gpio: cdev: fix kernel stack leak to user-space in error path

Overview

In the Linux kernel, the following vulnerability has been resolved:

gpio: cdev: fix kernel stack leak to user-space in error path

If we fail to acquire the GPIO chip guard in gpio_desc_to_lineinfo(), we return immediately before zeroing the info struct we'll end up passing to the user-space later in lineinfo_get_v1(). This may leak the kernel stack contents. Make gpio_desc_to_lineinfo() return int so that the -ENODEV returned on failure to acquire the guard can be propagated to the callers.

While not strictly necessary: move the memset() before trying to acquire the SRCU read lock too for good measure.

Affected

• Linux >= d83cee3d2bb131c7fca7e19f1e33dc7530fd7083 < 8460ee5216ab9a38263b01dca4b0a27e083f70f3
• Linux >= d83cee3d2bb131c7fca7e19f1e33dc7530fd7083 < cf3d043582e106a0e57002bec8a6de8929ba3e1c
• Linux >= d83cee3d2bb131c7fca7e19f1e33dc7530fd7083 < 60a466f231905cd96ae6f0f3c44a710c97873dac
• Linux >= d83cee3d2bb131c7fca7e19f1e33dc7530fd7083 < 1feb5d39b05afd902ed9fc902ec5b15be03a4bdb
• Linux 6.9

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.