[tip: x86/core] x86/xen/msr: Fix uninitialized variable 'err'

[tip-bot2 for Xin Li (Intel)]

The following commit has been merged into the x86/core branch of tip:

Commit-ID:     54c2c688cd9305bdbab4883b9da6ff63f4deca5d
Gitweb:        https://git.kernel.org/tip/54c2c688cd9305bdbab4883b9da6ff63f4deca5d
Author:        Xin Li (Intel) <xin@xxxxxxxxx>
AuthorDate:    Sat, 17 May 2025 09:57:12 -07:00
Committer:     Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Sun, 18 May 2025 08:39:16 +02:00

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/
Fixes: d815da84fdd0 ("x86/msr: Change the function type of native_read_msr_safe()"
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Signed-off-by: Xin Li (Intel) <xin@xxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Reviewed-by: Juergen Gross <jgross@xxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Link: https://lore.kernel.org/r/20250517165713.935384-1-xin@xxxxxxxxx
---
 arch/x86/xen/enlighten_pv.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index 7f9ded1..26bbaf4 100644
--- 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);
 }