x86/xen/msr: Fix uninitialized variable 'err'

xen_read_msr_safe() currently passes an uninitialized argument 'err' to
xen_do_read_msr(). But as xen_do_read_msr() may not set the argument,
xen_read_msr_safe() could return err with an unpredictable value.

To ensure correctness, initialize err to 0 (representing success)
in xen_read_msr_safe().

Do the same in xen_read_msr(), even err is not used after being passed
to xen_do_read_msr().

Closes: https://lore.kernel.org/xen-devel/aBxNI_Q0-MhtBSZG@stanley.mountain/
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Xin Li (Intel) <xin@zytor.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Juergen Gross <jgross@suse.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Link: https://lore.kernel.org/r/20250517165713.935384-1-xin@zytor.com

diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index 7f9ded1bc707e331a61e6c43ac54707979a4c482..26bbaf4b7330b4981e59467e9b05192b56b04d70 100644 (file)
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -1162,7 +1162,7 @@ static void xen_do_write_msr(u32 msr, u64 val, int *err)
 
 static int xen_read_msr_safe(u32 msr, u64 *val)
 {
-       int err;
+       int err = 0;
 
        *val = xen_do_read_msr(msr, &err);
        return err;
@@ -1179,7 +1179,7 @@ static int xen_write_msr_safe(u32 msr, u64 val)
 
 static u64 xen_read_msr(u32 msr)
 {
-       int err;
+       int err = 0;
 
        return xen_do_read_msr(msr, xen_msr_safe ? &err : NULL);
 }