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

commit 4af4206be2 upstream.

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

Fixes: a871bd33a6 "tracing: Add syscall tracepoints"
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Oleg Nesterov 2014-04-13 20:58:54 +02:00 committed by Greg Kroah-Hartman
parent d2b095b62f
commit 6a2e92a4a6
2 changed files with 17 additions and 0 deletions
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15
include/trace/syscall.h
View File

@ -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 */

2
kernel/fork.c
View File

@ -1484,7 +1484,9 @@ 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)