linux-kernel - [PATCH 1/7] cpumask: fix checking valid cpu range

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Message-Id: <20220919210559.1509179-2-yury.norov@gmail.com>
Date:   Mon, 19 Sep 2022 14:05:53 -0700
From:   Yury Norov <yury.norov@...il.com>
To:     linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Yury Norov <yury.norov@...il.com>
Subject: [PATCH 1/7] cpumask: fix checking valid cpu range

The range of valid CPUs is [0, nr_cpu_ids). Some cpumask functions are
passed with a shifted CPU index, and for them, the valid range is
[-1, nr_cpu_ids-1). Currently for those functions, we check the index
against [-1, nr_cpu_ids), which is wrong.

Signed-off-by: Yury Norov <yury.norov@...il.com>
---
 include/linux/cpumask.h | 19 ++++++++-----------
 1 file changed, 8 insertions(+), 11 deletions(-)

diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index e4f9136a4a63..a1cd4eb1a3d6 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -174,9 +174,8 @@ static inline unsigned int cpumask_last(const struct cpumask *srcp)
 static inline
 unsigned int cpumask_next(int n, const struct cpumask *srcp)
 {
-	/* -1 is a legal arg here. */
-	if (n != -1)
-		cpumask_check(n);
+	/* n is a prior cpu */
+	cpumask_check(n + 1);
 	return find_next_bit(cpumask_bits(srcp), nr_cpumask_bits, n + 1);
 }
 
@@ -189,9 +188,8 @@ unsigned int cpumask_next(int n, const struct cpumask *srcp)
  */
 static inline unsigned int cpumask_next_zero(int n, const struct cpumask *srcp)
 {
-	/* -1 is a legal arg here. */
-	if (n != -1)
-		cpumask_check(n);
+	/* n is a prior cpu */
+	cpumask_check(n + 1);
 	return find_next_zero_bit(cpumask_bits(srcp), nr_cpumask_bits, n+1);
 }
 
@@ -231,9 +229,8 @@ static inline
 unsigned int cpumask_next_and(int n, const struct cpumask *src1p,
 		     const struct cpumask *src2p)
 {
-	/* -1 is a legal arg here. */
-	if (n != -1)
-		cpumask_check(n);
+	/* n is a prior cpu */
+	cpumask_check(n + 1);
 	return find_next_and_bit(cpumask_bits(src1p), cpumask_bits(src2p),
 		nr_cpumask_bits, n + 1);
 }
@@ -267,8 +264,8 @@ static inline
 unsigned int cpumask_next_wrap(int n, const struct cpumask *mask, int start, bool wrap)
 {
 	cpumask_check(start);
-	if (n != -1)
-		cpumask_check(n);
+	/* n is a prior cpu */
+	cpumask_check(n + 1);
 
 	/*
 	 * Return the first available CPU when wrapping, or when starting before cpu0,
-- 
2.34.1