x86/cpu: Initialize MSR_TSC_AUX if RDTSCP *or* RDPID is supported

stable inclusion
from stable-5.10.36
commit 3aec683ee79b5bfb343d9e01d1bb2cac1d627d50
bugzilla: 51867
CVE: NA

--------------------------------

commit b6b4fbd9 upstream.

Initialize MSR_TSC_AUX with CPU node information if RDTSCP or RDPID is
supported.  This fixes a bug where vdso_read_cpunode() will read garbage
via RDPID if RDPID is supported but RDTSCP is not.  While no known CPU
supports RDPID but not RDTSCP, both Intel's SDM and AMD's APM allow for
RDPID to exist without RDTSCP, e.g. it's technically a legal CPU model
for a virtual machine.

Note, technically MSR_TSC_AUX could be initialized if and only if RDPID
is supported since RDTSCP is currently not used to retrieve the CPU node.
But, the cost of the superfluous WRMSR is negigible, whereas leaving
MSR_TSC_AUX uninitialized is just asking for future breakage if someone
decides to utilize RDTSCP.

Fixes: a582c540 ("x86/vdso: Use RDPID in preference to LSL when available")
Signed-off-by: NSean Christopherson <seanjc@google.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20210504225632.1532621-2-seanjc@google.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NWeilong Chen <chenweilong@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

arch/x86/kernel/cpu/common.c

@@ -1847,7 +1847,7 @@ static inline void setup_getcpu(int cpu)
 	unsigned long cpudata = vdso_encode_cpunode(cpu, early_cpu_to_node(cpu));
 	struct desc_struct d = { };
 
-	if (boot_cpu_has(X86_FEATURE_RDTSCP))
+	if (boot_cpu_has(X86_FEATURE_RDTSCP) || boot_cpu_has(X86_FEATURE_RDPID))
 		write_rdtscp_aux(cpudata);
 
 	/* Store CPU and node number in limit. */