[PATCH v3] vhost: fix use-after-free in fdset during shutdown

[Yehor Malikov <malikovyehor@gmail.com>]

From: Yehor Malikov <Yehor.Malikov@solidigm.com>

The fdset_event_dispatch thread runs in a loop checking the destroy
flag after each epoll_wait iteration. During process exit,
rte_eal_cleanup() frees hugepages memory while the fdset thread is
still running, causing use-after-free when accessing the fdset
structure.

Add fdset_deinit() function to properly stop the dispatch thread
before freeing resources:
- Set destroy flag to signal thread exit
- Wait for thread completion via rte_thread_join()
- Close epoll fd and free memory only after thread exits

Add RTE_FINI destructor to ensure fdset cleanup runs before EAL
cleanup frees hugepages.

Fixes: e68a6feaa3b3 ("vhost: improve fdset initialization")

Signed-off-by: Yehor Malikov <Yehor.Malikov@solidigm.com>
---
 .mailmap           |  1 +
 lib/vhost/fd_man.c | 33 +++++++++++++++++++++++++++++++++
 lib/vhost/fd_man.h |  1 +
 lib/vhost/socket.c |  8 ++++++++
 4 files changed, 43 insertions(+)

diff --git a/.mailmap b/.mailmap
index 34a99f93a1..6fb87ca810 100644
--- a/.mailmap
+++ b/.mailmap
@@ -1800,6 +1800,7 @@ Yaron Illouz <yaroni@radcom.com>
 Yaroslav Brustinov <ybrustin@cisco.com>
 Yash Sharma <ysharma@marvell.com>
 Yasufumi Ogawa <ogawa.yasufumi@lab.ntt.co.jp> <yasufum.o@gmail.com>
+Yehor Malikov <Yehor.Malikov@solidigm.com>
 Yelena Krivosheev <yelena@marvell.com>
 Yerden Zhumabekov <e_zhumabekov@sts.kz> <yerden.zhumabekov@sts.kz>
 Yevgeny Kliteynik <kliteyn@nvidia.com>
diff --git a/lib/vhost/fd_man.c b/lib/vhost/fd_man.c
index f9147edee7..4c759d44a4 100644
--- a/lib/vhost/fd_man.c
+++ b/lib/vhost/fd_man.c
@@ -149,6 +149,39 @@ fdset_init(const char *name)
 	return NULL;
 }
 
+void
+fdset_deinit(struct fdset *pfdset)
+{
+	unsigned int val;
+	int i;
+
+	if (pfdset == NULL)
+		return;
+
+	/* Signal the dispatch thread to stop */
+	pfdset->destroy = true;
+
+	/* Wait for the dispatch thread to exit */
+	if (rte_thread_join(pfdset->tid, &val) != 0)
+		VHOST_FDMAN_LOG(ERR, "Failed to join %s event dispatch thread", pfdset->name);
+
+	/* Close epoll fd */
+	close(pfdset->epfd);
+
+	/* Remove from global fdsets list */
+	pthread_mutex_lock(&fdsets_mutex);
+	for (i = 0; i < MAX_FDSETS; i++) {
+		if (fdsets[i] == pfdset) {
+			fdsets[i] = NULL;
+			break;
+		}
+	}
+	pthread_mutex_unlock(&fdsets_mutex);
+
+	/* Free the fdset */
+	rte_free(pfdset);
+}
+
 static int
 fdset_insert_entry(struct fdset *pfdset, int fd, fd_cb rcb, fd_cb wcb, void *dat)
 {
diff --git a/lib/vhost/fd_man.h b/lib/vhost/fd_man.h
index eadcc6fb42..c9e51badaa 100644
--- a/lib/vhost/fd_man.h
+++ b/lib/vhost/fd_man.h
@@ -15,6 +15,7 @@ struct fdset;
 typedef void (*fd_cb)(int fd, void *dat, int *close);
 
 struct fdset *fdset_init(const char *name);
+void fdset_deinit(struct fdset *pfdset);
 
 int fdset_add(struct fdset *pfdset, int fd,
 	fd_cb rcb, fd_cb wcb, void *dat);
diff --git a/lib/vhost/socket.c b/lib/vhost/socket.c
index 9b4f332f94..e953dd1849 100644
--- a/lib/vhost/socket.c
+++ b/lib/vhost/socket.c
@@ -1209,3 +1209,11 @@ rte_vhost_driver_start(const char *path)
 	else
 		return vhost_user_start_client(vsocket);
 }
+
+RTE_FINI(vhost_user_fdset_fini)
+{
+	if (vhost_user.fdset != NULL) {
+		fdset_deinit(vhost_user.fdset);
+		vhost_user.fdset = NULL;
+	}
+}
-- 
2.52.0