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
Create mmu_rmaps_stat debugfs file only when rmaps are created.
Reported-by: Vasant Hegde <vasant.hegde@xxxxxxx>
Tested-by: Vasant Hegde <vasant.hegde@xxxxxxx>
Signed-off-by: Nikunj A Dadhania <nikunj@xxxxxxx>
---
arch/x86/kvm/debugfs.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/debugfs.c b/arch/x86/kvm/debugfs.c
index 543a8c04025c..78bb09a3a7b7 100644
--- a/arch/x86/kvm/debugfs.c
+++ b/arch/x86/kvm/debugfs.c
@@ -180,7 +180,8 @@ static const struct file_operations mmu_rmaps_stat_fops = {
int kvm_arch_create_vm_debugfs(struct kvm *kvm)
{
- debugfs_create_file("mmu_rmaps_stat", 0644, kvm->debugfs_dentry, kvm,
- &mmu_rmaps_stat_fops);
+ if (kvm_memslots_have_rmaps(kvm))
+ debugfs_create_file("mmu_rmaps_stat", 0644, kvm->debugfs_dentry, kvm,
+ &mmu_rmaps_stat_fops);
return 0;
}
--
2.32.0
