From: Sean Christopherson seanjc@google.com

stable inclusion from stable-v4.19.218 commit b20ec58f8a6f4fef32cc71480ddf824584e24743 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9FNFO CVE: CVE-2021-47217

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...

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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@vger.kernel.org Cc: Vitaly Kuznetsov vkuznets@redhat.com Signed-off-by: Sean Christopherson seanjc@google.com Reviewed-by: Vitaly Kuznetsov vkuznets@redhat.com Link: https://lore.kernel.org/r/20211104182239.1302956-2-seanjc@google.com Signed-off-by: Wei Liu wei.liu@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Yu Liao liaoyu15@huawei.com --- arch/x86/hyperv/hv_init.c | 3 +++ 1 file changed, 3 insertions(+)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c index e4ba467a9fc6..fda61a4dc229 100644 --- a/arch/x86/hyperv/hv_init.c +++ b/arch/x86/hyperv/hv_init.c @@ -201,6 +201,9 @@ 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 */