Search Results (607 CVEs found)

CVE Vendors Products Updated CVSS v3.1
CVE-2026-12539 1 Docker 1 Docker Sandboxes 2026-08-13 N/A
Docker Sandboxes (sbx) blocks ICMP egress with an authorizer applied only at network-creation time, and does not re-apply it to networks rebuilt from disk when the Docker daemon restarts, so a restart-surviving sandbox forwards ICMP to arbitrary hosts. A workload inside a sandbox, which the threat model treats as untrusted, can therefore defeat the documented ICMP egress block to perform network reconnaissance and exfiltrate data over an ICMP covert channel, regardless of the configured allowlist.
CVE-2026-20734 1 Intel 1 Amt 2026-08-13 N/A
Improper initialization in some firmware for some Intel(R) Active Management Technology (Intel(R) AMT), and some Intel(R) Standard Manageability may allow an information disclosure. System software adversary with a privileged user combined with a low complexity attack may enable data exposure. This result may potentially occur via local access when attack requirements are present without special internal knowledge and requires no user interaction. The potential vulnerability may impact the confidentiality (high), integrity (none) and availability (none) of the vulnerable system, resulting in subsequent system confidentiality (none), integrity (none) and availability (none) impacts.
CVE-2026-68437 1 Linux 1 Linux Kernel 2026-08-12 5.5 Medium
In the Linux kernel, the following vulnerability has been resolved: drm/imagination: Fit paired fragment job in the correct CCCB For geometry jobs with a paired fragment job, at the moment, the DRM scheduler's prepare_job() callback: - checks for internal (driver) dependencies for the geometry job; - calls into pvr_queue_get_paired_frag_job_dep() to check for external dependencies for the fragment job (the two jobs are submitted together but the common scheduler code doesn't know about it, so this needs to be done at this point in time); - calls into the prepare_job() callback again, but for the fragment job, to check its internal dependencies as well, passing the fragment job's drm_sched_job and the geometry job's drm_sched_entity / pvr_queue. The problem with the last step is that pvr_queue_prepare_job() doesn't always take the mismatched fragment job and geometry queue into account, in particular when checking whether there is space for the fragment command to be submitted, so the code ends up checking for space in the geometry (i.e. wrong) CCCB. The rest of the nested prepare_job() callback happens to work fine at the moment as the other internal dependencies are not relevant for a paired fragment job. Move the initialisation of a paired fragment job's done fence and CCCB fence to pvr_queue_get_paired_frag_job_dep(), inferring the correct queue from the fragment job itself. This fixes cases where prepare_job() wrongly assumed that there was enough space for a paired fragment job in its own CCCB, unblocking run_job(), which then returned early without writing the full sequence of commands to the CCCB. The above lead to kernel warnings such as the following and potentially job timeouts (depending on waiters on the missing commands): [ 552.421075] WARNING: drivers/gpu/drm/imagination/pvr_cccb.c:178 at pvr_cccb_write_command_with_header+0x2c4/0x330 [powervr], CPU#2: kworker/u16:5/63 [ 552.421230] Modules linked in: [ 552.421592] CPU: 2 UID: 0 PID: 63 Comm: kworker/u16:5 Tainted: G W 7.0.0-rc2-gc5d053e4dccb #39 PREEMPT [ 552.421625] Tainted: [W]=WARN [ 552.421637] Hardware name: Texas Instruments AM625 SK (DT) [ 552.421655] Workqueue: powervr-sched drm_sched_run_job_work [gpu_sched] [ 552.421744] pstate: 80000005 (Nzcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) [ 552.421766] pc : pvr_cccb_write_command_with_header+0x2c4/0x330 [powervr] [ 552.421850] lr : pvr_queue_submit_job_to_cccb+0x57c/0xa74 [powervr] [ 552.421923] sp : ffff800084c47650 [ 552.421936] x29: ffff800084c47740 x28: 0000000000000df8 x27: ffff800088a77000 [ 552.421979] x26: 0000000000000030 x25: ffff800084c47680 x24: 0000000000001000 [ 552.422017] x23: ffff800084c47820 x22: 1ffff00010988ecc x21: 0000000000000008 [ 552.422055] x20: 0000000000000208 x19: ffff000006ad5a88 x18: 0000000000000000 [ 552.422093] x17: 0000000020020000 x16: 0000000000020000 x15: 0000000000000000 [ 552.422130] x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000 [ 552.422167] x11: 000000000000f2f2 x10: 00000000f3000000 x9 : 00000000f3f3f3f3 [ 552.422204] x8 : 00000000f2f2f200 x7 : ffff700010988ecc x6 : 0000000000000008 [ 552.422241] x5 : 0000000000000000 x4 : 1ffff0001114ee00 x3 : 0000000000000000 [ 552.422278] x2 : 0000000000000007 x1 : 0000000000000fff x0 : 000000000000002f [ 552.422316] Call trace: [ 552.422330] pvr_cccb_write_command_with_header+0x2c4/0x330 [powervr] (P) [ 552.422411] pvr_queue_submit_job_to_cccb+0x57c/0xa74 [powervr] [ 552.422486] pvr_queue_run_job+0x3a4/0x990 [powervr] [ 552.422562] drm_sched_run_job_work+0x580/0xd48 [gpu_sched] [ 552.422623] process_one_work+0x520/0x1288 [ 552.422657] worker_thread+0x3f0/0xb3c [ 552.422679] kthread+0x334/0x3d8 [ 552.422706] ret_from_fork+0x10/0x20
CVE-2026-68122 1 Linux 1 Linux Kernel 2026-08-10 5.9 Medium
In the Linux kernel, the following vulnerability has been resolved: ovpn: fix peer refcount leak in TCP error paths When either the TCP RX or TX error path calls ovpn_peer_hold() followed by schedule_work(&peer->tcp.defer_del_work), and the work item is already pending from the other path, schedule_work() returns false and the work runs only once. Since ovpn_tcp_peer_del_work() calls ovpn_peer_put() exactly once, the extra reference taken by the losing path is never dropped, leaking the peer object. The race window: CPU0 (strparser/RX error): CPU1 (tcp_tx_work/TX error): ovpn_peer_hold() <- refcnt+1 ovpn_peer_hold() <- refcnt+2 schedule_work() <- queued schedule_work() <- NO-OP (work already pending) ovpn_tcp_peer_del_work runs: ovpn_peer_del() ovpn_peer_put() <- refcnt+1 <- peer never freed Fix by checking the return value of schedule_work() in both paths and calling ovpn_peer_put() to drop the extra reference if the work was already pending. ovpn_peer_hold() is kept unconditional in the TX path as it cannot fail at that point.
CVE-2026-68133 1 Linux 1 Linux Kernel 2026-08-10 5.5 Medium
In the Linux kernel, the following vulnerability has been resolved: ice: fix PTP Call Trace during PTP release If a PF reset occurs when the PTP state is ICE_PTP_UNINIT, then ice_ptp_rebuild() will update the state to ICE_PTP_ERROR. This will result in the following PTP release call trace during driver unload: kernel BUG at lib/list_debug.c:52! ice_ptp_release+0x332/0x3c0 [ice] ice_deinit_features.part.0+0x10e/0x120 [ice] ice_remove+0x100/0x220 [ice] This was observed when passing PF1 through to a VM. ice_ptp_init() fails because ctrl_pf is NULL and sets the state to ICE_PTP_UNINIT. Fix by detecting the ICE_PTP_UNINIT state in ice_ptp_rebuild() and returning without error, preventing the invalid state transition to ICE_PTP_ERROR. The only valid path to ICE_PTP_ERROR is from ICE_PTP_RESETTING after a failed rebuild.
CVE-2026-64602 1 Linux 1 Linux Kernel 2026-08-06 N/A
In the Linux kernel, the following vulnerability has been resolved: iio: adc: spear: Initialize completion before requesting IRQ In the report from Jaeyoung Chung: "spear_adc_probe() in drivers/iio/adc/spear_adc.c registers its interrupt handler with devm_request_irq() before it initializes st->completion with init_completion(). If an interrupt arrives after devm_request_irq() and before init_completion(), the handler calls complete() on an uninitialized completion, causing a kernel panic. The probe path, in spear_adc_probe(): iodev = devm_iio_device_alloc(&pdev->dev, sizeof(*st)); /* st kzalloc-zeroed */ ... retval = devm_request_irq(&pdev->dev, irq, spear_adc_isr, 0, LPC32XXAD_NAME, st); /* register handler */ ... init_completion(&st->completion); /* initialize completion */ spear_adc_isr() calls complete(): complete(&st->completion); If the device raises an interrupt before init_completion() runs, complete() acquires the uninitialized wait.lock and walks the zeroed task_list in swake_up_locked(). The zeroed task_list makes list_empty() return false, so swake_up_locked() dereferences a NULL list entry, triggering a KASAN wild-memory-access." Fix the chance of a spurious IRQ causing an uninitialized pointer dereference by moving init_completion() above devm_request_irq().
CVE-2026-64775 1 Apple 7 Ios And Ipados, Ipados, Iphone Os and 4 more 2026-08-04 9.8 Critical
A memory initialization issue was addressed with improved memory handling. This issue is fixed in iOS 26.6 and iPadOS 26.6, macOS Sequoia 15.7.8, macOS Sonoma 14.8.8, macOS Tahoe 26.6, tvOS 26.6, visionOS 26.6, watchOS 26.6. An app may be able to cause unexpected system termination.
CVE-2024-56641 1 Linux 1 Linux Kernel 2026-08-04 7.5 High
In the Linux kernel, the following vulnerability has been resolved: net/smc: initialize close_work early to avoid warning We encountered a warning that close_work was canceled before initialization. WARNING: CPU: 7 PID: 111103 at kernel/workqueue.c:3047 __flush_work+0x19e/0x1b0 Workqueue: events smc_lgr_terminate_work [smc] RIP: 0010:__flush_work+0x19e/0x1b0 Call Trace: ? __wake_up_common+0x7a/0x190 ? work_busy+0x80/0x80 __cancel_work_timer+0xe3/0x160 smc_close_cancel_work+0x1a/0x70 [smc] smc_close_active_abort+0x207/0x360 [smc] __smc_lgr_terminate.part.38+0xc8/0x180 [smc] process_one_work+0x19e/0x340 worker_thread+0x30/0x370 ? process_one_work+0x340/0x340 kthread+0x117/0x130 ? __kthread_cancel_work+0x50/0x50 ret_from_fork+0x22/0x30 This is because when smc_close_cancel_work is triggered, e.g. the RDMA driver is rmmod and the LGR is terminated, the conn->close_work is flushed before initialization, resulting in WARN_ON(!work->func). __smc_lgr_terminate | smc_connect_{rdma|ism} ------------------------------------------------------------- | smc_conn_create | \- smc_lgr_register_conn for conn in lgr->conns_all | \- smc_conn_kill | \- smc_close_active_abort | \- smc_close_cancel_work | \- cancel_work_sync | \- __flush_work | (close_work) | | smc_close_init | \- INIT_WORK(&close_work) So fix this by initializing close_work before establishing the connection.
CVE-2024-50077 2 Linux, Redhat 2 Linux Kernel, Enterprise Linux 2026-08-04 7.8 High
In the Linux kernel, the following vulnerability has been resolved: Bluetooth: ISO: Fix multiple init when debugfs is disabled If bt_debugfs is not created successfully, which happens if either CONFIG_DEBUG_FS or CONFIG_DEBUG_FS_ALLOW_ALL is unset, then iso_init() returns early and does not set iso_inited to true. This means that a subsequent call to iso_init() will result in duplicate calls to proto_register(), bt_sock_register(), etc. With CONFIG_LIST_HARDENED and CONFIG_BUG_ON_DATA_CORRUPTION enabled, the duplicate call to proto_register() triggers this BUG(): list_add double add: new=ffffffffc0b280d0, prev=ffffffffbab56250, next=ffffffffc0b280d0. ------------[ cut here ]------------ kernel BUG at lib/list_debug.c:35! Oops: invalid opcode: 0000 [#1] PREEMPT SMP PTI CPU: 2 PID: 887 Comm: bluetoothd Not tainted 6.10.11-1-ao-desktop #1 RIP: 0010:__list_add_valid_or_report+0x9a/0xa0 ... __list_add_valid_or_report+0x9a/0xa0 proto_register+0x2b5/0x340 iso_init+0x23/0x150 [bluetooth] set_iso_socket_func+0x68/0x1b0 [bluetooth] kmem_cache_free+0x308/0x330 hci_sock_sendmsg+0x990/0x9e0 [bluetooth] __sock_sendmsg+0x7b/0x80 sock_write_iter+0x9a/0x110 do_iter_readv_writev+0x11d/0x220 vfs_writev+0x180/0x3e0 do_writev+0xca/0x100 ... This change removes the early return. The check for iso_debugfs being NULL was unnecessary, it is always NULL when iso_inited is false.
CVE-2024-46697 2 Linux, Redhat 2 Linux Kernel, Enterprise Linux 2026-08-04 9.8 Critical
In the Linux kernel, the following vulnerability has been resolved: nfsd: ensure that nfsd4_fattr_args.context is zeroed out If nfsd4_encode_fattr4 ends up doing a "goto out" before we get to checking for the security label, then args.context will be set to uninitialized junk on the stack, which we'll then try to free. Initialize it early.
CVE-2024-40925 2 Linux, Redhat 2 Linux Kernel, Enterprise Linux 2026-08-04 7.8 High
In the Linux kernel, the following vulnerability has been resolved: block: fix request.queuelist usage in flush Friedrich Weber reported a kernel crash problem and bisected to commit 81ada09cc25e ("blk-flush: reuse rq queuelist in flush state machine"). The root cause is that we use "list_move_tail(&rq->queuelist, pending)" in the PREFLUSH/POSTFLUSH sequences. But rq->queuelist.next == xxx since it's popped out from plug->cached_rq in __blk_mq_alloc_requests_batch(). We don't initialize its queuelist just for this first request, although the queuelist of all later popped requests will be initialized. Fix it by changing to use "list_add_tail(&rq->queuelist, pending)" so rq->queuelist doesn't need to be initialized. It should be ok since rq can't be on any list when PREFLUSH or POSTFLUSH, has no move actually. Please note the commit 81ada09cc25e ("blk-flush: reuse rq queuelist in flush state machine") also has another requirement that no drivers would touch rq->queuelist after blk_mq_end_request() since we will reuse it to add rq to the post-flush pending list in POSTFLUSH. If this is not true, we will have to revert that commit IMHO. This updated version adds "list_del_init(&rq->queuelist)" in flush rq callback since the dm layer may submit request of a weird invalid format (REQ_FSEQ_PREFLUSH | REQ_FSEQ_POSTFLUSH), which causes double list_add if without this "list_del_init(&rq->queuelist)". The weird invalid format problem should be fixed in dm layer.
CVE-2024-38663 2 Linux, Redhat 3 Linux Kernel, Enterprise Linux, Rhel Eus 2026-08-04 7.8 High
In the Linux kernel, the following vulnerability has been resolved: blk-cgroup: fix list corruption from resetting io stat Since commit 3b8cc6298724 ("blk-cgroup: Optimize blkcg_rstat_flush()"), each iostat instance is added to blkcg percpu list, so blkcg_reset_stats() can't reset the stat instance by memset(), otherwise the llist may be corrupted. Fix the issue by only resetting the counter part.
CVE-2024-38564 2 Linux, Redhat 6 Linux Kernel, Enterprise Linux, Rhel Aus and 3 more 2026-08-04 7.8 High
In the Linux kernel, the following vulnerability has been resolved: bpf: Add BPF_PROG_TYPE_CGROUP_SKB attach type enforcement in BPF_LINK_CREATE bpf_prog_attach uses attach_type_to_prog_type to enforce proper attach type for BPF_PROG_TYPE_CGROUP_SKB. link_create uses bpf_prog_get and relies on bpf_prog_attach_check_attach_type to properly verify prog_type <> attach_type association. Add missing attach_type enforcement for the link_create case. Otherwise, it's currently possible to attach cgroup_skb prog types to other cgroup hooks.
CVE-2024-38558 2 Linux, Redhat 3 Linux Kernel, Enterprise Linux, Rhel Eus 2026-08-04 10 Critical
In the Linux kernel, the following vulnerability has been resolved: net: openvswitch: fix overwriting ct original tuple for ICMPv6 OVS_PACKET_CMD_EXECUTE has 3 main attributes: - OVS_PACKET_ATTR_KEY - Packet metadata in a netlink format. - OVS_PACKET_ATTR_PACKET - Binary packet content. - OVS_PACKET_ATTR_ACTIONS - Actions to execute on the packet. OVS_PACKET_ATTR_KEY is parsed first to populate sw_flow_key structure with the metadata like conntrack state, input port, recirculation id, etc. Then the packet itself gets parsed to populate the rest of the keys from the packet headers. Whenever the packet parsing code starts parsing the ICMPv6 header, it first zeroes out fields in the key corresponding to Neighbor Discovery information even if it is not an ND packet. It is an 'ipv6.nd' field. However, the 'ipv6' is a union that shares the space between 'nd' and 'ct_orig' that holds the original tuple conntrack metadata parsed from the OVS_PACKET_ATTR_KEY. ND packets should not normally have conntrack state, so it's fine to share the space, but normal ICMPv6 Echo packets or maybe other types of ICMPv6 can have the state attached and it should not be overwritten. The issue results in all but the last 4 bytes of the destination address being wiped from the original conntrack tuple leading to incorrect packet matching and potentially executing wrong actions in case this packet recirculates within the datapath or goes back to userspace. ND fields should not be accessed in non-ND packets, so not clearing them should be fine. Executing memset() only for actual ND packets to avoid the issue. Initializing the whole thing before parsing is needed because ND packet may not contain all the options. The issue only affects the OVS_PACKET_CMD_EXECUTE path and doesn't affect packets entering OVS datapath from network interfaces, because in this case CT metadata is populated from skb after the packet is already parsed.
CVE-2024-33619 1 Linux 1 Linux Kernel 2026-08-04 7.8 High
In the Linux kernel, the following vulnerability has been resolved: efi: libstub: only free priv.runtime_map when allocated priv.runtime_map is only allocated when efi_novamap is not set. Otherwise, it is an uninitialized value. In the error path, it is freed unconditionally. Avoid passing an uninitialized value to free_pool. Free priv.runtime_map only when it was allocated. This bug was discovered and resolved using Coverity Static Analysis Security Testing (SAST) by Synopsys, Inc.
CVE-2021-47261 1 Linux 1 Linux Kernel 2026-08-04 7.8 High
In the Linux kernel, the following vulnerability has been resolved: IB/mlx5: Fix initializing CQ fragments buffer The function init_cq_frag_buf() can be called to initialize the current CQ fragments buffer cq->buf, or the temporary cq->resize_buf that is filled during CQ resize operation. However, the offending commit started to use function get_cqe() for getting the CQEs, the issue with this change is that get_cqe() always returns CQEs from cq->buf, which leads us to initialize the wrong buffer, and in case of enlarging the CQ we try to access elements beyond the size of the current cq->buf and eventually hit a kernel panic. [exception RIP: init_cq_frag_buf+103] [ffff9f799ddcbcd8] mlx5_ib_resize_cq at ffffffffc0835d60 [mlx5_ib] [ffff9f799ddcbdb0] ib_resize_cq at ffffffffc05270df [ib_core] [ffff9f799ddcbdc0] llt_rdma_setup_qp at ffffffffc0a6a712 [llt] [ffff9f799ddcbe10] llt_rdma_cc_event_action at ffffffffc0a6b411 [llt] [ffff9f799ddcbe98] llt_rdma_client_conn_thread at ffffffffc0a6bb75 [llt] [ffff9f799ddcbec8] kthread at ffffffffa66c5da1 [ffff9f799ddcbf50] ret_from_fork_nospec_begin at ffffffffa6d95ddd Fix it by getting the needed CQE by calling mlx5_frag_buf_get_wqe() that takes the correct source buffer as a parameter.
CVE-2026-54409 1 Ui 1 Unifi Protect 2026-07-31 7.5 High
A malicious actor with access to the network and under certain conditions could exploit an Improper Initialization vulnerability found in UniFi Protect Application to bypass authentication in UniFi Protect Cameras.
CVE-2025-21949 1 Linux 1 Linux Kernel 2026-07-30 7.8 High
In the Linux kernel, the following vulnerability has been resolved: LoongArch: Set hugetlb mmap base address aligned with pmd size With ltp test case "testcases/bin/hugefork02", there is a dmesg error report message such as: kernel BUG at mm/hugetlb.c:5550! Oops - BUG[#1]: CPU: 0 UID: 0 PID: 1517 Comm: hugefork02 Not tainted 6.14.0-rc2+ #241 Hardware name: QEMU QEMU Virtual Machine, BIOS unknown 2/2/2022 pc 90000000004eaf1c ra 9000000000485538 tp 900000010edbc000 sp 900000010edbf940 a0 900000010edbfb00 a1 9000000108d20280 a2 00007fffe9474000 a3 00007ffff3474000 a4 0000000000000000 a5 0000000000000003 a6 00000000003cadd3 a7 0000000000000000 t0 0000000001ffffff t1 0000000001474000 t2 900000010ecd7900 t3 00007fffe9474000 t4 00007fffe9474000 t5 0000000000000040 t6 900000010edbfb00 t7 0000000000000001 t8 0000000000000005 u0 90000000004849d0 s9 900000010edbfa00 s0 9000000108d20280 s1 00007fffe9474000 s2 0000000002000000 s3 9000000108d20280 s4 9000000002b38b10 s5 900000010edbfb00 s6 00007ffff3474000 s7 0000000000000406 s8 900000010edbfa08 ra: 9000000000485538 unmap_vmas+0x130/0x218 ERA: 90000000004eaf1c __unmap_hugepage_range+0x6f4/0x7d0 PRMD: 00000004 (PPLV0 +PIE -PWE) EUEN: 00000007 (+FPE +SXE +ASXE -BTE) ECFG: 00071c1d (LIE=0,2-4,10-12 VS=7) ESTAT: 000c0000 [BRK] (IS= ECode=12 EsubCode=0) PRID: 0014c010 (Loongson-64bit, Loongson-3A5000) Process hugefork02 (pid: 1517, threadinfo=00000000a670eaf4, task=000000007a95fc64) Call Trace: [<90000000004eaf1c>] __unmap_hugepage_range+0x6f4/0x7d0 [<9000000000485534>] unmap_vmas+0x12c/0x218 [<9000000000494068>] exit_mmap+0xe0/0x308 [<900000000025fdc4>] mmput+0x74/0x180 [<900000000026a284>] do_exit+0x294/0x898 [<900000000026aa30>] do_group_exit+0x30/0x98 [<900000000027bed4>] get_signal+0x83c/0x868 [<90000000002457b4>] arch_do_signal_or_restart+0x54/0xfa0 [<90000000015795e8>] irqentry_exit_to_user_mode+0xb8/0x138 [<90000000002572d0>] tlb_do_page_fault_1+0x114/0x1b4 The problem is that base address allocated from hugetlbfs is not aligned with pmd size. Here add a checking for hugetlbfs and align base address with pmd size. After this patch the test case "testcases/bin/hugefork02" passes to run. This is similar to the commit 7f24cbc9c4d42db8a3c8484d1 ("mm/mmap: teach generic_get_unmapped_area{_topdown} to handle hugetlb mappings").
CVE-2025-21906 1 Linux 1 Linux Kernel 2026-07-30 7.6 High
In the Linux kernel, the following vulnerability has been resolved: wifi: iwlwifi: mvm: clean up ROC on failure If the firmware fails to start the session protection, then we do call iwl_mvm_roc_finished() here, but that won't do anything at all because IWL_MVM_STATUS_ROC_P2P_RUNNING was never set. Set IWL_MVM_STATUS_ROC_P2P_RUNNING in the failure/stop path. If it started successfully before, it's already set, so that doesn't matter, and if it didn't start it needs to be set to clean up. Not doing so will lead to a WARN_ON() later on a fresh remain- on-channel, since the link is already active when activated as it was never deactivated.
CVE-2025-21839 1 Linux 1 Linux Kernel 2026-07-30 7.3 High
In the Linux kernel, the following vulnerability has been resolved: KVM: x86: Load DR6 with guest value only before entering .vcpu_run() loop Move the conditional loading of hardware DR6 with the guest's DR6 value out of the core .vcpu_run() loop to fix a bug where KVM can load hardware with a stale vcpu->arch.dr6. When the guest accesses a DR and host userspace isn't debugging the guest, KVM disables DR interception and loads the guest's values into hardware on VM-Enter and saves them on VM-Exit. This allows the guest to access DRs at will, e.g. so that a sequence of DR accesses to configure a breakpoint only generates one VM-Exit. For DR0-DR3, the logic/behavior is identical between VMX and SVM, and also identical between KVM_DEBUGREG_BP_ENABLED (userspace debugging the guest) and KVM_DEBUGREG_WONT_EXIT (guest using DRs), and so KVM handles loading DR0-DR3 in common code, _outside_ of the core kvm_x86_ops.vcpu_run() loop. But for DR6, the guest's value doesn't need to be loaded into hardware for KVM_DEBUGREG_BP_ENABLED, and SVM provides a dedicated VMCB field whereas VMX requires software to manually load the guest value, and so loading the guest's value into DR6 is handled by {svm,vmx}_vcpu_run(), i.e. is done _inside_ the core run loop. Unfortunately, saving the guest values on VM-Exit is initiated by common x86, again outside of the core run loop. If the guest modifies DR6 (in hardware, when DR interception is disabled), and then the next VM-Exit is a fastpath VM-Exit, KVM will reload hardware DR6 with vcpu->arch.dr6 and clobber the guest's actual value. The bug shows up primarily with nested VMX because KVM handles the VMX preemption timer in the fastpath, and the window between hardware DR6 being modified (in guest context) and DR6 being read by guest software is orders of magnitude larger in a nested setup. E.g. in non-nested, the VMX preemption timer would need to fire precisely between #DB injection and the #DB handler's read of DR6, whereas with a KVM-on-KVM setup, the window where hardware DR6 is "dirty" extends all the way from L1 writing DR6 to VMRESUME (in L1). L1's view: ========== <L1 disables DR interception> CPU 0/KVM-7289 [023] d.... 2925.640961: kvm_entry: vcpu 0 A: L1 Writes DR6 CPU 0/KVM-7289 [023] d.... 2925.640963: <hack>: Set DRs, DR6 = 0xffff0ff1 B: CPU 0/KVM-7289 [023] d.... 2925.640967: kvm_exit: vcpu 0 reason EXTERNAL_INTERRUPT intr_info 0x800000ec D: L1 reads DR6, arch.dr6 = 0 CPU 0/KVM-7289 [023] d.... 2925.640969: <hack>: Sync DRs, DR6 = 0xffff0ff0 CPU 0/KVM-7289 [023] d.... 2925.640976: kvm_entry: vcpu 0 L2 reads DR6, L1 disables DR interception CPU 0/KVM-7289 [023] d.... 2925.640980: kvm_exit: vcpu 0 reason DR_ACCESS info1 0x0000000000000216 CPU 0/KVM-7289 [023] d.... 2925.640983: kvm_entry: vcpu 0 CPU 0/KVM-7289 [023] d.... 2925.640983: <hack>: Set DRs, DR6 = 0xffff0ff0 L2 detects failure CPU 0/KVM-7289 [023] d.... 2925.640987: kvm_exit: vcpu 0 reason HLT L1 reads DR6 (confirms failure) CPU 0/KVM-7289 [023] d.... 2925.640990: <hack>: Sync DRs, DR6 = 0xffff0ff0 L0's view: ========== L2 reads DR6, arch.dr6 = 0 CPU 23/KVM-5046 [001] d.... 3410.005610: kvm_exit: vcpu 23 reason DR_ACCESS info1 0x0000000000000216 CPU 23/KVM-5046 [001] ..... 3410.005610: kvm_nested_vmexit: vcpu 23 reason DR_ACCESS info1 0x0000000000000216 L2 => L1 nested VM-Exit CPU 23/KVM-5046 [001] ..... 3410.005610: kvm_nested_vmexit_inject: reason: DR_ACCESS ext_inf1: 0x0000000000000216 CPU 23/KVM-5046 [001] d.... 3410.005610: kvm_entry: vcpu 23 CPU 23/KVM-5046 [001] d.... 3410.005611: kvm_exit: vcpu 23 reason VMREAD CPU 23/KVM-5046 [001] d.... 3410.005611: kvm_entry: vcpu 23 CPU 23/KVM-5046 [001] d.... 3410. ---truncated---