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authorOleg Nesterov <oleg@tv-sign.ru>2005-09-06 18:17:42 -0400
committerLinus Torvalds <torvalds@g5.osdl.org>2005-09-07 19:57:33 -0400
commite752dd6cc66a3e6a11396928998baf390cc00420 (patch)
treeb24b388d80acec6527e66b07f0d308d48319c476 /kernel
parenta97c9bf33f4612e2aed6f000f6b1d268b6814f3c (diff)
[PATCH] fix send_sigqueue() vs thread exit race
posix_timer_event() first checks that the thread (SIGEV_THREAD_ID case) does not have PF_EXITING flag, then it calls send_sigqueue() which locks task list. But if the thread exits in between the kernel will oops (->sighand == NULL after __exit_sighand). This patch moves the PF_EXITING check into the send_sigqueue(), it must be done atomically under tasklist_lock. When send_sigqueue() detects exiting thread it returns -1. In that case posix_timer_event will send the signal to thread group. Also, this patch fixes task_struct use-after-free in posix_timer_event. Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/posix-timers.c28
-rw-r--r--kernel/signal.c22
2 files changed, 27 insertions, 23 deletions
diff --git a/kernel/posix-timers.c b/kernel/posix-timers.c
index 38798a2ff994..b7b532acd9fc 100644
--- a/kernel/posix-timers.c
+++ b/kernel/posix-timers.c
@@ -427,21 +427,23 @@ int posix_timer_event(struct k_itimer *timr,int si_private)
427 timr->sigq->info.si_code = SI_TIMER; 427 timr->sigq->info.si_code = SI_TIMER;
428 timr->sigq->info.si_tid = timr->it_id; 428 timr->sigq->info.si_tid = timr->it_id;
429 timr->sigq->info.si_value = timr->it_sigev_value; 429 timr->sigq->info.si_value = timr->it_sigev_value;
430
430 if (timr->it_sigev_notify & SIGEV_THREAD_ID) { 431 if (timr->it_sigev_notify & SIGEV_THREAD_ID) {
431 if (unlikely(timr->it_process->flags & PF_EXITING)) { 432 struct task_struct *leader;
432 timr->it_sigev_notify = SIGEV_SIGNAL; 433 int ret = send_sigqueue(timr->it_sigev_signo, timr->sigq,
433 put_task_struct(timr->it_process); 434 timr->it_process);
434 timr->it_process = timr->it_process->group_leader; 435
435 goto group; 436 if (likely(ret >= 0))
436 } 437 return ret;
437 return send_sigqueue(timr->it_sigev_signo, timr->sigq, 438
438 timr->it_process); 439 timr->it_sigev_notify = SIGEV_SIGNAL;
439 } 440 leader = timr->it_process->group_leader;
440 else { 441 put_task_struct(timr->it_process);
441 group: 442 timr->it_process = leader;
442 return send_group_sigqueue(timr->it_sigev_signo, timr->sigq,
443 timr->it_process);
444 } 443 }
444
445 return send_group_sigqueue(timr->it_sigev_signo, timr->sigq,
446 timr->it_process);
445} 447}
446EXPORT_SYMBOL_GPL(posix_timer_event); 448EXPORT_SYMBOL_GPL(posix_timer_event);
447 449
diff --git a/kernel/signal.c b/kernel/signal.c
index 56e33df2b67f..4980a073237f 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1366,16 +1366,16 @@ send_sigqueue(int sig, struct sigqueue *q, struct task_struct *p)
1366 unsigned long flags; 1366 unsigned long flags;
1367 int ret = 0; 1367 int ret = 0;
1368 1368
1369 /*
1370 * We need the tasklist lock even for the specific
1371 * thread case (when we don't need to follow the group
1372 * lists) in order to avoid races with "p->sighand"
1373 * going away or changing from under us.
1374 */
1375 BUG_ON(!(q->flags & SIGQUEUE_PREALLOC)); 1369 BUG_ON(!(q->flags & SIGQUEUE_PREALLOC));
1376 read_lock(&tasklist_lock); 1370 read_lock(&tasklist_lock);
1371
1372 if (unlikely(p->flags & PF_EXITING)) {
1373 ret = -1;
1374 goto out_err;
1375 }
1376
1377 spin_lock_irqsave(&p->sighand->siglock, flags); 1377 spin_lock_irqsave(&p->sighand->siglock, flags);
1378 1378
1379 if (unlikely(!list_empty(&q->list))) { 1379 if (unlikely(!list_empty(&q->list))) {
1380 /* 1380 /*
1381 * If an SI_TIMER entry is already queue just increment 1381 * If an SI_TIMER entry is already queue just increment
@@ -1385,7 +1385,7 @@ send_sigqueue(int sig, struct sigqueue *q, struct task_struct *p)
1385 BUG(); 1385 BUG();
1386 q->info.si_overrun++; 1386 q->info.si_overrun++;
1387 goto out; 1387 goto out;
1388 } 1388 }
1389 /* Short-circuit ignored signals. */ 1389 /* Short-circuit ignored signals. */
1390 if (sig_ignored(p, sig)) { 1390 if (sig_ignored(p, sig)) {
1391 ret = 1; 1391 ret = 1;
@@ -1400,8 +1400,10 @@ send_sigqueue(int sig, struct sigqueue *q, struct task_struct *p)
1400 1400
1401out: 1401out:
1402 spin_unlock_irqrestore(&p->sighand->siglock, flags); 1402 spin_unlock_irqrestore(&p->sighand->siglock, flags);
1403out_err:
1403 read_unlock(&tasklist_lock); 1404 read_unlock(&tasklist_lock);
1404 return(ret); 1405
1406 return ret;
1405} 1407}
1406 1408
1407int 1409int