linux-kernel - [PATCH v3 1/6] panic: sys_info: Capture si_bits

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Message-ID: <20251030132007.3742368-2-andriy.shevchenko@linux.intel.com>
Date: Thu, 30 Oct 2025 12:44:17 +0100
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Feng Tang <feng.tang@...ux.alibaba.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	linux-kernel@...r.kernel.org
Cc: Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH v3 1/6] panic: sys_info: Capture si_bits_global before iterating over it

The for-loop might re-read the content of the memory the si_bits_global
points to on each iteration. Instead, just capture it for the sake of
consistency and use that instead.

Reviewed-by: Feng Tang <feng.tang@...ux.alibaba.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
---
 lib/sys_info.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/lib/sys_info.c b/lib/sys_info.c
index 496f9151c9b6..d542a024406a 100644
--- a/lib/sys_info.c
+++ b/lib/sys_info.c
@@ -58,11 +58,11 @@ int sysctl_sys_info_handler(const struct ctl_table *ro_table, int write,
 	char names[sizeof(sys_info_avail)];
 	struct ctl_table table;
 	unsigned long *si_bits_global;
+	unsigned long si_bits;
 
 	si_bits_global = ro_table->data;
 
 	if (write) {
-		unsigned long si_bits;
 		int ret;
 
 		table = *ro_table;
@@ -81,9 +81,12 @@ int sysctl_sys_info_handler(const struct ctl_table *ro_table, int write,
 		char *delim = "";
 		int i, len = 0;
 
+		/* The access to the global value is not synchronized. */
+		si_bits = READ_ONCE(*si_bits_global);
+
 		names[0] = '\0';
 		for (i = 0; i < ARRAY_SIZE(si_names); i++) {
-			if (*si_bits_global & si_names[i].bit) {
+			if (si_bits & si_names[i].bit) {
 				len += scnprintf(names + len, sizeof(names) - len,
 					"%s%s", delim, si_names[i].name);
 				delim = ",";
-- 
2.50.1