KMSAN: uninit-value in number

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    ba606e9d Revert "printk_safe: externalize printk_context"
git tree:       https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=1251b828e00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c07a3d4f8a59e198
dashboard link: https://syzkaller.appspot.com/bug?extid=9d42b7773d2fecd983ab
compiler:       clang version 9.0.0 (/home/glider/llvm/clang  
80fee25776c2fb61e74c1ecb1a523375c2500b69)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=140be8e4e00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13eb1edf600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+9d42b7773d2fecd983ab@xxxxxxxxxxxxxxxxxxxxxxxxx

usb 1-1: config 0 has no interface number 0
usb 1-1: New USB device found, idVendor=15a4, idProduct=9020,  
bcdDevice=ba.2a
usb 1-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
usb 1-1: config 0 descriptor??
=====================================================
BUG: KMSAN: uninit-value in number+0x32e/0x1e40 lib/vsprintf.c:436
CPU: 1 PID: 3904 Comm: kworker/1:2 Not tainted 5.4.0-rc3+ #0
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+0x128/0x220 mm/kmsan/kmsan_report.c:108
 __msan_warning+0x73/0xe0 mm/kmsan/kmsan_instr.c:245
 number+0x32e/0x1e40 lib/vsprintf.c:436
 vsnprintf+0x1e99/0x3210 lib/vsprintf.c:2576
 vscnprintf+0xc2/0x180 lib/vsprintf.c:2613
 vprintk_store+0xef/0x11e0 kernel/printk/printk.c:1921
 vprintk_emit+0x2fd/0x8d0 kernel/printk/printk.c:1984
 vprintk_default+0x90/0xa0 kernel/printk/printk.c:2029
 vprintk_func+0x635/0x810 kernel/printk/printk_safe.c:386
 printk+0x180/0x1c3 kernel/printk/printk.c:2062
 af9005_boot_packet+0xedc/0x17d0 drivers/media/usb/dvb-usb/af9005.c:607
 af9005_identify_state+0x13e/0x420 drivers/media/usb/dvb-usb/af9005.c:969
 dvb_usb_find_device drivers/media/usb/dvb-usb/dvb-usb-init.c:221 [inline]
 dvb_usb_device_init+0xb72/0x2e10  
drivers/media/usb/dvb-usb/dvb-usb-init.c:258
 af9005_usb_probe+0x73/0x80 drivers/media/usb/dvb-usb/af9005.c:992
 usb_probe_interface+0xd19/0x1310 drivers/usb/core/driver.c:361
 really_probe+0xd91/0x1f90 drivers/base/dd.c:552
 driver_probe_device+0x1ba/0x510 drivers/base/dd.c:721
 __device_attach_driver+0x5b8/0x790 drivers/base/dd.c:828
 bus_for_each_drv+0x28e/0x3b0 drivers/base/bus.c:430
 __device_attach+0x489/0x750 drivers/base/dd.c:894
 device_initial_probe+0x4a/0x60 drivers/base/dd.c:941
 bus_probe_device+0x131/0x390 drivers/base/bus.c:490
 device_add+0x25b5/0x2df0 drivers/base/core.c:2201
 usb_set_configuration+0x309f/0x3710 drivers/usb/core/message.c:2027
 generic_probe+0xe7/0x280 drivers/usb/core/generic.c:210
 usb_probe_device+0x146/0x200 drivers/usb/core/driver.c:266
 really_probe+0xd91/0x1f90 drivers/base/dd.c:552
 driver_probe_device+0x1ba/0x510 drivers/base/dd.c:721
 __device_attach_driver+0x5b8/0x790 drivers/base/dd.c:828
 bus_for_each_drv+0x28e/0x3b0 drivers/base/bus.c:430
 __device_attach+0x489/0x750 drivers/base/dd.c:894
 device_initial_probe+0x4a/0x60 drivers/base/dd.c:941
 bus_probe_device+0x131/0x390 drivers/base/bus.c:490
 device_add+0x25b5/0x2df0 drivers/base/core.c:2201
 usb_new_device+0x23e5/0x2fb0 drivers/usb/core/hub.c:2536
 hub_port_connect drivers/usb/core/hub.c:5098 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5213 [inline]
 port_event drivers/usb/core/hub.c:5359 [inline]
 hub_event+0x581d/0x72f0 drivers/usb/core/hub.c:5441
 process_one_work+0x1572/0x1ef0 kernel/workqueue.c:2269
 worker_thread+0x111b/0x2460 kernel/workqueue.c:2415
 kthread+0x4b5/0x4f0 kernel/kthread.c:256
 ret_from_fork+0x35/0x40 arch/x86/entry/entry_64.S:355

Local variable description: ----act_len@af9005_boot_packet
Variable was created at:
 af9005_boot_packet+0x98/0x17d0 drivers/media/usb/dvb-usb/af9005.c:559
 af9005_boot_packet+0x98/0x17d0 drivers/media/usb/dvb-usb/af9005.c:559
=====================================================


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