KMSAN: uninit-value in i2c_w

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    f75e4cfe kmsan: use kmsan_handle_urb() in urb.c
git tree:       kmsan
console output: https://syzkaller.appspot.com/x/log.txt?x=1514cdaaa00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=602468164ccdc30a
dashboard link: https://syzkaller.appspot.com/bug?extid=397fd082ce5143e2f67d
compiler:       clang version 9.0.0 (/home/glider/llvm/clang  
06d00afa61eef8f7f501ebdb4e8612ea43ec2d78)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12e7a54aa00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17ab35dea00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+397fd082ce5143e2f67d@xxxxxxxxxxxxxxxxxxxxxxxxx

usb 1-1: New USB device found, idVendor=06a2, idProduct=6810,  
bcdDevice=1b.af
usb 1-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
usb 1-1: string descriptor 0 read error: -71
gspca_main: gspca_topro-2.14.0 probing 06a2:6810
gspca_topro: reg_w err -71
==================================================================
BUG: KMSAN: uninit-value in i2c_w+0xb7a/0xd70  
drivers/media/usb/gspca/topro.c:1043
CPU: 1 PID: 3338 Comm: kworker/1:2 Not tainted 5.1.0+ #1
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: usb_hub_wq hub_event
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x191/0x1f0 lib/dump_stack.c:113
 kmsan_report+0x130/0x2a0 mm/kmsan/kmsan.c:622
 __msan_warning+0x75/0xe0 mm/kmsan/kmsan_instr.c:310
 i2c_w+0xb7a/0xd70 drivers/media/usb/gspca/topro.c:1043
 probe_6810 drivers/media/usb/gspca/topro.c:1126 [inline]
 sd_init+0xc05/0x7ca0 drivers/media/usb/gspca/topro.c:4081
 gspca_dev_probe2+0xee0/0x2240 drivers/media/usb/gspca/gspca.c:1546
 gspca_dev_probe+0x346/0x3b0 drivers/media/usb/gspca/gspca.c:1619
 sd_probe+0x8d/0xa0 drivers/media/usb/gspca/gl860/gl860.c:523
 usb_probe_interface+0xd66/0x1320 drivers/usb/core/driver.c:361
 really_probe+0xdae/0x1d80 drivers/base/dd.c:513
 driver_probe_device+0x1b3/0x4f0 drivers/base/dd.c:671
 __device_attach_driver+0x5b8/0x790 drivers/base/dd.c:778
 bus_for_each_drv+0x28e/0x3b0 drivers/base/bus.c:454
 __device_attach+0x454/0x730 drivers/base/dd.c:844
 device_initial_probe+0x4a/0x60 drivers/base/dd.c:891
 bus_probe_device+0x137/0x390 drivers/base/bus.c:514
 device_add+0x288d/0x30e0 drivers/base/core.c:2106
 usb_set_configuration+0x30dc/0x3750 drivers/usb/core/message.c:2027
 generic_probe+0xe7/0x280 drivers/usb/core/generic.c:210
 usb_probe_device+0x14c/0x200 drivers/usb/core/driver.c:266
 really_probe+0xdae/0x1d80 drivers/base/dd.c:513
 driver_probe_device+0x1b3/0x4f0 drivers/base/dd.c:671
 __device_attach_driver+0x5b8/0x790 drivers/base/dd.c:778
 bus_for_each_drv+0x28e/0x3b0 drivers/base/bus.c:454
 __device_attach+0x454/0x730 drivers/base/dd.c:844
 device_initial_probe+0x4a/0x60 drivers/base/dd.c:891
 bus_probe_device+0x137/0x390 drivers/base/bus.c:514
 device_add+0x288d/0x30e0 drivers/base/core.c:2106
 usb_new_device+0x23e5/0x2ff0 drivers/usb/core/hub.c:2534
 hub_port_connect drivers/usb/core/hub.c:5089 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5204 [inline]
 port_event drivers/usb/core/hub.c:5350 [inline]
 hub_event+0x48d1/0x7290 drivers/usb/core/hub.c:5432
 process_one_work+0x1572/0x1f00 kernel/workqueue.c:2269
 worker_thread+0x111b/0x2460 kernel/workqueue.c:2415
 kthread+0x4b5/0x4f0 kernel/kthread.c:254
 ret_from_fork+0x35/0x40 arch/x86/entry/entry_64.S:355

Uninit was created at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:208 [inline]
 kmsan_internal_poison_shadow+0x92/0x150 mm/kmsan/kmsan.c:162
 kmsan_kmalloc+0xa4/0x130 mm/kmsan/kmsan_hooks.c:175
 kmem_cache_alloc_trace+0x503/0xae0 mm/slub.c:2801
 kmalloc include/linux/slab.h:547 [inline]
 gspca_dev_probe2+0x30c/0x2240 drivers/media/usb/gspca/gspca.c:1480
 gspca_dev_probe+0x346/0x3b0 drivers/media/usb/gspca/gspca.c:1619
 sd_probe+0x8d/0xa0 drivers/media/usb/gspca/gl860/gl860.c:523
 usb_probe_interface+0xd66/0x1320 drivers/usb/core/driver.c:361
 really_probe+0xdae/0x1d80 drivers/base/dd.c:513
 driver_probe_device+0x1b3/0x4f0 drivers/base/dd.c:671
 __device_attach_driver+0x5b8/0x790 drivers/base/dd.c:778
 bus_for_each_drv+0x28e/0x3b0 drivers/base/bus.c:454
 __device_attach+0x454/0x730 drivers/base/dd.c:844
 device_initial_probe+0x4a/0x60 drivers/base/dd.c:891
 bus_probe_device+0x137/0x390 drivers/base/bus.c:514
 device_add+0x288d/0x30e0 drivers/base/core.c:2106
 usb_set_configuration+0x30dc/0x3750 drivers/usb/core/message.c:2027
 generic_probe+0xe7/0x280 drivers/usb/core/generic.c:210
 usb_probe_device+0x14c/0x200 drivers/usb/core/driver.c:266
 really_probe+0xdae/0x1d80 drivers/base/dd.c:513
 driver_probe_device+0x1b3/0x4f0 drivers/base/dd.c:671
 __device_attach_driver+0x5b8/0x790 drivers/base/dd.c:778
 bus_for_each_drv+0x28e/0x3b0 drivers/base/bus.c:454
 __device_attach+0x454/0x730 drivers/base/dd.c:844
 device_initial_probe+0x4a/0x60 drivers/base/dd.c:891
 bus_probe_device+0x137/0x390 drivers/base/bus.c:514
 device_add+0x288d/0x30e0 drivers/base/core.c:2106
 usb_new_device+0x23e5/0x2ff0 drivers/usb/core/hub.c:2534
 hub_port_connect drivers/usb/core/hub.c:5089 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5204 [inline]
 port_event drivers/usb/core/hub.c:5350 [inline]
 hub_event+0x48d1/0x7290 drivers/usb/core/hub.c:5432
 process_one_work+0x1572/0x1f00 kernel/workqueue.c:2269
 worker_thread+0x111b/0x2460 kernel/workqueue.c:2415
 kthread+0x4b5/0x4f0 kernel/kthread.c:254
 ret_from_fork+0x35/0x40 arch/x86/entry/entry_64.S:355
==================================================================


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