linux-kernel - [PATCH v4 tip/core/rcu 14/15] kcsan: Fix function matching in report

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Date:   Wed, 15 Apr 2020 11:34:10 -0700
From:   paulmck@...nel.org
To:     linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
        kernel-team@...com, mingo@...nel.org
Cc:     elver@...gle.com, andreyknvl@...gle.com, glider@...gle.com,
        dvyukov@...gle.com, cai@....pw, boqun.feng@...il.com,
        "Paul E . McKenney" <paulmck@...nel.org>
Subject: [PATCH v4 tip/core/rcu 14/15] kcsan: Fix function matching in report

From: Marco Elver <elver@...gle.com>

Pass string length as returned by scnprintf() to strnstr(), since
strnstr() searches exactly len bytes in haystack, even if it contains a
NUL-terminator before haystack+len.

Signed-off-by: Marco Elver <elver@...gle.com>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 kernel/kcsan/report.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/kernel/kcsan/report.c b/kernel/kcsan/report.c
index ddc18f1..cf41d63d 100644
--- a/kernel/kcsan/report.c
+++ b/kernel/kcsan/report.c
@@ -192,11 +192,11 @@ skip_report(enum kcsan_value_change value_change, unsigned long top_frame)
 		 * maintainers.
 		 */
 		char buf[64];
+		int len = scnprintf(buf, sizeof(buf), "%ps", (void *)top_frame);
 
-		snprintf(buf, sizeof(buf), "%ps", (void *)top_frame);
-		if (!strnstr(buf, "rcu_", sizeof(buf)) &&
-		    !strnstr(buf, "_rcu", sizeof(buf)) &&
-		    !strnstr(buf, "_srcu", sizeof(buf)))
+		if (!strnstr(buf, "rcu_", len) &&
+		    !strnstr(buf, "_rcu", len) &&
+		    !strnstr(buf, "_srcu", len))
 			return true;
 	}
 
@@ -262,15 +262,15 @@ static const char *get_thread_desc(int task_id)
 static int get_stack_skipnr(const unsigned long stack_entries[], int num_entries)
 {
 	char buf[64];
+	int len;
 	int skip = 0;
 
 	for (; skip < num_entries; ++skip) {
-		snprintf(buf, sizeof(buf), "%ps", (void *)stack_entries[skip]);
-		if (!strnstr(buf, "csan_", sizeof(buf)) &&
-		    !strnstr(buf, "tsan_", sizeof(buf)) &&
-		    !strnstr(buf, "_once_size", sizeof(buf))) {
+		len = scnprintf(buf, sizeof(buf), "%ps", (void *)stack_entries[skip]);
+		if (!strnstr(buf, "csan_", len) &&
+		    !strnstr(buf, "tsan_", len) &&
+		    !strnstr(buf, "_once_size", len))
 			break;
-		}
 	}
 	return skip;
 }
-- 
2.9.5