{ "containers": { "cna": { "providerMetadata": { "orgId": "f4215fc3-5b6b-47ff-a258-f7189bd81038" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: Use dedicated mutex to protect kvm_usage_count to avoid deadlock\n\nUse a dedicated mutex to guard kvm_usage_count to fix a potential deadlock\non x86 due to a chain of locks and SRCU synchronizations. Translating the\nbelow lockdep splat, CPU1 #6 will wait on CPU0 #1, CPU0 #8 will wait on\nCPU2 #3, and CPU2 #7 will wait on CPU1 #4 (if there's a writer, due to the\nfairness of r/w semaphores).\n\n CPU0 CPU1 CPU2\n1 lock(&kvm->slots_lock);\n2 lock(&vcpu->mutex);\n3 lock(&kvm->srcu);\n4 lock(cpu_hotplug_lock);\n5 lock(kvm_lock);\n6 lock(&kvm->slots_lock);\n7 lock(cpu_hotplug_lock);\n8 sync(&kvm->srcu);\n\nNote, there are likely more potential deadlocks in KVM x86, e.g. the same\npattern of taking cpu_hotplug_lock outside of kvm_lock likely exists with\n__kvmclock_cpufreq_notifier():\n\n cpuhp_cpufreq_online()\n |\n -> cpufreq_online()\n |\n -> cpufreq_gov_performance_limits()\n |\n -> __cpufreq_driver_target()\n |\n -> __target_index()\n |\n -> cpufreq_freq_transition_begin()\n |\n -> cpufreq_notify_transition()\n |\n -> ... __kvmclock_cpufreq_notifier()\n\nBut, actually triggering such deadlocks is beyond rare due to the\ncombination of dependencies and timings involved. E.g. the cpufreq\nnotifier is only used on older CPUs without a constant TSC, mucking with\nthe NX hugepage mitigation while VMs are running is very uncommon, and\ndoing so while also onlining/offlining a CPU (necessary to generate\ncontention on cpu_hotplug_lock) would be even more unusual.\n\nThe most robust solution to the general cpu_hotplug_lock issue is likely\nto switch vm_list to be an RCU-protected list, e.g. so that x86's cpufreq\nnotifier doesn't to take kvm_lock. For now, settle for fixing the most\nblatant deadlock, as switching to an RCU-protected list is a much more\ninvolved change, but add a comment in locking.rst to call out that care\nneeds to be taken when walking holding kvm_lock and walking vm_list.\n\n ======================================================\n WARNING: possible circular locking dependency detected\n 6.10.0-smp--c257535a0c9d-pip #330 Tainted: G S O\n ------------------------------------------------------\n tee/35048 is trying to acquire lock:\n ff6a80eced71e0a8 (&kvm->slots_lock){+.+.}-{3:3}, at: set_nx_huge_pages+0x179/0x1e0 [kvm]\n\n but task is already holding lock:\n ffffffffc07abb08 (kvm_lock){+.+.}-{3:3}, at: set_nx_huge_pages+0x14a/0x1e0 [kvm]\n\n which lock already depends on the new lock.\n\n the existing dependency chain (in reverse order) is:\n\n -> #3 (kvm_lock){+.+.}-{3:3}:\n __mutex_lock+0x6a/0xb40\n mutex_lock_nested+0x1f/0x30\n kvm_dev_ioctl+0x4fb/0xe50 [kvm]\n __se_sys_ioctl+0x7b/0xd0\n __x64_sys_ioctl+0x21/0x30\n x64_sys_call+0x15d0/0x2e60\n do_syscall_64+0x83/0x160\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\n -> #2 (cpu_hotplug_lock){++++}-{0:0}:\n cpus_read_lock+0x2e/0xb0\n static_key_slow_inc+0x16/0x30\n kvm_lapic_set_base+0x6a/0x1c0 [kvm]\n kvm_set_apic_base+0x8f/0xe0 [kvm]\n kvm_set_msr_common+0x9ae/0xf80 [kvm]\n vmx_set_msr+0xa54/0xbe0 [kvm_intel]\n __kvm_set_msr+0xb6/0x1a0 [kvm]\n kvm_arch_vcpu_ioctl+0xeca/0x10c0 [kvm]\n kvm_vcpu_ioctl+0x485/0x5b0 [kvm]\n __se_sys_ioctl+0x7b/0xd0\n __x64_sys_ioctl+0x21/0x30\n x64_sys_call+0x15d0/0x2e60\n do_syscall_64+0x83/0x160\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\n -> #1 (&kvm->srcu){.+.+}-{0:0}:\n __synchronize_srcu+0x44/0x1a0\n \n---truncated---" } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "Documentation/virt/kvm/locking.rst", "virt/kvm/kvm_main.c" ], "versions": [ { "version": "0bf50497f03b", "lessThan": "4777225ec89f", "status": "affected", "versionType": "git" }, { "version": "0bf50497f03b", "lessThan": "a2764afce521", "status": "affected", "versionType": "git" }, { "version": "0bf50497f03b", "lessThan": "760a196e6dcb", "status": "affected", "versionType": "git" }, { "version": "0bf50497f03b", "lessThan": "44d174596260", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "Documentation/virt/kvm/locking.rst", "virt/kvm/kvm_main.c" ], "versions": [ { "version": "6.3", "status": "affected" }, { "version": "0", "lessThan": "6.3", "status": "unaffected", "versionType": "custom" }, { "version": "6.6.54", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "custom" }, { "version": "6.10.13", "lessThanOrEqual": "6.10.*", "status": "unaffected", "versionType": "custom" }, { "version": "6.11.2", "lessThanOrEqual": "6.11.*", "status": "unaffected", "versionType": "custom" }, { "version": "6.12-rc1", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/4777225ec89f52bb9ca16a33cfb44c189f1b7b47" }, { "url": "https://git.kernel.org/stable/c/a2764afce521fd9fd7a5ff6ed52ac2095873128a" }, { "url": "https://git.kernel.org/stable/c/760a196e6dcb29580e468b44b5400171dae184d8" }, { "url": "https://git.kernel.org/stable/c/44d17459626052a2390457e550a12cb973506b2f" } ], "title": "KVM: Use dedicated mutex to protect kvm_usage_count to avoid deadlock", "x_generator": { "engine": "bippy-c9c4e1df01b2" } } }, "cveMetadata": { "assignerOrgId": "f4215fc3-5b6b-47ff-a258-f7189bd81038", "cveID": "CVE-2024-47744", "requesterUserId": "gregkh@kernel.org", "serial": "1", "state": "PUBLISHED" }, "dataType": "CVE_RECORD", "dataVersion": "5.0" }