Fix potential vulnerable cloned function#31
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When deassigning a KVM_IRQFD, don't clobber the irqfd's copy of the IRQ's routing entry as doing so breaks kvm_arch_irq_bypass_del_producer() on x86 and arm64, which explicitly look for KVM_IRQ_ROUTING_MSI. Instead, to handle a concurrent routing update, verify that the irqfd is still active before consuming the routing information. As evidenced by the x86 and arm64 bugs, and another bug in kvm_arch_update_irqfd_routing() (see below), clobbering the entry type without notifying arch code is surprising and error prone. As a bonus, checking that the irqfd is active provides a convenient location for documenting _why_ KVM must not consume the routing entry for an irqfd that is in the process of being deassigned: once the irqfd is deleted from the list (which happens *before* the eventfd is detached), it will no longer receive updates via kvm_irq_routing_update(), and so KVM could deliver an event using stale routing information (relative to KVM_SET_GSI_ROUTING returning to userspace). As an even better bonus, explicitly checking for the irqfd being active fixes a similar bug to the one the clobbering is trying to prevent: if an irqfd is deactivated, and then its routing is changed, kvm_irq_routing_update() won't invoke kvm_arch_update_irqfd_routing() (because the irqfd isn't in the list). And so if the irqfd is in bypass mode, IRQs will continue to be posted using the old routing information. As for kvm_arch_irq_bypass_del_producer(), clobbering the routing type results in KVM incorrectly keeping the IRQ in bypass mode, which is especially problematic on AMD as KVM tracks IRQs that are being posted to a vCPU in a list whose lifetime is tied to the irqfd. Without the help of KASAN to detect use-after-free, the most common sympton on AMD is a NULL pointer deref in amd_iommu_update_ga() due to the memory for irqfd structure being re-allocated and zeroed, resulting in irqfd->irq_bypass_data being NULL when read by avic_update_iommu_vcpu_affinity(): BUG: kernel NULL pointer dereference, address: 0000000000000018 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 40cf2b9067 P4D 40cf2b9067 PUD 408362a067 PMD 0 Oops: Oops: 0000 [#1] SMP CPU: 6 UID: 0 PID: 40383 Comm: vfio_irq_test Tainted: G U W O 6.19.0-smp--5dddc257e6b2-irqfd #31 NONE Tainted: [U]=USER, [W]=WARN, [O]=OOT_MODULE Hardware name: Google, Inc. Arcadia_IT_80/Arcadia_IT_80, BIOS 34.78.2-0 09/05/2025 RIP: 0010:amd_iommu_update_ga+0x19/0xe0 Call Trace: <TASK> avic_update_iommu_vcpu_affinity+0x3d/0x90 [kvm_amd] __avic_vcpu_load+0xf4/0x130 [kvm_amd] kvm_arch_vcpu_load+0x89/0x210 [kvm] vcpu_load+0x30/0x40 [kvm] kvm_arch_vcpu_ioctl_run+0x45/0x620 [kvm] kvm_vcpu_ioctl+0x571/0x6a0 [kvm] __se_sys_ioctl+0x6d/0xb0 do_syscall_64+0x6f/0x9d0 entry_SYSCALL_64_after_hwframe+0x4b/0x53 RIP: 0033:0x46893b </TASK> ---[ end trace 0000000000000000 ]--- If AVIC is inhibited when the irfd is deassigned, the bug will manifest as list corruption, e.g. on the next irqfd assignment. list_add corruption. next->prev should be prev (ffff8d474d5cd588), but was 0000000000000000. (next=ffff8d8658f86530). ------------[ cut here ]------------ kernel BUG at lib/list_debug.c:31! Oops: invalid opcode: 0000 [#1] SMP CPU: 128 UID: 0 PID: 80818 Comm: vfio_irq_test Tainted: G U W O 6.19.0-smp--f19dc4d680ba-irqfd #28 NONE Tainted: [U]=USER, [W]=WARN, [O]=OOT_MODULE Hardware name: Google, Inc. Arcadia_IT_80/Arcadia_IT_80, BIOS 34.78.2-0 09/05/2025 RIP: 0010:__list_add_valid_or_report+0x97/0xc0 Call Trace: <TASK> avic_pi_update_irte+0x28e/0x2b0 [kvm_amd] kvm_pi_update_irte+0xbf/0x190 [kvm] kvm_arch_irq_bypass_add_producer+0x72/0x90 [kvm] irq_bypass_register_consumer+0xcd/0x170 [irqbypass] kvm_irqfd+0x4c6/0x540 [kvm] kvm_vm_ioctl+0x118/0x5d0 [kvm] __se_sys_ioctl+0x6d/0xb0 do_syscall_64+0x6f/0x9d0 entry_SYSCALL_64_after_hwframe+0x4b/0x53 </TASK> ---[ end trace 0000000000000000 ]--- On Intel and arm64, the bug is less noisy, as the end result is that the device keeps posting IRQs to the vCPU even after it's been deassigned. Note, the worst of the breakage can be traced back to commit cb21073 ("KVM: Pass new routing entries and irqfd when updating IRTEs"), as before that commit KVM would pull the routing information from the per-VM routing table. But as above, similar bugs have existed since support for IRQ bypass was added. E.g. if a routing change finished before irq_shutdown() invoked kvm_arch_irq_bypass_del_producer(), VMX and SVM would see stale routing information and potentially leave the irqfd in bypass mode. Alternatively, x86 could be fixed by explicitly checking irq_bypass_vcpu instead of irq_entry.type in kvm_arch_irq_bypass_del_producer(), and arm64 could be modified to utilize irq_bypass_vcpu in a similar manner. But (a) that wouldn't fix the routing updates bug, and (b) fixing core code doesn't preclude x86 (or arm64) from adding such code as a sanity check (spoiler alert). Fixes: f70c20a ("KVM: Add an arch specific hooks in 'struct kvm_kernel_irqfd'") Fixes: cb21073 ("KVM: Pass new routing entries and irqfd when updating IRTEs") Fixes: a0d7e2f ("KVM: arm64: vgic-v4: Only attempt vLPI mapping for actual MSIs") Cc: stable@vger.kernel.org Cc: Marc Zyngier <maz@kernel.org> Cc: Oliver Upton <oupton@kernel.org> Link: https://patch.msgid.link/20260113174606.104978-2-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc@google.com>
idryomov
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Mar 13, 2026
…pt_rt' Jiayuan Chen says: ==================== bpf: Fix per-CPU bulk queue races on PREEMPT_RT On PREEMPT_RT kernels, local_bh_disable() only calls migrate_disable() (when PREEMPT_RT_NEEDS_BH_LOCK is not set) and does not disable preemption. This means CFS scheduling can preempt a task inside the per-CPU bulk queue (bq) operations in cpumap and devmap, allowing another task on the same CPU to concurrently access the same bq, leading to use-after-free, list corruption, and kernel panics. Patch 1 fixes the cpumap race in bq_flush_to_queue(), originally reported by syzbot [1]. Patch 2 fixes the same class of race in devmap's bq_xmit_all(), identified by code inspection after Sebastian Andrzej Siewior pointed out that devmap has the same per-CPU bulk queue pattern [2]. Both patches use local_lock_nested_bh() to serialize access to the per-CPU bq. On non-RT this is a pure lockdep annotation with no overhead; on PREEMPT_RT it provides a per-CPU sleeping lock. To reproduce the devmap race, insert an mdelay(100) in bq_xmit_all() after "cnt = bq->count" and before the actual transmit loop. Then pin two threads to the same CPU, each running BPF_PROG_TEST_RUN with an XDP program that redirects to a DEVMAP entry (e.g. a veth pair). CFS timeslicing during the mdelay window causes interleaving. Without the fix, KASAN reports null-ptr-deref due to operating on freed frames: BUG: KASAN: null-ptr-deref in __build_skb_around+0x22d/0x340 Write of size 32 at addr 0000000000000d50 by task devmap_race_rep/449 CPU: 0 UID: 0 PID: 449 Comm: devmap_race_rep Not tainted 6.19.0+ #31 PREEMPT_RT Call Trace: <TASK> __build_skb_around+0x22d/0x340 build_skb_around+0x25/0x260 __xdp_build_skb_from_frame+0x103/0x860 veth_xdp_rcv_bulk_skb.isra.0+0x162/0x320 veth_xdp_rcv.constprop.0+0x61e/0xbb0 veth_poll+0x280/0xb50 __napi_poll.constprop.0+0xa5/0x590 net_rx_action+0x4b0/0xea0 handle_softirqs.isra.0+0x1b3/0x780 __local_bh_enable_ip+0x12a/0x240 xdp_test_run_batch.constprop.0+0xedd/0x1f60 bpf_test_run_xdp_live+0x304/0x640 bpf_prog_test_run_xdp+0xd24/0x1b70 __sys_bpf+0x61c/0x3e00 </TASK> Kernel panic - not syncing: Fatal exception in interrupt [1] https://lore.kernel.org/all/69369331.a70a0220.38f243.009d.GAE@google.com/T/ [2] https://lore.kernel.org/bpf/20260212023634.366343-1-jiayuan.chen@linux.dev/ v3 -> v4: https://lore.kernel.org/all/20260213034018.284146-1-jiayuan.chen@linux.dev/ - Move panic trace to cover letter. (Sebastian Andrzej Siewior) - Add Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> to both patches from cover letter. v2 -> v3: https://lore.kernel.org/bpf/20260212023634.366343-1-jiayuan.chen@linux.dev/ - Fix commit message: remove incorrect "spin_lock() becomes rt_mutex" claim, the per-CPU bq has no spin_lock at all. (Sebastian Andrzej Siewior) - Fix commit message: accurately describe local_lock_nested_bh() behavior instead of referencing local_lock(). (Sebastian Andrzej Siewior) - Remove incomplete discussion of snapshot alternative. (Sebastian Andrzej Siewior) - Remove panic trace from commit message. (Sebastian Andrzej Siewior) - Add patch 2/2 for devmap, same race pattern. (Sebastian Andrzej Siewior) v1 -> v2: https://lore.kernel.org/bpf/20260211064417.196401-1-jiayuan.chen@linux.dev/ - Use local_lock_nested_bh()/local_unlock_nested_bh() instead of local_lock()/local_unlock(), since these paths already run under local_bh_disable(). (Sebastian Andrzej Siewior) - Replace "Caller must hold bq->bq_lock" comment with lockdep_assert_held() in bq_flush_to_queue(). (Sebastian Andrzej Siewior) - Fix Fixes tag to 3253cb4 ("softirq: Allow to drop the softirq-BKL lock on PREEMPT_RT") which is the actual commit that makes the race possible. (Sebastian Andrzej Siewior) ==================== Link: https://patch.msgid.link/20260225121459.183121-1-jiayuan.chen@linux.dev Signed-off-by: Alexei Starovoitov <ast@kernel.org>
idryomov
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May 11, 2026
…g FLR During Function Level Reset recovery, the MANA driver reads hardware BAR0 registers that may temporarily contain garbage values. The SHM (Shared Memory) offset read from GDMA_REG_SHM_OFFSET is used to compute gc->shm_base, which is later dereferenced via readl() in mana_smc_poll_register(). If the hardware returns an unaligned or out-of-range value, the driver must not blindly use it, as this would propagate the hardware error into a kernel crash. The following crash was observed on an arm64 Hyper-V guest running kernel 6.17.0-3013-azure during VF reset recovery triggered by HWC timeout. [13291.785274] Unable to handle kernel paging request at virtual address ffff8000a200001b [13291.785311] Mem abort info: [13291.785332] ESR = 0x0000000096000021 [13291.785343] EC = 0x25: DABT (current EL), IL = 32 bits [13291.785355] SET = 0, FnV = 0 [13291.785363] EA = 0, S1PTW = 0 [13291.785372] FSC = 0x21: alignment fault [13291.785382] Data abort info: [13291.785391] ISV = 0, ISS = 0x00000021, ISS2 = 0x00000000 [13291.785404] CM = 0, WnR = 0, TnD = 0, TagAccess = 0 [13291.785412] GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 [13291.785421] swapper pgtable: 4k pages, 48-bit VAs, pgdp=00000014df3a1000 [13291.785432] [ffff8000a200001b] pgd=1000000100438403, p4d=1000000100438403, pud=1000000100439403, pmd=0068000fc2000711 [13291.785703] Internal error: Oops: 0000000096000021 [#1] SMP [13291.830975] Modules linked in: tls qrtr mana_ib ib_uverbs ib_core xt_owner xt_tcpudp xt_conntrack nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 nft_compat nf_tables cfg80211 8021q garp mrp stp llc binfmt_misc joydev serio_raw nls_iso8859_1 hid_generic aes_ce_blk aes_ce_cipher polyval_ce ghash_ce sm4_ce_gcm sm4_ce_ccm sm4_ce sm4_ce_cipher hid_hyperv sm4 sm3_ce sha3_ce hv_netvsc hid vmgenid hyperv_keyboard hyperv_drm sch_fq_codel nvme_fabrics efi_pstore dm_multipath nfnetlink vsock_loopback vmw_vsock_virtio_transport_common hv_sock vmw_vsock_vmci_transport vmw_vmci vsock dmi_sysfs ip_tables x_tables autofs4 [13291.862630] CPU: 122 UID: 0 PID: 61796 Comm: kworker/122:2 Tainted: G W 6.17.0-3013-azure #13-Ubuntu VOLUNTARY [13291.869902] Tainted: [W]=WARN [13291.871901] Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS Hyper-V UEFI Release v4.1 01/08/2026 [13291.878086] Workqueue: events mana_serv_func [13291.880718] pstate: 62400005 (nZCv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--) [13291.884835] pc : mana_smc_poll_register+0x48/0xb0 [13291.887902] lr : mana_smc_setup_hwc+0x70/0x1c0 [13291.890493] sp : ffff8000ab79bbb0 [13291.892364] x29: ffff8000ab79bbb0 x28: ffff00410c8b5900 x27: ffff00410d630680 [13291.896252] x26: ffff004171f9fd80 x25: 000000016ed55000 x24: 000000017f37e000 [13291.899990] x23: 0000000000000000 x22: 000000016ed55000 x21: 0000000000000000 [13291.904497] x20: ffff8000a200001b x19: 0000000000004e20 x18: ffff8000a6183050 [13291.908308] x17: 0000000000000000 x16: 0000000000000000 x15: 000000000000000a [13291.912542] x14: 0000000000000004 x13: 0000000000000000 x12: 0000000000000000 [13291.916298] x11: 0000000000000000 x10: 0000000000000001 x9 : ffffc45006af1bd8 [13291.920945] x8 : ffff000151129000 x7 : 0000000000000000 x6 : 0000000000000000 [13291.925293] x5 : 000000015f214000 x4 : 000000017217a000 x3 : 000000016ed50000 [13291.930436] x2 : 000000016ed55000 x1 : 0000000000000000 x0 : ffff8000a1ffffff [13291.934342] Call trace: [13291.935736] mana_smc_poll_register+0x48/0xb0 (P) [13291.938611] mana_smc_setup_hwc+0x70/0x1c0 [13291.941113] mana_hwc_create_channel+0x1a0/0x3a0 [13291.944283] mana_gd_setup+0x16c/0x398 [13291.946584] mana_gd_resume+0x24/0x70 [13291.948917] mana_do_service+0x13c/0x1d0 [13291.951583] mana_serv_func+0x34/0x68 [13291.953732] process_one_work+0x168/0x3d0 [13291.956745] worker_thread+0x2ac/0x480 [13291.959104] kthread+0xf8/0x110 [13291.961026] ret_from_fork+0x10/0x20 [13291.963560] Code: d2807d00 9417c551 71000673 54000220 (b9400281) [13291.967299] ---[ end trace 0000000000000000 ]--- Disassembly of mana_smc_poll_register() around the crash site: Disassembly of section .text: 00000000000047c8 <mana_smc_poll_register>: 47c8: d503201f nop 47cc: d503201f nop 47d0: d503233f paciasp 47d4: f800865e str x30, [x18], #8 47d8: a9bd7bfd stp x29, x30, [sp, #-48]! 47dc: 910003fd mov x29, sp 47e0: a90153f3 stp x19, x20, [sp, #16] 47e4: 91007014 add x20, x0, #0x1c 47e8: 5289c413 mov w19, #0x4e20 47ec: f90013f5 str x21, [sp, #32] 47f0: 12001c35 and w21, w1, #0xff 47f4: 14000008 b 4814 <mana_smc_poll_register+0x4c> 47f8: 36f801e1 tbz w1, #31, 4834 <mana_smc_poll_register+0x6c> 47fc: 52800042 mov w2, #0x2 4800: d280fa01 mov x1, #0x7d0 4804: d2807d00 mov x0, #0x3e8 4808: 94000000 bl 0 <usleep_range_state> 480c: 71000673 subs w19, w19, #0x1 4810: 54000200 b.eq 4850 <mana_smc_poll_register+0x88> 4814: b9400281 ldr w1, [x20] <-- **** CRASHED HERE ***** 4818: d50331bf dmb oshld 481c: 2a0103e2 mov w2, w1 ... From the crash signature x20 = ffff8000a200001b, this address ends in 0x1b which is not 4-byte aligned, so the 'ldr w1, [x20]' instruction (readl) triggers the arm64 alignment fault (FSC = 0x21). The root cause is in mana_gd_init_vf_regs(), which computes: gc->shm_base = gc->bar0_va + mana_gd_r64(gc, GDMA_REG_SHM_OFFSET); The offset is used without any validation. The same problem exists in mana_gd_init_pf_regs() for sriov_base_off and sriov_shm_off. Fix this by validating all offsets before use: - VF: check shm_off is within BAR0, properly aligned to 4 bytes (readl requirement), and leaves room for the full 256-bit (32-byte) SMC aperture. - PF: check sriov_base_off is within BAR0, aligned to 8 bytes (readq requirement), and leaves room to safely read the sriov_shm_off register at sriov_base_off + GDMA_PF_REG_SHM_OFF. Then check sriov_shm_off leaves room for the full SMC aperture. All arithmetic uses subtraction rather than addition to avoid integer overflow on garbage values. Define SMC_APERTURE_SIZE (32 bytes, derived from the 256-bit aperture width) Return -EPROTO on invalid values. The existing recovery path in mana_serv_reset() already handles -EPROTO by falling through to PCI device rescan, giving the hardware another chance to present valid register values after reset. Fixes: 9bf6603 ("net: mana: Handle hardware recovery events when probing the device") Signed-off-by: Dipayaan Roy <dipayanroy@linux.microsoft.com> Link: https://patch.msgid.link/afQUMClyjmBVfD+u@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net Signed-off-by: Paolo Abeni <pabeni@redhat.com>
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Hi again,
Our tool identified a potential vulnerability in a clone function in
drivers/net/hamradio/mkiss.csourced from torvalds/linux. These issues, originally reported in CVE-2022-1195, were resolved in the repository via this commit torvalds/linux@b2f37ae.This PR applies the corresponding patch to fix the vulnerabilities in this codebase.
Please review at your convenience. Thank you for your time and attention!