[RFC v2 01/10] pseries/papr-hvpipe: Fix race with interrupt handler

["Ritesh Harjani (IBM)" <ritesh.list@gmail.com>]

While executing ->ioctl handler or ->release handler, if an interrupt
fires on the same cpu, then we can enter into a deadlock.

This patch fixes both these handlers to take spin_lock_irq{save|restore}
versions of the lock to prevent this deadlock.

Cc: stable@vger.kernel.org
Fixes: 814ef095f12c9 ("powerpc/pseries: Add papr-hvpipe char driver for HVPIPE interfaces")
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
---
 arch/powerpc/platforms/pseries/papr-hvpipe.c | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/papr-hvpipe.c b/arch/powerpc/platforms/pseries/papr-hvpipe.c
index 14ae480d060a..c41d45e1986d 100644
--- a/arch/powerpc/platforms/pseries/papr-hvpipe.c
+++ b/arch/powerpc/platforms/pseries/papr-hvpipe.c
@@ -444,13 +444,14 @@ static int papr_hvpipe_handle_release(struct inode *inode,
 				struct file *file)
 {
 	struct hvpipe_source_info *src_info;
+	unsigned long flags;
 
 	/*
 	 * Hold the lock, remove source from src_list, reset the
 	 * hvpipe status and release the lock to prevent any race
 	 * with message event IRQ.
 	 */
-	spin_lock(&hvpipe_src_list_lock);
+	spin_lock_irqsave(&hvpipe_src_list_lock, flags);
 	src_info = file->private_data;
 	list_del(&src_info->list);
 	file->private_data = NULL;
@@ -461,10 +462,10 @@ static int papr_hvpipe_handle_release(struct inode *inode,
 	 */
 	if (src_info->hvpipe_status & HVPIPE_MSG_AVAILABLE) {
 		src_info->hvpipe_status = 0;
-		spin_unlock(&hvpipe_src_list_lock);
+		spin_unlock_irqrestore(&hvpipe_src_list_lock, flags);
 		hvpipe_rtas_recv_msg(NULL, 0);
 	} else
-		spin_unlock(&hvpipe_src_list_lock);
+		spin_unlock_irqrestore(&hvpipe_src_list_lock, flags);
 
 	kfree(src_info);
 	return 0;
@@ -480,20 +481,21 @@ static const struct file_operations papr_hvpipe_handle_ops = {
 static int papr_hvpipe_dev_create_handle(u32 srcID)
 {
 	struct hvpipe_source_info *src_info __free(kfree) = NULL;
+	unsigned long flags;
 
-	spin_lock(&hvpipe_src_list_lock);
+	spin_lock_irqsave(&hvpipe_src_list_lock, flags);
 	/*
 	 * Do not allow more than one process communicates with
 	 * each source.
 	 */
 	src_info = hvpipe_find_source(srcID);
 	if (src_info) {
-		spin_unlock(&hvpipe_src_list_lock);
+		spin_unlock_irqrestore(&hvpipe_src_list_lock, flags);
 		pr_err("pid(%d) is already using the source(%d)\n",
 				src_info->tsk->pid, srcID);
 		return -EALREADY;
 	}
-	spin_unlock(&hvpipe_src_list_lock);
+	spin_unlock_irqrestore(&hvpipe_src_list_lock, flags);
 
 	src_info = kzalloc_obj(*src_info, GFP_KERNEL_ACCOUNT);
 	if (!src_info)
@@ -510,18 +512,18 @@ static int papr_hvpipe_dev_create_handle(u32 srcID)
 		return fdf.err;
 
 	retain_and_null_ptr(src_info);
-	spin_lock(&hvpipe_src_list_lock);
+	spin_lock_irqsave(&hvpipe_src_list_lock, flags);
 	/*
 	 * If two processes are executing ioctl() for the same
 	 * source ID concurrently, prevent the second process to
 	 * acquire FD.
 	 */
 	if (hvpipe_find_source(srcID)) {
-		spin_unlock(&hvpipe_src_list_lock);
+		spin_unlock_irqrestore(&hvpipe_src_list_lock, flags);
 		return -EALREADY;
 	}
 	list_add(&src_info->list, &hvpipe_src_list);
-	spin_unlock(&hvpipe_src_list_lock);
+	spin_unlock_irqrestore(&hvpipe_src_list_lock, flags);
 	return fd_publish(fdf);
 }
 
-- 
2.39.5