[PATCH 5.10 254/518] USB: misc: yurex: fix race between read and write

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5.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Oliver Neukum <oneukum@xxxxxxxx>

[ Upstream commit 93907620b308609c72ba4b95b09a6aa2658bb553 ]

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 <oneukum@xxxxxxxx>
CC: stable@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/20240912132126.1034743-1-oneukum@xxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/usb/misc/yurex.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/misc/yurex.c b/drivers/usb/misc/yurex.c
index 62bd302e8bb71..494db0178c1e1 100644
--- a/drivers/usb/misc/yurex.c
+++ b/drivers/usb/misc/yurex.c
@@ -403,7 +403,6 @@ 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;
 
@@ -416,9 +415,9 @@ static ssize_t yurex_read(struct file *file, char __user *buffer, size_t count,
 	if (WARN_ON_ONCE(dev->bbu > S64_MAX || dev->bbu < S64_MIN))
 		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);
@@ -508,8 +507,11 @@ 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:
-- 
2.43.0







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