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64ae572bc7
Reading the sched_cmdline_ref and sched_tgid_ref initial state within
tracing_start_sched_switch without holding the sched_register_mutex is
racy against concurrent updates, which can lead to tracepoint probes
being registered more than once (and thus trigger warnings within
tracepoint.c).
[ May be the fix for this bug ]
Link: https://lore.kernel.org/r/000000000000ab6f84056c786b93@google.com
Link: http://lkml.kernel.org/r/20190817141208.15226-1-mathieu.desnoyers@efficios.com
Cc: stable@vger.kernel.org
CC: Steven Rostedt (VMware) <rostedt@goodmis.org>
CC: Joel Fernandes (Google) <joel@joelfernandes.org>
CC: Peter Zijlstra <peterz@infradead.org>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Paul E. McKenney <paulmck@linux.ibm.com>
Reported-by: syzbot+774fddf07b7ab29a1e55@syzkaller.appspotmail.com
Fixes: d914ba37d7 ("tracing: Add support for recording tgid of tasks")
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
149 lines
3.1 KiB
C
149 lines
3.1 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* trace context switch
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*
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* Copyright (C) 2007 Steven Rostedt <srostedt@redhat.com>
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*
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*/
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#include <linux/module.h>
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#include <linux/kallsyms.h>
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#include <linux/uaccess.h>
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#include <linux/ftrace.h>
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#include <trace/events/sched.h>
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#include "trace.h"
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#define RECORD_CMDLINE 1
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#define RECORD_TGID 2
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static int sched_cmdline_ref;
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static int sched_tgid_ref;
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static DEFINE_MUTEX(sched_register_mutex);
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static void
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probe_sched_switch(void *ignore, bool preempt,
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struct task_struct *prev, struct task_struct *next)
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{
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int flags;
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flags = (RECORD_TGID * !!sched_tgid_ref) +
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(RECORD_CMDLINE * !!sched_cmdline_ref);
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if (!flags)
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return;
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tracing_record_taskinfo_sched_switch(prev, next, flags);
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}
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static void
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probe_sched_wakeup(void *ignore, struct task_struct *wakee)
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{
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int flags;
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flags = (RECORD_TGID * !!sched_tgid_ref) +
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(RECORD_CMDLINE * !!sched_cmdline_ref);
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if (!flags)
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return;
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tracing_record_taskinfo(current, flags);
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}
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static int tracing_sched_register(void)
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{
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int ret;
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ret = register_trace_sched_wakeup(probe_sched_wakeup, NULL);
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if (ret) {
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pr_info("wakeup trace: Couldn't activate tracepoint"
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" probe to kernel_sched_wakeup\n");
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return ret;
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}
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ret = register_trace_sched_wakeup_new(probe_sched_wakeup, NULL);
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if (ret) {
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pr_info("wakeup trace: Couldn't activate tracepoint"
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" probe to kernel_sched_wakeup_new\n");
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goto fail_deprobe;
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}
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ret = register_trace_sched_switch(probe_sched_switch, NULL);
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if (ret) {
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pr_info("sched trace: Couldn't activate tracepoint"
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" probe to kernel_sched_switch\n");
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goto fail_deprobe_wake_new;
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}
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return ret;
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fail_deprobe_wake_new:
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unregister_trace_sched_wakeup_new(probe_sched_wakeup, NULL);
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fail_deprobe:
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unregister_trace_sched_wakeup(probe_sched_wakeup, NULL);
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return ret;
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}
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static void tracing_sched_unregister(void)
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{
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unregister_trace_sched_switch(probe_sched_switch, NULL);
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unregister_trace_sched_wakeup_new(probe_sched_wakeup, NULL);
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unregister_trace_sched_wakeup(probe_sched_wakeup, NULL);
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}
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static void tracing_start_sched_switch(int ops)
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{
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bool sched_register;
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mutex_lock(&sched_register_mutex);
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sched_register = (!sched_cmdline_ref && !sched_tgid_ref);
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switch (ops) {
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case RECORD_CMDLINE:
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sched_cmdline_ref++;
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break;
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case RECORD_TGID:
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sched_tgid_ref++;
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break;
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}
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if (sched_register && (sched_cmdline_ref || sched_tgid_ref))
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tracing_sched_register();
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mutex_unlock(&sched_register_mutex);
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}
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static void tracing_stop_sched_switch(int ops)
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{
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mutex_lock(&sched_register_mutex);
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switch (ops) {
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case RECORD_CMDLINE:
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sched_cmdline_ref--;
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break;
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case RECORD_TGID:
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sched_tgid_ref--;
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break;
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}
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if (!sched_cmdline_ref && !sched_tgid_ref)
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tracing_sched_unregister();
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mutex_unlock(&sched_register_mutex);
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}
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void tracing_start_cmdline_record(void)
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{
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tracing_start_sched_switch(RECORD_CMDLINE);
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}
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void tracing_stop_cmdline_record(void)
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{
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tracing_stop_sched_switch(RECORD_CMDLINE);
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}
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void tracing_start_tgid_record(void)
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{
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tracing_start_sched_switch(RECORD_TGID);
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}
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void tracing_stop_tgid_record(void)
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{
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tracing_stop_sched_switch(RECORD_TGID);
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}
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