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Subject[PATCH 5.15 051/128] Input: elantech - fix stack out of bound access in elantech_change_report_id()
Date
From: Andrea Righi <andrea.righi@canonical.com>

[ Upstream commit 1d72d9f960ccf1052a0630a68c3d358791dbdaaa ]

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: 0017ffffc0000000 dead000000000100 dead000000000122 0000000000000000
[ 6.513867] raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
[ 6.513872] page dumped because: kasan: bad access detected

[ 6.513879] addr ffff8881024d77c2 is located in stack of task kworker/2:1/118 at offset 34 in frame:
[ 6.513887] elantech_change_report_id+0x0/0x256 [psmouse]

[ 6.513941] this frame has 1 object:
[ 6.513947] [32, 34) 'param'

[ 6.513956] Memory state around the buggy address:
[ 6.513962] ffff8881024d7680: f2 f2 f2 f2 f2 00 00 f3 f3 00 00 00 00 00 00 00
[ 6.513969] ffff8881024d7700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[ 6.513976] >ffff8881024d7780: 00 00 00 00 f1 f1 f1 f1 02 f3 f3 f3 00 00 00 00
[ 6.513982] ^
[ 6.513988] ffff8881024d7800: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[ 6.513995] ffff8881024d7880: 00 f1 f1 f1 f1 03 f2 03 f2 03 f3 f3 f3 00 00 00
[ 6.514000] ==================================================================

Define param[] in elantech_change_report_id() as an array of 3 bytes to
prevent the out-of-bounds access in the stack.

Fixes: e4c9062717fe ("Input: elantech - fix protocol errors for some trackpoints in SMBus mode")
BugLink: https://bugs.launchpad.net/bugs/1945590
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Reviewed-by: Wolfram Sang <wsa@kernel.org>
Link: https://lore.kernel.org/r/20211116095559.24395-1-andrea.righi@canonical.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/input/mouse/elantech.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/input/mouse/elantech.c b/drivers/input/mouse/elantech.c
index 956d9cd347964..ece97f8c6a3e3 100644
--- a/drivers/input/mouse/elantech.c
+++ b/drivers/input/mouse/elantech.c
@@ -1588,7 +1588,13 @@ static const struct dmi_system_id no_hw_res_dmi_table[] = {
*/
static int elantech_change_report_id(struct psmouse *psmouse)
{
- unsigned char param[2] = { 0x10, 0x03 };
+ /*
+ * NOTE: the code is expecting to receive param[] as an array of 3
+ * items (see __ps2_command()), even if in this case only 2 are
+ * actually needed. Make sure the array size is 3 to avoid potential
+ * stack out-of-bound accesses.
+ */
+ unsigned char param[3] = { 0x10, 0x03 };

if (elantech_write_reg_params(psmouse, 0x7, param) ||
elantech_read_reg_params(psmouse, 0x7, param) ||
--
2.34.1


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