HID: core: fix OOB read of field->usage in hid_set_field()

Overview

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

HID: core: fix OOB read of field->usage in hid_set_field()

hid_set_field() hands field->usage + offset to hid_dump_input() before the guard that bounds offset:

hid_dump_input(field->report->device, field->usage + offset, value);

if (offset >= field->report_count) {
	hid_err(...);
	return -1;
}

Under CONFIG_DEBUG_FS hid_dump_input() dereferences that pointer, with buf = hid_resolv_usage(usage->hid, NULL). The usage[] array is allocated inline with the hid_field in hid_register_field() and holds field->maxusage entries, so an offset past it reads off the end of the kvzalloc()ed allocation and into a neighbouring object. Had the guard run first, offset < report_count <= maxusage would already have confined the pointer to the array.

A caller supplies such an offset today. picolcd_fb_send_tile() validates only report->maxfield before issuing hid_set_field(report->field[0], 11 + i, ...) for i = 0..31, so its offsets are fixed at 11..42 and are never checked against the bound field. When the device registers that field with fewer usages, the framebuffer deferred-io work drives the read on every tile. KASAN reports a 4-byte slab-out-of-bounds read in hid_dump_input() below hid_set_field(), and the same boot logs "offset (1) exceeds report_count (1)" from the guard that runs only afterwards.

Move the hid_dump_input() call below the guard. Because field->maxusage >= field->report_count, the guard then establishes that field->usage + offset lies inside the array before it is dereferenced, for every caller and without changing behaviour on the valid path.

Discovered by XBOW, triaged by Baul Lee [email protected]

Affected

• Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 465544b3d6602cfbdc2305d5cbfb7f4954353b63
• Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 4993e1ab85d7d3f4a40d81852170f9665483bbd8
• Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 313ead1abed945544703b100a12c5a10fdf78409
• Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < c1d9c16af51cc6ff92a5a062617d3b022dd01078
• Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < a38212687519f2a72f43e62dec1348a690412404
• Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 9a1d7c5f0d82e8665715d5e47c9410c6a97e3748
• Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 5215ea00a747eca34cb2f603cfef91fef76c2558
• Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < cbcc0e8dea499e5ca86b583372ccb1815cccc570
• Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < a13cdb19fcb223ed41bdab3bab42b98dba87e90b
• Linux 2.6.12

Remediation

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