From d184d6eb1dc3c9869e25a8e422be5c55ab0db4ac Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Fri, 8 Jul 2011 19:14:17 +0200 Subject: ptrace: dont send SIGSTOP on auto-attach if PT_SEIZED The fake SIGSTOP during attach has numerous problems. PTRACE_SEIZE is already fine, but we have basically the same problems is SIGSTOP is sent on auto-attach, the tracer can't know if this signal signal should be cancelled or not. Change ptrace_event() to set JOBCTL_TRAP_STOP if the new child is PT_SEIZED, this triggers the PTRACE_EVENT_STOP report. Thereafter a PT_SEIZED task can never report the bogus SIGSTOP. Test-case: #define PTRACE_SEIZE 0x4206 #define PTRACE_SEIZE_DEVEL 0x80000000 #define PTRACE_EVENT_STOP 7 #define WEVENT(s) ((s & 0xFF0000) >> 16) int main(void) { int child, grand_child, status; long message; child = fork(); if (!child) { kill(getpid(), SIGSTOP); fork(); assert(0); return 0x23; } assert(ptrace(PTRACE_SEIZE, child, 0,PTRACE_SEIZE_DEVEL) == 0); assert(wait(&status) == child); assert(WIFSTOPPED(status) && WSTOPSIG(status) == SIGSTOP); assert(ptrace(PTRACE_SETOPTIONS, child, 0, PTRACE_O_TRACEFORK) == 0); assert(ptrace(PTRACE_CONT, child, 0,0) == 0); assert(waitpid(child, &status, 0) == child); assert(WIFSTOPPED(status) && WSTOPSIG(status) == SIGTRAP); assert(WEVENT(status) == PTRACE_EVENT_FORK); assert(ptrace(PTRACE_GETEVENTMSG, child, 0, &message) == 0); grand_child = message; assert(waitpid(grand_child, &status, 0) == grand_child); assert(WIFSTOPPED(status) && WSTOPSIG(status) == SIGTRAP); assert(WEVENT(status) == PTRACE_EVENT_STOP); kill(child, SIGKILL); kill(grand_child, SIGKILL); return 0; } Signed-off-by: Oleg Nesterov Acked-by: Tejun Heo --- include/linux/ptrace.h | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) (limited to 'include/linux/ptrace.h') diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h index 9b5d2c901d06..800f113bea66 100644 --- a/include/linux/ptrace.h +++ b/include/linux/ptrace.h @@ -228,7 +228,11 @@ static inline void ptrace_init_task(struct task_struct *child, bool ptrace) child->ptrace = current->ptrace; __ptrace_link(child, current->parent); - sigaddset(&child->pending.signal, SIGSTOP); + if (child->ptrace & PT_SEIZED) + task_set_jobctl_pending(child, JOBCTL_TRAP_STOP); + else + sigaddset(&child->pending.signal, SIGSTOP); + set_tsk_thread_flag(child, TIF_SIGPENDING); } } -- cgit v1.2.3-59-g8ed1b