USB: misc: yurex: fix race between read and write

Commit Message

Oliver Neukum Sept. 12, 2024, 1:21 p.m. UTC

The write code path touches the bbu member in a non atomic manner
without taking the spinlock. Fix it.

The bug is as old as the driver.

Signed-off-by: Oliver Neukum <[e-mail]>
CC: [e-mail]
---
 drivers/usb/misc/yurex.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

Patch

diff --git a/drivers/usb/misc/yurex.c b/drivers/usb/misc/yurex.c
index 4745a320eae4..4a9859e03f6b 100644
--- a/drivers/usb/misc/yurex.c
+++ b/drivers/usb/misc/yurex.c
@@ -404,7 +404,6 @@  static ssize_t yurex_read(struct file *file, char __user *buffer, size_t count,
 	struct usb_yurex *dev;
 	int len = 0;
 	char in_buffer[MAX_S64_STRLEN];
-	unsigned long flags;
 
 	dev = file->private_data;
 
@@ -419,9 +418,9 @@  static ssize_t yurex_read(struct file *file, char __user *buffer, size_t count,
 		return -EIO;
 	}
 
-	spin_lock_irqsave(&dev->lock, flags);
+	spin_lock_irq(&dev->lock);
 	scnprintf(in_buffer, MAX_S64_STRLEN, "%lld\n", dev->bbu);
-	spin_unlock_irqrestore(&dev->lock, flags);
+	spin_unlock_irq(&dev->lock);
 	mutex_unlock(&dev->io_mutex);
 
 	return simple_read_from_buffer(buffer, count, ppos, in_buffer, len);
@@ -511,8 +510,11 @@  static ssize_t yurex_write(struct file *file, const char __user *user_buffer,
 			__func__, retval);
 		goto error;
 	}
-	if (set && timeout)
+	if (set && timeout) {
+		spin_lock_irq(&dev->lock);
 		dev->bbu = c2;
+		spin_unlock_irq(&dev->lock);
+	}
 	return timeout ? count : -EIO;
 
 error: