From a13cdb19fcb223ed41bdab3bab42b98dba87e90b Mon Sep 17 00:00:00 2001 From: Baul Lee Date: Sun, 26 Jul 2026 15:50:24 +0900 Subject: [PATCH] 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 Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: Federico Kirschbaum Reported-by: Baul Lee Cc: stable@vger.kernel.org Signed-off-by: Baul Lee Signed-off-by: Jiri Kosina --- drivers/hid/hid-core.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c index 2ae017845cd0..a82ab5ea9953 100644 --- a/drivers/hid/hid-core.c +++ b/drivers/hid/hid-core.c @@ -1933,13 +1933,14 @@ int hid_set_field(struct hid_field *field, unsigned offset, __s32 value) size = field->report_size; - hid_dump_input(field->report->device, field->usage + offset, value); - if (offset >= field->report_count) { hid_err(field->report->device, "offset (%d) exceeds report_count (%d)\n", offset, field->report_count); return -1; } + + hid_dump_input(field->report->device, field->usage + offset, value); + if (field->logical_minimum < 0) { if (value != snto32(s32ton(value, size), size)) { hid_err(field->report->device, "value %d is out of range\n", value);