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Commit 4af4206b authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Steven Rostedt
Browse files

tracing: Fix syscall_*regfunc() vs copy_process() race 

syscall_regfunc() and syscall_unregfunc() should set/clear
TIF_SYSCALL_TRACEPOINT system-wide, but do_each_thread() can race
with copy_process() and miss the new child which was not added to
the process/thread lists yet.

Change copy_process() to update the child's TIF_SYSCALL_TRACEPOINT
under tasklist.

Link: http://lkml.kernel.org/p/20140413185854.GB20668@redhat.com



Cc: stable@vger.kernel.org # 2.6.33
Fixes: a871bd33 "tracing: Add syscall tracepoints"
Acked-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
Acked-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 7171511e

include/trace/syscall.h

+15 −0
Original line number Diff line number Diff line
@@ -4,6 +4,7 @@ 
#include <linux/tracepoint.h>

#include <linux/unistd.h>

#include <linux/ftrace_event.h>

#include <linux/thread_info.h>



#include <asm/ptrace.h>
@@ -32,4 +33,18 @@ struct syscall_metadata { 
	struct ftrace_event_call *exit_event;

};



#if defined(CONFIG_TRACEPOINTS) && defined(CONFIG_HAVE_SYSCALL_TRACEPOINTS)

static inline void syscall_tracepoint_update(struct task_struct *p)

{

	if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))

		set_tsk_thread_flag(p, TIF_SYSCALL_TRACEPOINT);

	else

		clear_tsk_thread_flag(p, TIF_SYSCALL_TRACEPOINT);

}

#else

static inline void syscall_tracepoint_update(struct task_struct *p)

{

}

#endif



#endif /* _TRACE_SYSCALL_H */

kernel/fork.c

+2 −0
Original line number Diff line number Diff line
@@ -1487,7 +1487,9 @@ static struct task_struct *copy_process(unsigned long clone_flags, 


	total_forks++;

	spin_unlock(&current->sighand->siglock);

	syscall_tracepoint_update(p);

	write_unlock_irq(&tasklist_lock);



	proc_fork_connector(p);

	cgroup_post_fork(p);

	if (clone_flags & CLONE_THREAD)