cxl: Fix afu_read() not doing finish_wait() on signal or non-blocking

If afu_read() returned due to a signal or the AFU file descriptor being
opened non-blocking it would not call finish_wait() before returning,
which could lead to a crash later when something else wakes up the wait
queue.

This patch restructures the wait logic to ensure that the cleanup is
done correctly.

Signed-off-by: Ian Munsie <imunsie@au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 15 insertions, 5 deletions

diff --git a/drivers/misc/cxl/file.c b/drivers/misc/cxl/file.c
index 847b7e646a7e..378b099e7c0b 100644
--- a/drivers/misc/cxl/file.c
+++ b/drivers/misc/cxl/file.c
@@ -273,6 +273,7 @@ static ssize_t afu_read(struct file *file, char __user *buf, size_t count,
         struct cxl_context *ctx = file->private_data;
         struct cxl_event event;
         unsigned long flags;
+        int rc;
         DEFINE_WAIT(wait);
 
         if (count < CXL_READ_MIN_SIZE)
@@ -285,13 +286,17 @@ static ssize_t afu_read(struct file *file, char __user *buf, size_t count,
                 if (ctx_event_pending(ctx))
                         break;
 
-                spin_unlock_irqrestore(&ctx->lock, flags);
-                if (file->f_flags & O_NONBLOCK)
-                        return -EAGAIN;
+                if (file->f_flags & O_NONBLOCK) {
+                        rc = -EAGAIN;
+                        goto out;
+                }
 
-                if (signal_pending(current))
-                        return -ERESTARTSYS;
+                if (signal_pending(current)) {
+                        rc = -ERESTARTSYS;
+                        goto out;
+                }
 
+                spin_unlock_irqrestore(&ctx->lock, flags);
                 pr_devel("afu_read going to sleep...\n");
                 schedule();
                 pr_devel("afu_read woken up\n");
@@ -336,6 +341,11 @@ static ssize_t afu_read(struct file *file, char __user *buf, size_t count,
         if (copy_to_user(buf, &event, event.header.size))
                 return -EFAULT;
         return event.header.size;
+
+out:
+        finish_wait(&ctx->wq, &wait);
+        spin_unlock_irqrestore(&ctx->lock, flags);
+        return rc;
 }
 
 static const struct file_operations afu_fops = {