This is a note to let you know that I've just added the patch titled KVM: x86: Check for rmaps allocation to the 5.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: kvm-x86-check-for-rmaps-allocation.patch and it can be found in the queue-5.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From fffb5323780786c81ba005f8b8603d4a558aad28 Mon Sep 17 00:00:00 2001 From: Nikunj A Dadhania <nikunj@xxxxxxx> Date: Wed, 5 Jan 2022 09:33:37 +0530 Subject: KVM: x86: Check for rmaps allocation From: Nikunj A Dadhania <nikunj@xxxxxxx> commit fffb5323780786c81ba005f8b8603d4a558aad28 upstream. 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@xxxxxxx> Tested-by: Vasant Hegde <vasant.hegde@xxxxxxx> Signed-off-by: Nikunj A Dadhania <nikunj@xxxxxxx> Reviewed-by: Peter Xu <peterx@xxxxxxxxxx> Reviewed-by: Sean Christopherson <seanjc@xxxxxxxxxx> Message-Id: <20220105040337.4234-1-nikunj@xxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Fixes: 3bcd0662d66f ("KVM: X86: Introduce mmu_rmaps_stat per-vm debugfs file") Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/x86/kvm/debugfs.c | 3 +++ 1 file changed, 3 insertions(+) --- a/arch/x86/kvm/debugfs.c +++ b/arch/x86/kvm/debugfs.c @@ -95,6 +95,9 @@ static int kvm_mmu_rmaps_stat_show(struc 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++) { Patches currently in stable-queue which might be from nikunj@xxxxxxx are queue-5.15/kvm-x86-check-for-rmaps-allocation.patch