HID: magicmouse: prevent unbounded recursion in magicmouse_raw_event()

Overview

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

HID: magicmouse: prevent unbounded recursion in magicmouse_raw_event()

magicmouse_raw_event() handles DOUBLE_REPORT_ID (0xf7) packets, which pack two touch reports into one, by splitting the packet and calling itself on each half. The only guard against runaway recursion is a "size < 1" check, which stops zero-sized calls but does not bound the recursion depth.

A malicious HID device that matches this driver can send a report starting with DOUBLE_REPORT_ID and filled with the sequence [0xf7, 0x00]. Each level consumes two bytes and recurses on the remainder, so an incoming report of up to HID_MAX_BUFFER_SIZE (16 KiB) drives roughly 8000 nested calls. That easily exhausts the 16 KiB kernel stack, leading to a stack overflow: a panic with CONFIG_VMAP_STACK, or memory corruption without it.

A double report only ever wraps two normal reports; it is never legitimately nested. Refuse to re-enter the DOUBLE_REPORT_ID case from a recursive call so the recursion depth is bounded to two, while all valid packets keep being parsed exactly as before.

Affected

• Linux >= a462230e16acc8664145216da3c928d03556691a < 26c45abed62536aabf4033fb6d64cf72e93374e9
• Linux >= a462230e16acc8664145216da3c928d03556691a < 8a10a624996f16628234306b46f0cf36707d78bd
• Linux >= a462230e16acc8664145216da3c928d03556691a < d16df755b4493b6d37803c628b2c621d096796a8
• Linux >= a462230e16acc8664145216da3c928d03556691a < bec338b07beb883726b32192c8f01c601bc76fda
• Linux >= a462230e16acc8664145216da3c928d03556691a < 70589b0c005db003f6d8ae4db3c4d54fed7b83e4
• Linux >= a462230e16acc8664145216da3c928d03556691a < a33a596d3ad8dfe6c96a368097a028abeee16c17
• Linux >= a462230e16acc8664145216da3c928d03556691a < d095de37f78c5f32a4252ef0f99b84ba76550b86
• Linux >= a462230e16acc8664145216da3c928d03556691a < db8d634128d2ba88d79c0b601e983ebe14bb0519
• Linux 2.6.37

Remediation

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