linux-kernel - [PATCH v1 2/3] x86/xen/msr: Fix uninitialized symbol 'err'

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Message-ID: <20250512084552.1586883-3-xin@zytor.com>
Date: Mon, 12 May 2025 01:45:51 -0700
From: "Xin Li (Intel)" <xin@...or.com>
To: linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org,
        linux-acpi@...r.kernel.org
Cc: tglx@...utronix.de, mingo@...nel.org, bp@...en8.de,
        dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
        peterz@...radead.org, jgross@...e.com, boris.ostrovsky@...cle.com,
        rafael@...nel.org, lenb@...nel.org
Subject: [PATCH v1 2/3] x86/xen/msr: Fix uninitialized symbol '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().

Because xen_read_msr_safe() is essentially a wrapper of xen_do_read_msr(),
the latter should be responsible for initializing the value of *err to 0.
Thus initialize *err to 0 in xen_do_read_msr().

Fixes: 502ad6e5a619 ("x86/msr: Change the function type of native_read_msr_safe()")
Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
Closes: https://lore.kernel.org/xen-devel/aBxNI_Q0-MhtBSZG@stanley.mountain/
Signed-off-by: Xin Li (Intel) <xin@...or.com>
---
 arch/x86/xen/enlighten_pv.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index 3be38350f044..01f1d441347e 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -1091,6 +1091,9 @@ static u64 xen_do_read_msr(u32 msr, int *err)
 {
 	u64 val = 0;	/* Avoid uninitialized value for safe variant. */
 
+	if (err)
+		*err = 0;
+
 	if (pmu_msr_chk_emulated(msr, &val, true))
 		return val;
 
@@ -1162,7 +1165,7 @@ 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;
-- 
2.49.0