VisionFive2 Linux kernel

StarFive Tech Linux Kernel for VisionFive (JH7110) boards (mirror)

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author: Siddh Raman Pant <code@siddh.me> 2023-06-05 20:06:16 +0530 committer: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 2023-07-19 16:36:53 +0200 commit: bec85c4df15d29664245f7b7e9cd7dc926d6e699 parent: 4514847aee18d9391a0cf3aad75d3567c72795a4
Commit Summary:
watch_queue: prevent dangling pipe pointer
Diffstat:
2 files changed, 7 insertions, 8 deletions
diff --git a/include/linux/watch_queue.h b/include/linux/watch_queue.h
index fc6bba20273b..45cd42f55d49 100644
--- a/include/linux/watch_queue.h
+++ b/include/linux/watch_queue.h
@@ -38,7 +38,7 @@ struct watch_filter {
 struct watch_queue {
 	struct rcu_head		rcu;
 	struct watch_filter __rcu *filter;
-	struct pipe_inode_info	*pipe;		/* The pipe we're using as a buffer */
+	struct pipe_inode_info	*pipe;		/* Pipe we use as a buffer, NULL if queue closed */
 	struct hlist_head	watches;	/* Contributory watches */
 	struct page		**notes;	/* Preallocated notifications */
 	unsigned long		*notes_bitmap;	/* Allocation bitmap for notes */
@@ -46,7 +46,6 @@ struct watch_queue {
 	spinlock_t		lock;
 	unsigned int		nr_notes;	/* Number of notes */
 	unsigned int		nr_pages;	/* Number of pages in notes[] */
-	bool			defunct;	/* T when queues closed */
 };
 
 /*
diff --git a/kernel/watch_queue.c b/kernel/watch_queue.c
index e91cb4c2833f..d0b6b390ee42 100644
--- a/kernel/watch_queue.c
+++ b/kernel/watch_queue.c
@@ -42,7 +42,7 @@ MODULE_AUTHOR("Red Hat, Inc.");
 static inline bool lock_wqueue(struct watch_queue *wqueue)
 {
 	spin_lock_bh(&wqueue->lock);
-	if (unlikely(wqueue->defunct)) {
+	if (unlikely(!wqueue->pipe)) {
 		spin_unlock_bh(&wqueue->lock);
 		return false;
 	}
@@ -104,9 +104,6 @@ static bool post_one_notification(struct watch_queue *wqueue,
 	unsigned int head, tail, mask, note, offset, len;
 	bool done = false;
 
-	if (!pipe)
-		return false;
-
 	spin_lock_irq(&pipe->rd_wait.lock);
 
 	mask = pipe->ring_size - 1;
@@ -603,8 +600,11 @@ void watch_queue_clear(struct watch_queue *wqueue)
 	rcu_read_lock();
 	spin_lock_bh(&wqueue->lock);
 
-	/* Prevent new notifications from being stored. */
-	wqueue->defunct = true;
+	/*
+	 * This pipe can be freed by callers like free_pipe_info().
+	 * Removing this reference also prevents new notifications.
+	 */
+	wqueue->pipe = NULL;
 
 	while (!hlist_empty(&wqueue->watches)) {
 		watch = hlist_entry(wqueue->watches.first, struct watch, queue_node);