From 4617721c502b2ddaa4e324e86da4997edf738fa5 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 2 Sep 2026 09:55:01 -0400 Subject: ftrace: Synchronize the initialization of ftrace_ops There's some internal state that ftrace_ops needs to have set, but since it can be declared outside of the ftrace.c code, it calls ftrace_ops_init() on the ops in every global function. The issue is that if two tasks call it on the same ops at the same time it is possible to have the initialization of one corrupt the initialization of the other call. Create a ops_mutex to use to synchronize every initialization of the ftrace_ops. The mutex is taken within checking the ftrace_ops flag that states it was initializied but the flag is checked again after the mutex has been taken. Checking first outside the mutex allows it to shortcut having to take the mutex. But then the check needs to be done again after the mute is taken in case of races. Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock") Reported-by: sashiko-bot@kernel.org Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/ Signed-off-by: Steven Rostedt --- lib/sys_info.c | 166 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 166 insertions(+) create mode 100644 lib/sys_info.c (limited to 'lib/sys_info.c') diff --git a/lib/sys_info.c b/lib/sys_info.c new file mode 100644 index 000000000..f32a06ec9 --- /dev/null +++ b/lib/sys_info.c @@ -0,0 +1,166 @@ +// SPDX-License-Identifier: GPL-2.0-only +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include + +static const char * const si_names[] = { + [ilog2(SYS_INFO_TASKS)] = "tasks", + [ilog2(SYS_INFO_MEM)] = "mem", + [ilog2(SYS_INFO_TIMERS)] = "timers", + [ilog2(SYS_INFO_LOCKS)] = "locks", + [ilog2(SYS_INFO_FTRACE)] = "ftrace", + [ilog2(SYS_INFO_PANIC_CONSOLE_REPLAY)] = "", + [ilog2(SYS_INFO_ALL_BT)] = "all_bt", + [ilog2(SYS_INFO_BLOCKED_TASKS)] = "blocked_tasks", +}; + +/* + * Default kernel sys_info mask. + * If a kernel module calls sys_info() with "parameter == 0", then + * this mask will be used. + */ +static unsigned long kernel_si_mask; + +/* Expecting string like "xxx_sys_info=tasks,mem,timers,locks,ftrace,..." */ +unsigned long sys_info_parse_param(char *str) +{ + unsigned long si_bits = 0; + char *s, *name; + int i; + + s = str; + while ((name = strsep(&s, ",")) && *name) { + i = match_string(si_names, ARRAY_SIZE(si_names), name); + if (i >= 0) + __set_bit(i, &si_bits); + } + + return si_bits; +} + +#ifdef CONFIG_SYSCTL + +static int sys_info_write_handler(const struct ctl_table *table, + void *buffer, size_t *lenp, loff_t *ppos, + unsigned long *si_bits_global) +{ + unsigned long si_bits; + int ret; + + ret = proc_dostring(table, 1, buffer, lenp, ppos); + if (ret) + return ret; + + si_bits = sys_info_parse_param(table->data); + + /* The access to the global value is not synchronized. */ + WRITE_ONCE(*si_bits_global, si_bits); + + return 0; +} + +static int sys_info_read_handler(const struct ctl_table *table, + void *buffer, size_t *lenp, loff_t *ppos, + unsigned long *si_bits_global) +{ + unsigned long si_bits; + unsigned int len = 0; + char *delim = ""; + unsigned int i; + + /* The access to the global value is not synchronized. */ + si_bits = READ_ONCE(*si_bits_global); + + for_each_set_bit(i, &si_bits, ARRAY_SIZE(si_names)) { + if (*si_names[i]) { + len += scnprintf(table->data + len, table->maxlen - len, + "%s%s", delim, si_names[i]); + delim = ","; + } + } + + return proc_dostring(table, 0, buffer, lenp, ppos); +} + +int sysctl_sys_info_handler(const struct ctl_table *ro_table, int write, + void *buffer, size_t *lenp, + loff_t *ppos) +{ + struct ctl_table table; + unsigned int i; + size_t maxlen; + + maxlen = 0; + for (i = 0; i < ARRAY_SIZE(si_names); i++) + maxlen += strlen(si_names[i]) + 1; + + char *names __free(kfree) = kzalloc(maxlen, GFP_KERNEL); + if (!names) + return -ENOMEM; + + table = *ro_table; + table.data = names; + table.maxlen = maxlen; + + if (write) + return sys_info_write_handler(&table, buffer, lenp, ppos, ro_table->data); + else + return sys_info_read_handler(&table, buffer, lenp, ppos, ro_table->data); +} + +static const struct ctl_table sys_info_sysctls[] = { + { + .procname = "kernel_sys_info", + .data = &kernel_si_mask, + .maxlen = sizeof(kernel_si_mask), + .mode = 0644, + .proc_handler = sysctl_sys_info_handler, + }, +}; + +static int __init sys_info_sysctl_init(void) +{ + register_sysctl_init("kernel", sys_info_sysctls); + return 0; +} +subsys_initcall(sys_info_sysctl_init); +#endif + +static void __sys_info(unsigned long si_mask) +{ + if (si_mask & SYS_INFO_TASKS) + show_state(); + + if (si_mask & SYS_INFO_MEM) + show_mem(); + + if (si_mask & SYS_INFO_TIMERS) + sysrq_timer_list_show(); + + if (si_mask & SYS_INFO_LOCKS) + debug_show_all_locks(); + + if (si_mask & SYS_INFO_FTRACE) + ftrace_dump(DUMP_ALL); + + if (si_mask & SYS_INFO_ALL_BT) + trigger_all_cpu_backtrace(); + + if (si_mask & SYS_INFO_BLOCKED_TASKS) + show_state_filter(TASK_UNINTERRUPTIBLE); +} + +void sys_info(unsigned long si_mask) +{ + __sys_info(si_mask ? : kernel_si_mask); +} -- cgit v1.3.1