From 9a11997e757bcf716c1b199ea7bd1abbadc4b357 Mon Sep 17 00:00:00 2001 From: Wanpeng Li Date: Mon, 2 Mar 2020 15:15:36 +0800 Subject: KVM: X86: Fix dereference null cpufreq policy Naresh Kamboju reported: Linux version 5.6.0-rc4 (oe-user@oe-host) (gcc version (GCC)) #1 SMP Sun Mar 1 22:59:08 UTC 2020 kvm: no hardware support BUG: kernel NULL pointer dereference, address: 000000000000028c #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] SMP NOPTI CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.6.0-rc4 #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), 04/01/2014 RIP: 0010:kobject_put+0x12/0x1c0 Call Trace: cpufreq_cpu_put+0x15/0x20 kvm_arch_init+0x1f6/0x2b0 kvm_init+0x31/0x290 ? svm_check_processor_compat+0xd/0xd ? svm_check_processor_compat+0xd/0xd svm_init+0x21/0x23 do_one_initcall+0x61/0x2f0 ? rdinit_setup+0x30/0x30 ? rcu_read_lock_sched_held+0x4f/0x80 kernel_init_freeable+0x219/0x279 ? rest_init+0x250/0x250 kernel_init+0xe/0x110 ret_from_fork+0x27/0x50 Modules linked in: CR2: 000000000000028c ---[ end trace 239abf40c55c409b ]--- RIP: 0010:kobject_put+0x12/0x1c0 cpufreq policy which is get by cpufreq_cpu_get() can be NULL if it is failure, this patch takes care of it. Fixes: aaec7c03de (KVM: x86: avoid useless copy of cpufreq policy) Reported-by: Naresh Kamboju Cc: Naresh Kamboju Signed-off-by: Wanpeng Li Signed-off-by: Paolo Bonzini --- arch/x86/kvm/x86.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 5de200663f51..3156e25b0774 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -7195,10 +7195,12 @@ static void kvm_timer_init(void) cpu = get_cpu(); policy = cpufreq_cpu_get(cpu); - if (policy && policy->cpuinfo.max_freq) - max_tsc_khz = policy->cpuinfo.max_freq; + if (policy) { + if (policy->cpuinfo.max_freq) + max_tsc_khz = policy->cpuinfo.max_freq; + cpufreq_cpu_put(policy); + } put_cpu(); - cpufreq_cpu_put(policy); #endif cpufreq_register_notifier(&kvmclock_cpufreq_notifier_block, CPUFREQ_TRANSITION_NOTIFIER); -- cgit v1.2.3-58-ga151