[PATCH] UBSAN: shift-out-of-bounds in set_flicker

[coolrrsh]

From: Rajeshwar R Shinde <coolrrsh@xxxxxxxxx>

Syzkaller reported the following issue:

UBSAN: shift-out-of-bounds in drivers/media/usb/gspca/cpia1.c:1031:27
shift exponent 245 is too large for 32-bit type 'int'
CPU: 1 PID: 25 Comm: kworker/1:1 
Not tainted 6.5.0-rc4-syzkaller-00118-g55c3e571d2a0 #0
Hardware name: 
Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023
Workqueue: usb_hub_wq hub_event
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x125/0x1b0 lib/dump_stack.c:106
 ubsan_epilogue lib/ubsan.c:217 [inline]
 __ubsan_handle_shift_out_of_bounds+0x27a/0x600 lib/ubsan.c:387
 set_flicker.cold+0x1b/0x20 drivers/media/usb/gspca/cpia1.c:1031
 sd_s_ctrl+0x2c6/0xbf0 drivers/media/usb/gspca/cpia1.c:1782
 __v4l2_ctrl_handler_setup+0x511/0x710 
drivers/media/v4l2-core/v4l2-ctrls-core.c:2481
 v4l2_ctrl_handler_setup 
drivers/media/v4l2-core/v4l2-ctrls-core.c:2498 [inline]
 v4l2_ctrl_handler_setup+0x50/0xa0 
drivers/media/v4l2-core/v4l2-ctrls-core.c:2490
 gspca_set_default_mode drivers/media/usb/gspca/gspca.c:908 [inline]
 gspca_dev_probe2+0xdd6/0x1b20 drivers/media/usb/gspca/gspca.c:1541
 gspca_dev_probe+0x18b/0x270 drivers/media/usb/gspca/gspca.c:1610
 usb_probe_interface+0x307/0x930 drivers/usb/core/driver.c:396
 call_driver_probe drivers/base/dd.c:579 [inline]
 really_probe+0x234/0xc90 drivers/base/dd.c:658
 __driver_probe_device+0x1de/0x4b0 drivers/base/dd.c:798
 driver_probe_device+0x4c/0x1a0 drivers/base/dd.c:828
 __device_attach_driver+0x1d4/0x300 drivers/base/dd.c:956
 bus_for_each_drv+0x157/0x1d0 drivers/base/bus.c:457
 __device_attach+0x1e8/0x4b0 drivers/base/dd.c:1028
 bus_probe_device+0x17c/0x1c0 drivers/base/bus.c:532
 device_add+0x11f1/0x1b40 drivers/base/core.c:3625
 usb_set_configuration+0x10cb/0x1c40 drivers/usb/core/message.c:2207
 usb_generic_driver_probe+0xca/0x130 drivers/usb/core/generic.c:238
 usb_probe_device+0xda/0x2c0 drivers/usb/core/driver.c:293
 call_driver_probe drivers/base/dd.c:579 [inline]
 really_probe+0x234/0xc90 drivers/base/dd.c:658
 __driver_probe_device+0x1de/0x4b0 drivers/base/dd.c:798
 driver_probe_device+0x4c/0x1a0 drivers/base/dd.c:828
 __device_attach_driver+0x1d4/0x300 drivers/base/dd.c:956
 bus_for_each_drv+0x157/0x1d0 drivers/base/bus.c:457
 __device_attach+0x1e8/0x4b0 drivers/base/dd.c:1028
 bus_probe_device+0x17c/0x1c0 drivers/base/bus.c:532
 device_add+0x11f1/0x1b40 drivers/base/core.c:3625
 usb_new_device+0xd80/0x1960 drivers/usb/core/hub.c:2589
 hub_port_connect drivers/usb/core/hub.c:5440 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5580 [inline]
 port_event drivers/usb/core/hub.c:5740 [inline]
 hub_event+0x2e62/0x4f30 drivers/usb/core/hub.c:5822
 process_one_work+0xaa2/0x16f0 kernel/workqueue.c:2597
 process_scheduled_works kernel/workqueue.c:2664 [inline]
 worker_thread+0x896/0x1110 kernel/workqueue.c:2750
 kthread+0x33a/0x430 kernel/kthread.c:389
 ret_from_fork+0x2c/0x70 arch/x86/kernel/process.c:145
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304
 </TASK>

shift-out-of-bounds error was triggered when sd->params.exposure.gain 
is right shifted beyond the bit range of int. Therefore added the 
conditional check before the shift operation.

Tested via syzbot.

Reported-by: syzbot+e27f3dbdab04e43b9f73@xxxxxxxxxxxxxxxxxxxxxxxxx

dashboard link: https://syzkaller.appspot.com/bug?extid=e27f3dbdab04e43b9f73

Signed-off-by: Rajeshwar R Shinde <coolrrsh@xxxxxxxxx>
---
 drivers/media/usb/gspca/cpia1.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/media/usb/gspca/cpia1.c b/drivers/media/usb/gspca/cpia1.c
index 46ed95483e22..bb22be99ea8c 100644
--- a/drivers/media/usb/gspca/cpia1.c
+++ b/drivers/media/usb/gspca/cpia1.c
@@ -1028,7 +1028,9 @@ static int set_flicker(struct gspca_dev *gspca_dev, int on, int apply)
 			sd->params.exposure.expMode = 2;
 			sd->exposure_status = EXPOSURE_NORMAL;
 		}
+		if(sd->params.exposure.gain < 32){
 		currentexp = currentexp << sd->params.exposure.gain;
+		}
 		sd->params.exposure.gain = 0;
 		/* round down current exposure to nearest value */
 		startexp = (currentexp + ROUND_UP_EXP_FOR_FLICKER) / cj;
-- 
2.25.1