diff options
author | Oleg Nesterov <oleg@tv-sign.ru> | 2008-02-08 12:19:03 (GMT) |
---|---|---|
committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2008-02-08 17:22:26 (GMT) |
commit | 20686a309aa98c518adbbd9b57cdbb1804143deb (patch) | |
tree | 4aac811e67d777d3c0015ca51312aa93b4832d35 /kernel | |
parent | 9cbab8100538efdd93aeae6fc37787d986f2f558 (diff) | |
download | linux-fsl-qoriq-20686a309aa98c518adbbd9b57cdbb1804143deb.tar.xz |
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>
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/signal.c | 13 |
1 files changed, 7 insertions, 6 deletions
diff --git a/kernel/signal.c b/kernel/signal.c index 678bffa..3fca710 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(¤t->sighand->siglock); - ptrace_stop(exit_code, 0, &info); + ptrace_stop(exit_code, 1, &info); spin_unlock_irq(¤t->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; |