion still reached vhost_zerocopy_complete(). Honor the generic ubuf_info refcount before touching vhost state, and run the vhost descriptor completion only for the final ubuf reference. This matches the msg_zerocopy_complete() ownership rule for cloned zerocopy skbs. Fixes: bab632d69ee4 ("vhost: vhost TX zero-copy support") Signed-off-by: Qing Ming Signed-off-by: Michael S. Tsirkin Message-ID: <20260601104300.197210-1-a0yami@mailbox.org> Signed-off-by: Sasha Levin

vhost/vdpa: validate virtqueue index in mmap and fault paths

2026-07-24T13:54:41+00:00

[ Upstream commit 929e4f044621c8cc30b612fb74e1410bef09e41b ] vhost_vdpa_mmap() and vhost_vdpa_fault() use vma->vm_pgoff as a virtqueue index for get_vq_notification(), but they do not validate that the index is smaller than v->nvqs. The ioctl path already performs both a bounds check and array_index_nospec(), but the mmap/fault path only checks that the index fits in u16. This allows an out-of-range queue index to reach driver-specific get_vq_notification() callbacks. Fix this by extracting a unified vhost_vdpa_get_vq_notification() helper that validates the queue index against v->nvqs and applies array_index_nospec() before calling the driver callback. Both the mmap and fault paths use this helper, and the bounds checking is consolidated into a single location. From source inspection, the most defensible impact is out-of-bounds access in the callback path, potentially leading to invalid PFN remaps and crash/DoS. Fixes: ddd89d0a059d ("vhost_vdpa: support doorbell mapping via mmap") Acked-by: Eugenio Pérez Acked-by: Michael S. Tsirkin Signed-off-by: Qihang Tang Signed-off-by: Michael S. Tsirkin Message-ID: <20260508075821.92656-1-q.h.hack.winter@gmail.com> Signed-off-by: Sasha Levin

vhost_net: fix sleeping with preempt-disabled in vhost_net_busy_poll()

2026-06-01T15:39:26+00:00

[ Upstream commit e08a9fac5cf8c3fecf4755e7e3ac059f78b8f83d ] syzbot reported "sleeping function called from invalid context" in vhost_net_busy_poll(). Commit 030881372460 ("vhost_net: basic polling support") introduced a busy-poll loop and preempt_{disable,enable}() around it, where each iteration calls a sleepable function inside the loop. The purpose of disabling preemption was to keep local_clock()-based timeout accounting on a single CPU, rather than as a requirement of busy-poll itself: https://lore.kernel.org/1448435489-5949-4-git-send-email-jasowang@redhat.com From this perspective, migrate_disable() is sufficient here, so replace preempt_disable() with migrate_disable(), avoiding sleepable accesses from a preempt-disabled context. Fixes: 030881372460 ("vhost_net: basic polling support") Tested-by: syzbot+6985cb8e543ea90ba8ee@syzkaller.appspotmail.com Reported-by: syzbot+6985cb8e543ea90ba8ee@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/69e6a414.050a0220.24bfd3.002d.GAE@google.com/T/ Signed-off-by: Kohei Enju Acked-by: Michael S. Tsirkin Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

vhost-scsi: Fix handling of multiple calls to vhost_scsi_set_endpoint

2026-02-06T15:44:24+00:00

[ Upstream commit 5dd639a1646ef5fe8f4bf270fad47c5c3755b9b6 ] If vhost_scsi_set_endpoint is called multiple times without a vhost_scsi_clear_endpoint between them, we can hit multiple bugs found by Haoran Zhang: 1. Use-after-free when no tpgs are found: This fixes a use after free that occurs when vhost_scsi_set_endpoint is called more than once and calls after the first call do not find any tpgs to add to the vs_tpg. When vhost_scsi_set_endpoint first finds tpgs to add to the vs_tpg array match=true, so we will do: vhost_vq_set_backend(vq, vs_tpg); ... kfree(vs->vs_tpg); vs->vs_tpg = vs_tpg; If vhost_scsi_set_endpoint is called again and no tpgs are found match=false so we skip the vhost_vq_set_backend call leaving the pointer to the vs_tpg we then free via: kfree(vs->vs_tpg); vs->vs_tpg = vs_tpg; If a scsi request is then sent we do: vhost_scsi_handle_vq -> vhost_scsi_get_req -> vhost_vq_get_backend which sees the vs_tpg we just did a kfree on. 2. Tpg dir removal hang: This patch fixes an issue where we cannot remove a LIO/target layer tpg (and structs above it like the target) dir due to the refcount dropping to -1. The problem is that if vhost_scsi_set_endpoint detects a tpg is already in the vs->vs_tpg array or if the tpg has been removed so target_depend_item fails, the undepend goto handler will do target_undepend_item on all tpgs in the vs_tpg array dropping their refcount to 0. At this time vs_tpg contains both the tpgs we have added in the current vhost_scsi_set_endpoint call as well as tpgs we added in previous calls which are also in vs->vs_tpg. Later, when vhost_scsi_clear_endpoint runs it will do target_undepend_item on all the tpgs in the vs->vs_tpg which will drop their refcount to -1. Userspace will then not be able to remove the tpg and will hang when it tries to do rmdir on the tpg dir. 3. Tpg leak: This fixes a bug where we can leak tpgs and cause them to be un-removable because the target name is overwritten when vhost_scsi_set_endpoint is called multiple times but with different target names. The bug occurs if a user has called VHOST_SCSI_SET_ENDPOINT and setup a vhost-scsi device to target/tpg mapping, then calls VHOST_SCSI_SET_ENDPOINT again with a new target name that has tpgs we haven't seen before (target1 has tpg1 but target2 has tpg2). When this happens we don't teardown the old target tpg mapping and just overwrite the target name and the vs->vs_tpg array. Later when we do vhost_scsi_clear_endpoint, we are passed in either target1 or target2's name and we will only match that target's tpgs when we loop over the vs->vs_tpg. We will then return from the function without doing target_undepend_item on the tpgs. Because of all these bugs, it looks like being able to call vhost_scsi_set_endpoint multiple times was never supported. The major user, QEMU, already has checks to prevent this use case. So to fix the issues, this patch prevents vhost_scsi_set_endpoint from being called if it's already successfully added tpgs. To add, remove or change the tpg config or target name, you must do a vhost_scsi_clear_endpoint first. Fixes: 25b98b64e284 ("vhost scsi: alloc cmds per vq instead of session") Fixes: 4f7f46d32c98 ("tcm_vhost: Use vq->private_data to indicate if the endpoint is setup") Reported-by: Haoran Zhang Closes: https://lore.kernel.org/virtualization/e418a5ee-45ca-4d18-9b5d-6f8b6b1add8e@oracle.com/T/#me6c0041ce376677419b9b2563494172a01487ecb Signed-off-by: Mike Christie Reviewed-by: Stefan Hajnoczi Message-Id: <20250129210922.121533-1-michael.christie@oracle.com> Signed-off-by: Michael S. Tsirkin Acked-by: Stefano Garzarella [ Minor conflict resolved. ] Signed-off-by: Li hongliang <1468888505@139.com> Signed-off-by: Greg Kroah-Hartman

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

2026-01-11T14:18:50+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: vringh: Modify the return value check

2025-10-15T09:56:39+00:00

[ Upstream commit 82a8d0fda55b35361ee7f35b54fa2b66d7847d2b ] The return value of copy_from_iter and copy_to_iter can't be negative, check whether the copied lengths are equal. Fixes: 309bba39c945 ("vringh: iterate on iotlb_translate to handle large translations") Cc: "Stefano Garzarella" Signed-off-by: zhang jiao Message-Id: <20250910091739.2999-1-zhangjiao2@cmss.chinamobile.com> Signed-off-by: Michael S. Tsirkin Signed-off-by: Sasha Levin

vhost: vringh: Fix copy_to_iter return value check

2025-10-15T09:56:37+00:00

[ Upstream commit 439263376c2c4e126cac0d07e4987568de4eaba5 ] The return value of copy_to_iter can't be negative, check whether the copied length is equal to the requested length instead of checking for negative values. Cc: zhang jiao Link: https://lore.kernel.org/all/20250910091739.2999-1-zhangjiao2@cmss.chinamobile.com Signed-off-by: Michael S. Tsirkin Reviewed-by: Simon Horman Fixes: 309bba39c945 ("vringh: iterate on iotlb_translate to handle large translations") Link: https://patch.msgid.link/cd637504a6e3967954a9e80fc1b75e8c0978087b.1758723310.git.mst@redhat.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

vhost/net: Protect ubufs with rcu read lock in vhost_net_ubuf_put()

2025-09-04T13:26:26+00:00

commit dd54bcf86c91a4455b1f95cbc8e9ac91205f3193 upstream. When operating on struct vhost_net_ubuf_ref, the following execution sequence is theoretically possible: CPU0 is finalizing DMA operation CPU1 is doing VHOST_NET_SET_BACKEND // ubufs->refcount == 2 vhost_net_ubuf_put() vhost_net_ubuf_put_wait_and_free(oldubufs) vhost_net_ubuf_put_and_wait() vhost_net_ubuf_put() int r = atomic_sub_return(1, &ubufs->refcount); // r = 1 int r = atomic_sub_return(1, &ubufs->refcount); // r = 0 wait_event(ubufs->wait, !atomic_read(&ubufs->refcount)); // no wait occurs here because condition is already true kfree(ubufs); if (unlikely(!r)) wake_up(&ubufs->wait); // use-after-free This leads to use-after-free on ubufs access. This happens because CPU1 skips waiting for wake_up() when refcount is already zero. To prevent that use a read-side RCU critical section in vhost_net_ubuf_put(), as suggested by Hillf Danton. For this lock to take effect, free ubufs with kfree_rcu(). Cc: stable@vger.kernel.org Fixes: 0ad8b480d6ee9 ("vhost: fix ref cnt checking deadlock") Reported-by: Andrey Ryabinin Suggested-by: Hillf Danton Signed-off-by: Nikolay Kuratov Message-Id: <20250805130917.727332-1-kniv@yandex-team.ru> Signed-off-by: Michael S. Tsirkin Signed-off-by: Greg Kroah-Hartman

vhost/vsock: Avoid allocating arbitrarily-sized SKBs

2025-08-28T14:26:07+00:00

commit 10a886aaed293c4db3417951f396827216299e3d upstream. vhost_vsock_alloc_skb() returns NULL for packets advertising a length larger than VIRTIO_VSOCK_MAX_PKT_BUF_SIZE in the packet header. However, this is only checked once the SKB has been allocated and, if the length in the packet header is zero, the SKB may not be freed immediately. Hoist the size check before the SKB allocation so that an iovec larger than VIRTIO_VSOCK_MAX_PKT_BUF_SIZE + the header size is rejected outright. The subsequent check on the length field in the header can then simply check that the allocated SKB is indeed large enough to hold the packet. Cc: Fixes: 71dc9ec9ac7d ("virtio/vsock: replace virtio_vsock_pkt with sk_buff") Reviewed-by: Stefano Garzarella Signed-off-by: Will Deacon Message-Id: <20250717090116.11987-2-will@kernel.org> Signed-off-by: Michael S. Tsirkin Signed-off-by: Greg Kroah-Hartman

vhost: fail early when __vhost_add_used() fails

2025-08-28T14:25:59+00:00

[ Upstream commit b4ba1207d45adaafa2982c035898b36af2d3e518 ] This patch fails vhost_add_used_n() early when __vhost_add_used() fails to make sure used idx is not updated with stale used ring information. Reported-by: Eugenio Pérez Signed-off-by: Jason Wang Message-Id: <20250714084755.11921-2-jasowang@redhat.com> Signed-off-by: Michael S. Tsirkin Tested-by: Lei Yang Signed-off-by: Sasha Levin