diff options
| author | Oleg Nesterov <oleg@tv-sign.ru> | 2008-02-08 04:19:18 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2008-02-08 09:22:28 -0800 |
| commit | d36174bc2bce0372693a9cfbdef8b2689c9982cb (patch) | |
| tree | cdb327c68844f105a8ac8b732e862f24edc35f24 | |
| parent | f374ada53bd1ca7c16d7607369fccc6769704956 (diff) | |
uglify kill_pid_info() to fix kill() vs exec() race
kill_pid_info()->pid_task() could be the old leader of the execing process.
In that case it is possible that the leader will be released before we take
siglock. This means that kill_pid_info() (and thus sys_kill()) can return a
false -ESRCH.
Change the code to retry when lock_task_sighand() fails. The endless loop is
not possible, __exit_signal() both clears ->sighand and does detach_pid().
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Davide Libenzi <davidel@xmailserver.org>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: 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.c | 15 |
1 files changed, 12 insertions, 3 deletions
diff --git a/kernel/signal.c b/kernel/signal.c index 3d3adb94561d..b0b43a4ad8dd 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -1050,17 +1050,26 @@ int kill_pgrp_info(int sig, struct siginfo *info, struct pid *pgrp) int kill_pid_info(int sig, struct siginfo *info, struct pid *pid) { - int error; + int error = -ESRCH; struct task_struct *p; rcu_read_lock(); if (unlikely(sig_needs_tasklist(sig))) read_lock(&tasklist_lock); +retry: p = pid_task(pid, PIDTYPE_PID); - error = -ESRCH; - if (p) + if (p) { error = group_send_sig_info(sig, info, p); + if (unlikely(error == -ESRCH)) + /* + * The task was unhashed in between, try again. + * If it is dead, pid_task() will return NULL, + * if we race with de_thread() it will find the + * new leader. + */ + goto retry; + } if (unlikely(sig_needs_tasklist(sig))) read_unlock(&tasklist_lock); |