From f6b29bbd096fc3b1b9ad01e4604feddc9ef2c871 Mon Sep 17 00:00:00 2001 From: Nikunj A Dadhania Date: Wed, 5 Jan 2022 09:33:37 +0530 Subject: [PATCH] KVM: x86: Check for rmaps allocation With TDP MMU being the default now, access to mmu_rmaps_stat debugfs file causes following oops: BUG: kernel NULL pointer dereference, address: 0000000000000000 PGD 0 P4D 0 Oops: 0000 [#1] PREEMPT SMP NOPTI CPU: 7 PID: 3185 Comm: cat Not tainted 5.16.0-rc4+ #204 RIP: 0010:pte_list_count+0x6/0x40 Call Trace: ? kvm_mmu_rmaps_stat_show+0x15e/0x320 seq_read_iter+0x126/0x4b0 ? aa_file_perm+0x124/0x490 seq_read+0xf5/0x140 full_proxy_read+0x5c/0x80 vfs_read+0x9f/0x1a0 ksys_read+0x67/0xe0 __x64_sys_read+0x19/0x20 do_syscall_64+0x3b/0xc0 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7fca6fc13912 Return early when rmaps are not present. Reported-by: Vasant Hegde Tested-by: Vasant Hegde Signed-off-by: Nikunj A Dadhania Reviewed-by: Peter Xu Reviewed-by: Sean Christopherson Message-Id: <20220105040337.4234-1-nikunj@amd.com> Cc: stable@vger.kernel.org Fixes: 15b9954ec9e6 ("KVM: X86: Introduce mmu_rmaps_stat per-vm debugfs file") Signed-off-by: Paolo Bonzini --- arch/x86/kvm/debugfs.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/x86/kvm/debugfs.c b/arch/x86/kvm/debugfs.c index 54a83a7445384..f33c804a922ac 100644 --- a/arch/x86/kvm/debugfs.c +++ b/arch/x86/kvm/debugfs.c @@ -95,6 +95,9 @@ static int kvm_mmu_rmaps_stat_show(struct seq_file *m, void *v) unsigned int *log[KVM_NR_PAGE_SIZES], *cur; int i, j, k, l, ret; + if (!kvm_memslots_have_rmaps(kvm)) + return 0; + ret = -ENOMEM; memset(log, 0, sizeof(log)); for (i = 0; i < KVM_NR_PAGE_SIZES; i++) { -- 2.39.5