This is a note to let you know that I've just added the patch titled x86/hyperv: Fix NULL deref in set_hv_tscchange_cb() if Hyper-V setup fails to the 5.10-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: x86-hyperv-fix-null-deref-in-set_hv_tscchange_cb-if-hyper-v-setup-fails.patch and it can be found in the queue-5.10 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From daf972118c517b91f74ff1731417feb4270625a4 Mon Sep 17 00:00:00 2001 From: Sean Christopherson <seanjc@xxxxxxxxxx> Date: Thu, 4 Nov 2021 18:22:38 +0000 Subject: x86/hyperv: Fix NULL deref in set_hv_tscchange_cb() if Hyper-V setup fails From: Sean Christopherson <seanjc@xxxxxxxxxx> commit daf972118c517b91f74ff1731417feb4270625a4 upstream. Check for a valid hv_vp_index array prior to derefencing hv_vp_index when setting Hyper-V's TSC change callback. If Hyper-V setup failed in hyperv_init(), the kernel will still report that it's running under Hyper-V, but will have silently disabled nearly all functionality. BUG: kernel NULL pointer dereference, address: 0000000000000010 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] SMP CPU: 4 PID: 1 Comm: swapper/0 Not tainted 5.15.0-rc2+ #75 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 RIP: 0010:set_hv_tscchange_cb+0x15/0xa0 Code: <8b> 04 82 8b 15 12 17 85 01 48 c1 e0 20 48 0d ee 00 01 00 f6 c6 08 ... Call Trace: kvm_arch_init+0x17c/0x280 kvm_init+0x31/0x330 vmx_init+0xba/0x13a do_one_initcall+0x41/0x1c0 kernel_init_freeable+0x1f2/0x23b kernel_init+0x16/0x120 ret_from_fork+0x22/0x30 Fixes: 93286261de1b ("x86/hyperv: Reenlightenment notifications support") Cc: stable@xxxxxxxxxxxxxxx Cc: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> Reviewed-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> Link: https://lore.kernel.org/r/20211104182239.1302956-2-seanjc@xxxxxxxxxx Signed-off-by: Wei Liu <wei.liu@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/x86/hyperv/hv_init.c | 3 +++ 1 file changed, 3 insertions(+) --- a/arch/x86/hyperv/hv_init.c +++ b/arch/x86/hyperv/hv_init.c @@ -176,6 +176,9 @@ void set_hv_tscchange_cb(void (*cb)(void return; } + if (!hv_vp_index) + return; + hv_reenlightenment_cb = cb; /* Make sure callback is registered before we write to MSRs */ Patches currently in stable-queue which might be from seanjc@xxxxxxxxxx are queue-5.10/x86-hyperv-fix-null-deref-in-set_hv_tscchange_cb-if-hyper-v-setup-fails.patch