Merge tag 'erofs-for-5.18-rc4-fixes' of git://git.kernel.org/pub/scm/…

…linux/kernel/git/xiang/erofs

Pull erofs fixes from Gao Xiang:
 "One patch to fix a use-after-free race related to the on-stack
  z_erofs_decompressqueue, which happens very rarely but needs to be
  fixed properly soon.

  The other patch fixes some sysfs Sphinx warnings"

* tag 'erofs-for-5.18-rc4-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs:
  Documentation/ABI: sysfs-fs-erofs: Fix Sphinx errors
  erofs: fix use-after-free of on-stack io[]

Documentation/ABI/testing/sysfs-fs-erofs

@@ -9,8 +9,9 @@ Description:	Shows all enabled kernel features.
 What:		/sys/fs/erofs/<disk>/sync_decompress
 Date:		November 2021
 Contact:	"Huang Jianan" <huangjianan@oppo.com>
-Description:	Control strategy of sync decompression
+Description:	Control strategy of sync decompression:
+
 		- 0 (default, auto): enable for readpage, and enable for
-				     readahead on atomic contexts only,
+		  readahead on atomic contexts only.
 		- 1 (force on): enable for readpage and readahead.
 		- 2 (force off): disable for all situations.

fs/erofs/zdata.c

@@ -1066,12 +1066,9 @@ static void z_erofs_decompress_kickoff(struct z_erofs_decompressqueue *io,
 
 	/* wake up the caller thread for sync decompression */
 	if (sync) {
-		unsigned long flags;
-
-		spin_lock_irqsave(&io->u.wait.lock, flags);
 		if (!atomic_add_return(bios, &io->pending_bios))
-			wake_up_locked(&io->u.wait);
-		spin_unlock_irqrestore(&io->u.wait.lock, flags);
+			complete(&io->u.done);
+
 		return;
 	}
 
@@ -1217,7 +1214,7 @@ jobqueue_init(struct super_block *sb,
 	} else {
 fg_out:
 		q = fgq;
-		init_waitqueue_head(&fgq->u.wait);
+		init_completion(&fgq->u.done);
 		atomic_set(&fgq->pending_bios, 0);
 	}
 	q->sb = sb;
@@ -1419,8 +1416,7 @@ static void z_erofs_runqueue(struct super_block *sb,
 		return;
 
 	/* wait until all bios are completed */
-	io_wait_event(io[JQ_SUBMIT].u.wait,
-		      !atomic_read(&io[JQ_SUBMIT].pending_bios));
+	wait_for_completion_io(&io[JQ_SUBMIT].u.done);
 
 	/* handle synchronous decompress queue in the caller context */
 	z_erofs_decompress_queue(&io[JQ_SUBMIT], pagepool);

fs/erofs/zdata.h

@@ -97,7 +97,7 @@ struct z_erofs_decompressqueue {
 	z_erofs_next_pcluster_t head;
 
 	union {
-		wait_queue_head_t wait;
+		struct completion done;
 		struct work_struct work;
 	} u;
 };