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authorOleg Nesterov <oleg@tv-sign.ru>2008-02-08 04:19:03 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-02-08 09:22:26 -0800
commit20686a309aa98c518adbbd9b57cdbb1804143deb (patch)
tree4aac811e67d777d3c0015ca51312aa93b4832d35
parent9cbab8100538efdd93aeae6fc37787d986f2f558 (diff)
ptrace_stop: fix racy nonstop_code setting
If the tracer is gone and we are not going to stop, ptrace_stop() sets ->exit_code = nostop_code. However, the tracer could actually clear the exit code before detaching. In that case get_signal_to_deliver() "resends" the signal which was cancelled by the debugger. For example, it is possible that a quick PTRACE_ATTACH + PTRACE_DETACH can leave the tracee in STOPPED state. Change the behaviour of ptrace_stop(). If the caller is ptrace notify(), we should always clear ->exit_code. If the caller is get_signal_to_deliver(), we should not touch it at all. To do so, change the nonstop_code parameter to "bool clear_code" and change the callers accordingly. Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Acked-by: Roland McGrath <roland@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--kernel/signal.c13
1 files changed, 7 insertions, 6 deletions
diff --git a/kernel/signal.c b/kernel/signal.c
index 678bffa437c..3fca710a5cd 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1591,10 +1591,10 @@ static int sigkill_pending(struct task_struct *tsk)
* That makes it a way to test a stopped process for
* being ptrace-stopped vs being job-control-stopped.
*
- * If we actually decide not to stop at all because the tracer is gone,
- * we leave nostop_code in current->exit_code.
+ * If we actually decide not to stop at all because the tracer
+ * is gone, we keep current->exit_code unless clear_code.
*/
-static void ptrace_stop(int exit_code, int nostop_code, siginfo_t *info)
+static void ptrace_stop(int exit_code, int clear_code, siginfo_t *info)
{
int killed = 0;
@@ -1641,7 +1641,8 @@ static void ptrace_stop(int exit_code, int nostop_code, siginfo_t *info)
* Don't drop the lock yet, another tracer may come.
*/
__set_current_state(TASK_RUNNING);
- current->exit_code = nostop_code;
+ if (clear_code)
+ current->exit_code = 0;
read_unlock(&tasklist_lock);
}
@@ -1675,7 +1676,7 @@ void ptrace_notify(int exit_code)
/* Let the debugger run. */
spin_lock_irq(&current->sighand->siglock);
- ptrace_stop(exit_code, 0, &info);
+ ptrace_stop(exit_code, 1, &info);
spin_unlock_irq(&current->sighand->siglock);
}
@@ -1782,7 +1783,7 @@ relock:
ptrace_signal_deliver(regs, cookie);
/* Let the debugger run. */
- ptrace_stop(signr, signr, info);
+ ptrace_stop(signr, 0, info);
/* We're back. Did the debugger cancel the sig? */
signr = current->exit_code;