Messages in this thread Patch in this message | | | Date | Tue, 2 Nov 2010 15:58:21 +0200 | From | Sergey Senozhatsky <> | Subject | [PATCH] posix-cpu-timers: rcu_read_lock/unlock protect find_task_by_vpid call |
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Commit 4221a9918e38b7494cee341dda7b7b4bb8c04bde "Add RCU check for find_task_by_vpid()" introduced rcu_lockdep_assert to find_task_by_pid_ns. Add rcu_read_lock/rcu_read_unlock to call find_task_by_vpid.
Tetsuo Handa wrote:
Quoting from one of posts in that thead http://kerneltrap.org/mailarchive/linux-kernel/2010/2/8/4536388
| Usually tasklist gives enough protection, but if copy_process() fails | it calls free_pid() lockless and does call_rcu(delayed_put_pid(). | This means, without rcu lock find_pid_ns() can't scan the hash table | safely.
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
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diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c index 6842eeb..855bc53 100644 --- a/kernel/posix-cpu-timers.c +++ b/kernel/posix-cpu-timers.c @@ -38,11 +38,13 @@ static int check_clock(const clockid_t which_clock) return 0; read_lock(&tasklist_lock); + rcu_read_lock(); p = find_task_by_vpid(pid); if (!p || !(CPUCLOCK_PERTHREAD(which_clock) ? same_thread_group(p, current) : thread_group_leader(p))) { error = -EINVAL; } + rcu_read_unlock(); read_unlock(&tasklist_lock); return error; @@ -395,17 +397,21 @@ int posix_cpu_timer_create(struct k_itimer *new_timer) if (pid == 0) { p = current; } else { + rcu_read_lock(); p = find_task_by_vpid(pid); if (p && !same_thread_group(p, current)) p = NULL; + rcu_read_unlock(); } } else { if (pid == 0) { p = current->group_leader; } else { + rcu_read_lock(); p = find_task_by_vpid(pid); if (p && !thread_group_leader(p)) p = NULL; + rcu_read_unlock(); } } new_timer->it.cpu.task = p;
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