musl - musl - an implementation of the standard library for Linux-based systems

musl - an implementation of the standard library for Linux-based systems

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author	Rich Felker <dalias@aerifal.cx>	2022年10月07日 18:51:36 -0400
committer	Rich Felker <dalias@aerifal.cx>	2022年10月19日 14:01:32 -0400
commit	d8f35e29d0e35a90f44c04de585470c211afddf9 (patch)
tree	a00ce19cc0fe9699ab2ad5baef543a2d621ad276 /src
parent	26c76a908b8613ea8a77d40f3bd51b02f984501c (diff)
download	musl-d8f35e29d0e35a90f44c04de585470c211afddf9.tar.gz

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

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.

Diffstat (limited to 'src')

-rw-r--r--

src/aio/aio.c

1 files changed, 6 insertions, 0 deletions

diff --git a/src/aio/aio.c b/src/aio/aio.c
index 82f8eccb..d7e063bf 100644
--- a/src/aio/aio.c
+++ b/src/aio/aio.c

@@ -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;

}

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