[xen stable-4.16] x86/microcode: Add missing unlock in microcode_update_helper()

[patchbot@xxxxxxx]

commit d3065bf0a83e02032d0900566fa8605d8865073d
Author:     Alejandro Vallejo <alejandro.vallejo@xxxxxxxxx>
AuthorDate: Mon Jul 17 08:34:11 2023 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Jul 17 08:34:11 2023 +0200

    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>
    master commit: b35b22acb887f682efe8385b3df165220bc84c86
    master date: 2023-06-05 16:11:10 +0100
---
 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 ad150e5963..cd942130f5 100644
--- a/xen/arch/x86/cpu/microcode/core.c
+++ b/xen/arch/x86/cpu/microcode/core.c
@@ -594,7 +594,8 @@ static long 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);
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.16