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

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[ Upstream commit 93907620b3 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Oliver Neukum 2024-09-12 15:21:22 +02:00 committed by Greg Kroah-Hartman
parent eff6dde4c3
commit 225643310d
1 changed files with 6 additions and 4 deletions
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10
drivers/usb/misc/yurex.c
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@ -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;
@ -417,9 +416,9 @@ 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);
@ -509,8 +508,11 @@ 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: