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| author | Thomas Gleixner <tglx@linutronix.de> | 2009-12-10 00:53:17 +0000 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2009-12-10 23:04:11 +0100 |
| commit | 14d8c9f3c09e7fd7b9af80904289fe204f5b93c6 (patch) | |
| tree | 1c373436517c5853aab0e99cce83364a21134d0e /kernel/signal.c | |
| parent | ea5b41f9d595be354f7a50e56b28c2d72e6e88a5 (diff) | |
| download | lwn-14d8c9f3c09e7fd7b9af80904289fe204f5b93c6.tar.gz lwn-14d8c9f3c09e7fd7b9af80904289fe204f5b93c6.zip | |
signal: Fix racy access to __task_cred in kill_pid_info_as_uid()
kill_pid_info_as_uid() accesses __task_cred() without being in a RCU
read side critical section. tasklist_lock is not protecting that when
CONFIG_TREE_PREEMPT_RCU=y.
Convert the whole tasklist_lock section to rcu and use
lock_task_sighand to prevent the exit race.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
LKML-Reference: <20091210004703.232302055@linutronix.de>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Diffstat (limited to 'kernel/signal.c')
| -rw-r--r-- | kernel/signal.c | 17 |
1 files changed, 10 insertions, 7 deletions
diff --git a/kernel/signal.c b/kernel/signal.c index 6b982f2cf524..73316568a69c 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -1175,11 +1175,12 @@ int kill_pid_info_as_uid(int sig, struct siginfo *info, struct pid *pid, int ret = -EINVAL; struct task_struct *p; const struct cred *pcred; + unsigned long flags; if (!valid_signal(sig)) return ret; - read_lock(&tasklist_lock); + rcu_read_lock(); p = pid_task(pid, PIDTYPE_PID); if (!p) { ret = -ESRCH; @@ -1196,14 +1197,16 @@ int kill_pid_info_as_uid(int sig, struct siginfo *info, struct pid *pid, ret = security_task_kill(p, info, sig, secid); if (ret) goto out_unlock; - if (sig && p->sighand) { - unsigned long flags; - spin_lock_irqsave(&p->sighand->siglock, flags); - ret = __send_signal(sig, info, p, 1, 0); - spin_unlock_irqrestore(&p->sighand->siglock, flags); + + if (sig) { + if (lock_task_sighand(p, &flags)) { + ret = __send_signal(sig, info, p, 1, 0); + unlock_task_sighand(p, &flags); + } else + ret = -ESRCH; } out_unlock: - read_unlock(&tasklist_lock); + rcu_read_unlock(); return ret; } EXPORT_SYMBOL_GPL(kill_pid_info_as_uid); |