[PATCH 3.2 092/125] tracing: Fix syscall_*regfunc() vs copy_process() race

From: Ben Hutchings
Date: Tue Jul 08 2014 - 15:33:44 EST

3.2.61-rc1 review patch. If anyone has any objections, please let me know.


From: Oleg Nesterov <oleg@xxxxxxxxxx>

commit 4af4206be2bd1933cae20c2b6fb2058dbc887f7c 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@xxxxxxxxxx

Fixes: a871bd33a6c0 "tracing: Add syscall tracepoints"
Acked-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Acked-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
include/trace/syscall.h | 15 +++++++++++++++
kernel/fork.c | 2 ++
2 files changed, 17 insertions(+)

--- a/include/trace/syscall.h
+++ b/include/trace/syscall.h
@@ -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>

@@ -54,4 +55,18 @@ int perf_sysexit_enable(struct ftrace_ev
void perf_sysexit_disable(struct ftrace_event_call *call);

+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);
+static inline void syscall_tracepoint_update(struct task_struct *p)
#endif /* _TRACE_SYSCALL_H */
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1370,7 +1370,9 @@ static struct task_struct *copy_process(

+ syscall_tracepoint_update(p);
if (clone_flags & CLONE_THREAD)

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