[xen master] cpuid: initialize cpuinfo with boot_cpu_data

[patchbot@xxxxxxx]

commit 793456d7aa9893d09df55ad2c0986b2a06ea4a98
Author:     Norbert Manthey <nmanthey@xxxxxxxxx>
AuthorDate: Mon Feb 14 10:07:36 2022 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Feb 14 10:07:36 2022 +0100

    cpuid: initialize cpuinfo with boot_cpu_data
    
    When re-identifying CPU data, we might use uninitialized data when
    checking for the cache line property to adapt the cache
    alignment. The data that depends on this uninitialized read is
    currently not forwarded.
    
    To avoid problems in the future, initialize the data cpuinfo
    structure before re-identifying the CPU again.
    
    The trace to hit the uninitialized read reported by Coverity is:
    
    bool recheck_cpu_features(unsigned int cpu)
    ...
        struct cpuinfo_x86 c;
        ...
        identify_cpu(&c);
    
    void identify_cpu(struct cpuinfo_x86 *c)
    ...
        generic_identify(c)
    
    static void generic_identify(struct cpuinfo_x86 *c)
    ...
            if (this_cpu->c_early_init)
                    this_cpu->c_early_init(c); // which is early_init_intel
    
    static void early_init_intel(struct cpuinfo_x86 *c)
    ...
        if (c->x86 == 15 && c->x86_cache_alignment == 64)
            c->x86_cache_alignment = 128;
    
    This bug was discovered and resolved using Coverity Static Analysis
    Security Testing (SAST) by Synopsys, Inc.
    
    Signed-off-by: Norbert Manthey <nmanthey@xxxxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/cpuid.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/arch/x86/cpuid.c b/xen/arch/x86/cpuid.c
index e24dd283e7..7c638eff2b 100644
--- a/xen/arch/x86/cpuid.c
+++ b/xen/arch/x86/cpuid.c
@@ -609,7 +609,7 @@ void __init init_guest_cpuid(void)
 bool recheck_cpu_features(unsigned int cpu)
 {
     bool okay = true;
-    struct cpuinfo_x86 c;
+    struct cpuinfo_x86 c = {0};
     const struct cpuinfo_x86 *bsp = &boot_cpu_data;
     unsigned int i;
 
--
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