CVE-2021-47097

In the Linux kernel, the following vulnerability has been resolved: Input:
elantech - fix stack out of bound access in elantech_change_report_id() The
array param[] in elantech_change_report_id() must be at least 3 bytes,
because elantech_read_reg_params() is calling ps2_command() with
PSMOUSE_CMD_GETINFO, that is going to access 3 bytes from param[], but it’s
defined in the stack as an array of 2 bytes, therefore we have a potential
stack out-of-bounds access here, also confirmed by KASAN: [ 6.512374] BUG:
KASAN: stack-out-of-bounds in __ps2_command+0x372/0x7e0 [ 6.512397] Read of
size 1 at addr ffff8881024d77c2 by task kworker/2:1/118 [ 6.512416] CPU: 2
PID: 118 Comm: kworker/2:1 Not tainted 5.13.0-22-generic #22+arighi20211110
[ 6.512428] Hardware name: LENOVO 20T8000QGE/20T8000QGE, BIOS R1AET32W
(1.08 ) 08/14/2020 [ 6.512436] Workqueue: events_long serio_handle_event [
6.512453] Call Trace: [ 6.512462] show_stack+0x52/0x58 [ 6.512474]
dump_stack+0xa1/0xd3 [ 6.512487]
print_address_description.constprop.0+0x1d/0x140 [ 6.512502] ?
__ps2_command+0x372/0x7e0 [ 6.512516] __kasan_report.cold+0x7d/0x112 [
6.512527] ? _raw_write_lock_irq+0x20/0xd0 [ 6.512539] ?
__ps2_command+0x372/0x7e0 [ 6.512552] kasan_report+0x3c/0x50 [ 6.512564]
__asan_load1+0x6a/0x70 [ 6.512575] __ps2_command+0x372/0x7e0 [ 6.512589] ?
ps2_drain+0x240/0x240 [ 6.512601] ? dev_printk_emit+0xa2/0xd3 [ 6.512612] ?
dev_vprintk_emit+0xc5/0xc5 [ 6.512621] ? __kasan_check_write+0x14/0x20 [
6.512634] ? mutex_lock+0x8f/0xe0 [ 6.512643] ?
__mutex_lock_slowpath+0x20/0x20 [ 6.512655] ps2_command+0x52/0x90 [
6.512670] elantech_ps2_command+0x4f/0xc0 [psmouse] [ 6.512734]
elantech_change_report_id+0x1e6/0x256 [psmouse] [ 6.512799] ?
elantech_report_trackpoint.constprop.0.cold+0xd/0xd [psmouse] [ 6.512863] ?
ps2_command+0x7f/0x90 [ 6.512877] elantech_query_info.cold+0x6bd/0x9ed
[psmouse] [ 6.512943] ? elantech_setup_ps2+0x460/0x460 [psmouse] [
6.513005] ? psmouse_reset+0x69/0xb0 [psmouse] [ 6.513064] ?
psmouse_attr_set_helper+0x2a0/0x2a0 [psmouse] [ 6.513122] ?
phys_pmd_init+0x30e/0x521 [ 6.513137] elantech_init+0x8a/0x200 [psmouse] [
6.513200] ? elantech_init_ps2+0xf0/0xf0 [psmouse] [ 6.513249] ?
elantech_query_info+0x440/0x440 [psmouse] [ 6.513296] ?
synaptics_send_cmd+0x60/0x60 [psmouse] [ 6.513342] ?
elantech_query_info+0x440/0x440 [psmouse] [ 6.513388] ?
psmouse_try_protocol+0x11e/0x170 [psmouse] [ 6.513432]
psmouse_extensions+0x65d/0x6e0 [psmouse] [ 6.513476] ?
psmouse_try_protocol+0x170/0x170 [psmouse] [ 6.513519] ?
mutex_unlock+0x22/0x40 [ 6.513526] ? ps2_command+0x7f/0x90 [ 6.513536] ?
psmouse_probe+0xa3/0xf0 [psmouse] [ 6.513580]
psmouse_switch_protocol+0x27d/0x2e0 [psmouse] [ 6.513624]
psmouse_connect+0x272/0x530 [psmouse] [ 6.513669]
serio_driver_probe+0x55/0x70 [ 6.513679] really_probe+0x190/0x720 [
6.513689] driver_probe_device+0x160/0x1f0 [ 6.513697]
device_driver_attach+0x119/0x130 [ 6.513705] ?
device_driver_attach+0x130/0x130 [ 6.513713] __driver_attach+0xe7/0x1a0 [
6.513720] ? device_driver_attach+0x130/0x130 [ 6.513728]
bus_for_each_dev+0xfb/0x150 [ 6.513738] ? subsys_dev_iter_exit+0x10/0x10 [
6.513748] ? _raw_write_unlock_bh+0x30/0x30 [ 6.513757]
driver_attach+0x2d/0x40 [ 6.513764] serio_handle_event+0x199/0x3d0 [
6.513775] process_one_work+0x471/0x740 [ 6.513785]
worker_thread+0x2d2/0x790 [ 6.513794] ? process_one_work+0x740/0x740 [
6.513802] kthread+0x1b4/0x1e0 [ 6.513809] ? set_kthread_struct+0x80/0x80 [
6.513816] ret_from_fork+0x22/0x30 [ 6.513832] The buggy address belongs to
the page: [ 6.513838] page:00000000bc35e189 refcount:0 mapcount:0
mapping:0000000000000000 index:0x0 pfn:0x1024d7 [ 6.513847] flags:
0x17ffffc0000000(node=0|zone=2|lastcpupid=0x1fffff) [ 6.513860] raw: 0
—truncated—