From: Andy Shevchenko Date: Thu, 30 Oct 2025 11:44:17 +0000 (+0100) Subject: panic: sys_info: capture si_bits_global before iterating over it X-Git-Tag: v6.19-rc1~70^2~105 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d79a3aeb747c17095d679cc4402d87f0e7c3405e;p=thirdparty%2Fkernel%2Flinux.git panic: sys_info: capture si_bits_global before iterating over it Patch series "panic: sys_info: Refactor and fix a potential issue", v3. While targeting the compilation issue due to dangling variable, I have noticed more opportunities for refactoring that helps to avoid above mentioned compilation issue in a cleaner way and also fixes a potential problem with global variable access. This patch (of 6): 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. Link: https://lkml.kernel.org/r/20251030132007.3742368-1-andriy.shevchenko@linux.intel.com Link: https://lkml.kernel.org/r/20251030132007.3742368-2-andriy.shevchenko@linux.intel.com Signed-off-by: Andy Shevchenko Reviewed-by: Feng Tang Reviewed-by: Petr Mladek Signed-off-by: Andrew Morton --- diff --git a/lib/sys_info.c b/lib/sys_info.c index 496f9151c9b68..d542a024406a5 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 = ",";