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fix AS-safety of close when aio is in use and fd map is expanded

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the aio operations that lead to calling __aio_get_queue with the
possibility to expand the fd map are not AS-safe, but if they are
interrupted by a signal handler, the signal handler may call close,
which is required to be AS-safe. due to __aio_get_queue taking the
write lock without blocking signals, such a call to close from a
signal handler could deadlock.

change __aio_get_queue to block signals if it needs to obtain a write
lock, and restore when finished.
This commit is contained in:
Rich Felker 2022-10-07 18:51:36 -04:00
parent 26c76a908b
commit d8f35e29d0
1 changed files with 6 additions and 0 deletions
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6
src/aio/aio.c
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@ -82,6 +82,8 @@ static size_t io_thread_stack_size;
static struct aio_queue *__aio_get_queue(int fd, int need)
{
sigset_t allmask, origmask;
int masked = 0;
if (fd < 0) {
errno = EBADF;
return 0;
@ -93,6 +95,9 @@ static struct aio_queue *__aio_get_queue(int fd, int need)
if ((!map || !map[a] || !map[a][b] || !map[a][b][c] || !(q=map[a][b][c][d])) && need) {
pthread_rwlock_unlock(&maplock);
if (fcntl(fd, F_GETFD) < 0) return 0;
sigfillset(&allmask);
masked = 1;
pthread_sigmask(SIG_BLOCK, &allmask, &origmask);
pthread_rwlock_wrlock(&maplock);
if (!io_thread_stack_size) {
unsigned long val = __getauxval(AT_MINSIGSTKSZ);
@ -119,6 +124,7 @@ static struct aio_queue *__aio_get_queue(int fd, int need)
if (q) pthread_mutex_lock(&q->lock);
out:
pthread_rwlock_unlock(&maplock);
if (masked) pthread_sigmask(SIG_SETMASK, &origmask, 0);
return q;
}