[xen master] x86/microcode: Add missing unlock in microcode_update_helper()

[patchbot@xxxxxxx]

commit b35b22acb887f682efe8385b3df165220bc84c86
Author:     Alejandro Vallejo <alejandro.vallejo@xxxxxxxxx>
AuthorDate: Mon Jun 5 16:01:16 2023 +0100
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Mon Jun 5 16:11:10 2023 +0100

    x86/microcode: Add missing unlock in microcode_update_helper()
    
    microcode_update_helper() may return early while holding
    cpu_add_remove_lock, hence preventing any writers from taking it again.
    
    Leave through the `put` label instead so it's properly released.
    
    Fixes: 5ed12565aa32 ("microcode: rendezvous CPUs in NMI handler and load 
ucode")
    Signed-off-by: Alejandro Vallejo <alejandro.vallejo@xxxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/arch/x86/cpu/microcode/core.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/cpu/microcode/core.c 
b/xen/arch/x86/cpu/microcode/core.c
index c1033f3bc2..e65af4b82e 100644
--- a/xen/arch/x86/cpu/microcode/core.c
+++ b/xen/arch/x86/cpu/microcode/core.c
@@ -599,7 +599,8 @@ static long cf_check microcode_update_helper(void *data)
         printk(XENLOG_WARNING
                "CPU%u is expected to lead ucode loading (but got CPU%u)\n",
                nmi_cpu, cpumask_first(&cpu_online_map));
-        return -EPERM;
+        ret = -EPERM;
+        goto put;
     }
 
     patch = parse_blob(buffer->buffer, buffer->len);
--
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