usb: storage: sierra_ms: reject short SWoC info transfers

Overview

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

usb: storage: sierra_ms: reject short SWoC info transfers

sierra_get_swoc_info() requests sizeof(struct swoc_info) (60) bytes from the device via usb_control_msg(), but its callers only treat a negative return value as failure. A device that answers the vendor-specific GetSwocInfo request with a short IN transfer is therefore accepted, leaving the tail of the freshly allocated (kmalloc(), non-zeroing) swoc_info buffer uninitialized.

truinst_show() subsequently prints swocInfo->rev, swocInfo->LinuxSKU and swocInfo->LinuxVer from that buffer into the world-readable (0444) "truinst" sysfs attribute. An emulated/malicious USB device (VID 0x1199, PID 0x0fff) can exploit this to disclose up to 5 bytes of stale kernel heap memory (kmalloc-64) to unprivileged userspace, once per sysfs read, indefinitely. On kernels built without init_on_alloc this leaks recently freed heap contents.

Only accept the transfer when the full structure was received. sierra_ms_init() already retries failed queries, so well-behaved devices are unaffected.

Affected

• Linux >= 32fe5e393455d87db4988af03915634304870fb4 < c85e8331d298b8f1dee8fe63718e76435cec7133
• Linux >= 32fe5e393455d87db4988af03915634304870fb4 < e2d62928f2666a2964a23b1d39e6e762f0628d7b
• Linux >= 32fe5e393455d87db4988af03915634304870fb4 < db9d3be156baca6ef80ae5d93acfeb85c61a74dd
• Linux >= 32fe5e393455d87db4988af03915634304870fb4 < 8a0200d14acd9db388b85cd016e68a4e60d900ec
• Linux 2.6.27

Remediation

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