CVE-2026-80781: HID: core: fix OOB read of field->usage in hid_set_field()

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

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 <baul.lee@xbow.com>

The Linux kernel CVE team has assigned CVE-2026-80781 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 5.10.267 with commit 465544b3d6602cfbdc2305d5cbfb7f4954353b63
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 5.15.218 with commit 4993e1ab85d7d3f4a40d81852170f9665483bbd8
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 6.1.185 with commit 313ead1abed945544703b100a12c5a10fdf78409
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 6.6.154 with commit c1d9c16af51cc6ff92a5a062617d3b022dd01078
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 6.12.106 with commit a38212687519f2a72f43e62dec1348a690412404
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 6.18.47 with commit 9a1d7c5f0d82e8665715d5e47c9410c6a97e3748
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 7.1.11 with commit 5215ea00a747eca34cb2f603cfef91fef76c2558
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 7.2.1 with commit cbcc0e8dea499e5ca86b583372ccb1815cccc570
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 7.3-rc1 with commit a13cdb19fcb223ed41bdab3bab42b98dba87e90b

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-80781
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	drivers/hid/hid-core.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/465544b3d6602cfbdc2305d5cbfb7f4954353b63
	https://git.kernel.org/stable/c/4993e1ab85d7d3f4a40d81852170f9665483bbd8
	https://git.kernel.org/stable/c/313ead1abed945544703b100a12c5a10fdf78409
	https://git.kernel.org/stable/c/c1d9c16af51cc6ff92a5a062617d3b022dd01078
	https://git.kernel.org/stable/c/a38212687519f2a72f43e62dec1348a690412404
	https://git.kernel.org/stable/c/9a1d7c5f0d82e8665715d5e47c9410c6a97e3748
	https://git.kernel.org/stable/c/5215ea00a747eca34cb2f603cfef91fef76c2558
	https://git.kernel.org/stable/c/cbcc0e8dea499e5ca86b583372ccb1815cccc570
	https://git.kernel.org/stable/c/a13cdb19fcb223ed41bdab3bab42b98dba87e90b