From: Nikunj A Dadhania <nikunj@amd.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Peter Xu <peterx@redhat.com>, <kvm@vger.kernel.org>,
<linux-kernel@vger.kernel.org>, <nikunj@amd.com>,
<vasant.hegde@amd.com>, <brijesh.singh@amd.com>
Subject: [PATCH v2] KVM: x86: Check for rmaps allocation
Date: Wed, 5 Jan 2022 09:33:37 +0530 [thread overview]
Message-ID: <20220105040337.4234-1-nikunj@amd.com> (raw)
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:
<TASK>
? 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 <vasant.hegde@amd.com>
Tested-by: Vasant Hegde <vasant.hegde@amd.com>
Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
---
v1: https://lore.kernel.org/kvm/20220104092814.11553-1-nikunj@amd.com/T/#u
Check the rmaps inside kvm_mmu_rmaps_stat_show() as the rmaps can be
allocated dynamically (Peter Xu)
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 543a8c04025c..9240b3b7f8dd 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++) {
--
2.32.0
next reply other threads:[~2022-01-05 4:04 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-05 4:03 Nikunj A Dadhania [this message]
2022-01-05 9:07 ` [PATCH v2] KVM: x86: Check for rmaps allocation Peter Xu
2022-01-07 17:01 ` Sean Christopherson
2022-01-07 17:03 ` Paolo Bonzini
2022-01-07 17:04 ` Paolo Bonzini
2022-01-07 17:08 ` Paolo Bonzini
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