USB: misc: yurex: fix race between read and write
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@suse.com> CC: stable@vger.kernel.org Link: https://lore.kernel.org/r/20240912132126.1034743-1-oneukum@suse.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -404,7 +404,6 @@ static ssize_t yurex_read(struct file *file, char __user *buffer, size_t count,
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struct usb_yurex *dev;
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int len = 0;
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char in_buffer[MAX_S64_STRLEN];
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unsigned long flags;
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dev = file->private_data;
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@ -419,9 +418,9 @@ static ssize_t yurex_read(struct file *file, char __user *buffer, size_t count,
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return -EIO;
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}
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spin_lock_irqsave(&dev->lock, flags);
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spin_lock_irq(&dev->lock);
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scnprintf(in_buffer, MAX_S64_STRLEN, "%lld\n", dev->bbu);
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spin_unlock_irqrestore(&dev->lock, flags);
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spin_unlock_irq(&dev->lock);
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mutex_unlock(&dev->io_mutex);
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return simple_read_from_buffer(buffer, count, ppos, in_buffer, len);
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@ -511,8 +510,11 @@ static ssize_t yurex_write(struct file *file, const char __user *user_buffer,
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__func__, retval);
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goto error;
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}
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if (set && timeout)
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if (set && timeout) {
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spin_lock_irq(&dev->lock);
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dev->bbu = c2;
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spin_unlock_irq(&dev->lock);
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}
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return timeout ? count : -EIO;
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error:
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