The patch titled
ptrace-simplify-ptrace_exit-ignoring_children-pathpatch fix
has been added to the -mm tree. Its filename is
ptrace-simplify-ptrace_exit-ignoring_children-pathpatch-fix.patch
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------------------------------------------------------
Subject: ptrace-simplify-ptrace_exit-ignoring_children-pathpatch fix
From: Oleg Nesterov <oleg@xxxxxxxxxx>
Somehow I didn't even try to think about false _negative_, and it is
possible without ->siglock.
If we race with sigaction() which changes ->action[SIGCHLD]
from: { .sa_handler = SIG_IGN, .sa_flags = 0 }
to: { .sa_handler = handler, .sa_flags = SA_NOCLDWAIT }
we can read the stores out of order, and ignoring_children() may
return the wrong "false". Nothing really bad can happen, and the
race is mostly theoretical, but still this is not right.
[PATCH 2/4] ptrace: simplify ptrace_exit()->ignoring_children() path
In order to avoid the unnecessary ignoring_children() calls, ptrace_exit()
uses "int ign" to cache the returned value.
This makes sense because ptrace_exit() works with the list of tracees, but
the next patche changes this code to work with individual threads.
Remove this optimization, I don't think it is common to exit with a lot of
attached EXIT_ZOMBIE tracees. And this makes the code a bit simpler.
Also remove _irqsave/_irqrestore, this code always runs with irqs disabled.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Jerome Marchand <jmarchan@xxxxxxxxxx>
Cc: Roland McGrath <roland@xxxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/exit.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff -puN kernel/exit.c~ptrace-simplify-ptrace_exit-ignoring_children-pathpatch-fix kernel/exit.c
--- a/kernel/exit.c~ptrace-simplify-ptrace_exit-ignoring_children-pathpatch-fix
+++ a/kernel/exit.c
@@ -729,12 +729,16 @@ static void exit_mm(struct task_struct *
}
/*
- * Return nonzero if childs should reap themselves.
+ * Called with irqs disabled, returns true if childs should reap themselves.
*/
static int ignoring_children(struct sighand_struct *sigh)
{
- return sigh->action[SIGCHLD-1].sa.sa_handler == SIG_IGN ||
- sigh->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT;
+ int ret;
+ spin_lock(&sigh->siglock);
+ ret = (sigh->action[SIGCHLD-1].sa.sa_handler == SIG_IGN) ||
+ (sigh->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT);
+ spin_unlock(&sigh->siglock);
+ return ret;
}
/*
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
origin.patch
wait-prevent-exclusive-waiter-starvation.patch
linux-next.patch
pipe_rdwr_fasync-fix-the-error-handling-to-prevent-the-leak-crash.patch
get_mm_hiwater_xxx-trivial-s-define-inline.patch
getrusage-fill-ru_maxrss-value.patch
ptrace-kill-__ptrace_detach-fix-exit_state-check.patch
ptrace-simplify-ptrace_exit-ignoring_children-path.patch
ptrace-simplify-ptrace_exit-ignoring_children-pathpatch-fix.patch
ptrace-reintroduce-__ptrace_detach-as-a-callee-of-ptrace_exit.patch
ptrace-fix-possible-zombie-leak-on-ptrace_detach.patch
reparent_thread-dont-call-kill_orphaned_pgrp-if-task_detached.patch
reparent_thread-fix-the-is-it-traced-check.patch
reparent_thread-fix-a-zombie-leak-if-sbin-init-ignores-sigchld.patch
forget_original_parent-cleanup-ptrace-pathes.patch
kthread-dont-looking-for-a-task-in-create_kthread-2.patch
pids-document-task_pgrp-task_session-is-not-safe-without-tasklist-rcu.patch
pids-document-task_pgrp-task_session-is-not-safe-without-tasklist-rcu-fix.patch
pids-improve-get_task_pid-to-fix-the-unsafe-sys_wait4-task_pgrp.patch
pids-refactor-vnr-nr_ns-helpers-to-make-them-safe.patch
pids-kill-now-unused-signal_struct-__pgrp-__session-and-friends.patch
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