KASAN: use-after-free Read in rc_dev_uevent

[syzbot <syzbot+ceef16277388d6f24898@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    7b4ea945 Revert "x86/mm/64: Do not sync vmalloc/ioremap ma..
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing
console output: https://syzkaller.appspot.com/x/log.txt?x=11a7813a900000
kernel config:  https://syzkaller.appspot.com/x/.config?x=72a84c46d0c668c
dashboard link: https://syzkaller.appspot.com/bug?extid=ceef16277388d6f24898
compiler:       gcc (GCC) 10.1.0-syz 20200507

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ceef16277388d6f24898@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in string_nocheck lib/vsprintf.c:611 [inline]
BUG: KASAN: use-after-free in string+0x39c/0x3d0 lib/vsprintf.c:693
Read of size 1 at addr ffff8881ca21cd20 by task systemd-udevd/5147

CPU: 1 PID: 5147 Comm: systemd-udevd Not tainted 5.8.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0xf6/0x16e lib/dump_stack.c:118
 print_address_description.constprop.0+0x1a/0x210 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report.cold+0x37/0x7c mm/kasan/report.c:530
 string_nocheck lib/vsprintf.c:611 [inline]
 string+0x39c/0x3d0 lib/vsprintf.c:693
 vsnprintf+0x71b/0x14f0 lib/vsprintf.c:2617
 add_uevent_var+0x14d/0x310 lib/kobject_uevent.c:664
 rc_dev_uevent+0x54/0x140 drivers/media/rc/rc-main.c:1616
 dev_uevent+0x30e/0x780 drivers/base/core.c:1916
 uevent_show+0x1bb/0x360 drivers/base/core.c:1963
 dev_attr_show+0x4b/0x90 drivers/base/core.c:1667
 sysfs_kf_seq_show+0x1f8/0x400 fs/sysfs/file.c:60
 seq_read+0x432/0x1070 fs/seq_file.c:208
 kernfs_fop_read+0xe9/0x590 fs/kernfs/file.c:251
 vfs_read+0x1df/0x520 fs/read_write.c:479
 ksys_read+0x12d/0x250 fs/read_write.c:607
 do_syscall_64+0x2d/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7f6e6c02f910
Code: b6 fe ff ff 48 8d 3d 0f be 08 00 48 83 ec 08 e8 06 db 01 00 66 0f 1f 44 00 00 83 3d f9 2d 2c 00 00 75 10 b8 00 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 31 c3 48 83 ec 08 e8 de 9b 01 00 48 89 04 24
RSP: 002b:00007fff3cddeae8 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 0000558492caaae0 RCX: 00007f6e6c02f910
RDX: 0000000000001000 RSI: 0000558492cc7530 RDI: 0000000000000007
RBP: 00007f6e6c2ea440 R08: 00007f6e6c2ee298 R09: 0000000000001010
R10: 0000558492caaae0 R11: 0000000000000246 R12: 0000000000001000
R13: 0000000000000d68 R14: 0000558492cc7530 R15: 00007f6e6c2e9900

Allocated by task 5:
 save_stack+0x1b/0x40 mm/kasan/common.c:48
 set_track mm/kasan/common.c:56 [inline]
 __kasan_kmalloc.constprop.0+0xc2/0xd0 mm/kasan/common.c:494
 slab_post_alloc_hook mm/slab.h:586 [inline]
 slab_alloc_node mm/slub.c:2824 [inline]
 slab_alloc mm/slub.c:2832 [inline]
 __kmalloc_track_caller+0xec/0x280 mm/slub.c:4430
 kstrdup+0x36/0x70 mm/util.c:60
 ir_create_table drivers/media/rc/rc-main.c:217 [inline]
 ir_setkeytable drivers/media/rc/rc-main.c:477 [inline]
 rc_prepare_rx_device drivers/media/rc/rc-main.c:1786 [inline]
 rc_register_device+0x464/0x1600 drivers/media/rc/rc-main.c:1914
 igorplugusb_probe+0x7e6/0xc98 drivers/media/rc/igorplugusb.c:209
 usb_probe_interface+0x315/0x7f0 drivers/usb/core/driver.c:374
 really_probe+0x291/0xde0 drivers/base/dd.c:553
 driver_probe_device+0x26b/0x3d0 drivers/base/dd.c:738
 __device_attach_driver+0x1d1/0x290 drivers/base/dd.c:844
 bus_for_each_drv+0x15f/0x1e0 drivers/base/bus.c:431
 __device_attach+0x228/0x4a0 drivers/base/dd.c:912
 bus_probe_device+0x1e4/0x290 drivers/base/bus.c:491
 device_add+0xb51/0x1c70 drivers/base/core.c:2930
 usb_set_configuration+0xf05/0x18a0 drivers/usb/core/message.c:2032
 usb_generic_driver_probe+0xba/0xf2 drivers/usb/core/generic.c:239
 usb_probe_device+0xd9/0x250 drivers/usb/core/driver.c:272
 really_probe+0x291/0xde0 drivers/base/dd.c:553
 driver_probe_device+0x26b/0x3d0 drivers/base/dd.c:738
 __device_attach_driver+0x1d1/0x290 drivers/base/dd.c:844
 bus_for_each_drv+0x15f/0x1e0 drivers/base/bus.c:431
 __device_attach+0x228/0x4a0 drivers/base/dd.c:912
 bus_probe_device+0x1e4/0x290 drivers/base/bus.c:491
 device_add+0xb51/0x1c70 drivers/base/core.c:2930
 usb_new_device.cold+0x71d/0xfd4 drivers/usb/core/hub.c:2554
 hub_port_connect drivers/usb/core/hub.c:5208 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5348 [inline]
 port_event drivers/usb/core/hub.c:5494 [inline]
 hub_event+0x2361/0x4390 drivers/usb/core/hub.c:5576
 process_one_work+0x94c/0x15f0 kernel/workqueue.c:2269
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
 kthread+0x392/0x470 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

Freed by task 5:
 save_stack+0x1b/0x40 mm/kasan/common.c:48
 set_track mm/kasan/common.c:56 [inline]
 kasan_set_free_info mm/kasan/common.c:316 [inline]
 __kasan_slab_free+0x116/0x160 mm/kasan/common.c:455
 slab_free_hook mm/slub.c:1474 [inline]
 slab_free_freelist_hook+0x53/0x140 mm/slub.c:1507
 slab_free mm/slub.c:3072 [inline]
 kfree+0xbc/0x2c0 mm/slub.c:4052
 ir_free_table drivers/media/rc/rc-main.c:245 [inline]
 rc_free_rx_device drivers/media/rc/rc-main.c:1875 [inline]
 rc_unregister_device+0x142/0x410 drivers/media/rc/rc-main.c:2014
 igorplugusb_disconnect+0x58/0x110 drivers/media/rc/igorplugusb.c:232
 usb_unbind_interface+0x1d8/0x8d0 drivers/usb/core/driver.c:436
 __device_release_driver+0x3c6/0x6f0 drivers/base/dd.c:1153
 device_release_driver_internal drivers/base/dd.c:1184 [inline]
 device_release_driver+0x26/0x40 drivers/base/dd.c:1207
 bus_remove_device+0x2eb/0x5a0 drivers/base/bus.c:533
 device_del+0x481/0xd90 drivers/base/core.c:3107
 usb_disable_device+0x387/0x930 drivers/usb/core/message.c:1245
 usb_disconnect.cold+0x27d/0x780 drivers/usb/core/hub.c:2217
 hub_port_connect drivers/usb/core/hub.c:5059 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5348 [inline]
 port_event drivers/usb/core/hub.c:5494 [inline]
 hub_event+0x1c93/0x4390 drivers/usb/core/hub.c:5576
 process_one_work+0x94c/0x15f0 kernel/workqueue.c:2269
 process_scheduled_works kernel/workqueue.c:2331 [inline]
 worker_thread+0x82b/0x1120 kernel/workqueue.c:2417
 kthread+0x392/0x470 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

The buggy address belongs to the object at ffff8881ca21cd20
 which belongs to the cache kmalloc-16 of size 16
The buggy address is located 0 bytes inside of
 16-byte region [ffff8881ca21cd20, ffff8881ca21cd30)
The buggy address belongs to the page:
page:ffffea0007288700 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0x200000000000200(slab)
raw: 0200000000000200 0000000000000000 0000000100000001 ffff8881da003680
raw: 0000000000000000 0000000080800080 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8881ca21cc00: fb fb fc fc fb fb fc fc fb fb fc fc 00 00 fc fc
 ffff8881ca21cc80: fb fb fc fc 00 00 fc fc 00 00 fc fc 00 00 fc fc
>ffff8881ca21cd00: fb fb fc fc fb fb fc fc fb fb fc fc 00 00 fc fc
                               ^
 ffff8881ca21cd80: 00 00 fc fc fb fb fc fc fb fb fc fc fb fb fc fc
 ffff8881ca21ce00: 00 00 fc fc fb fb fc fc 00 00 fc fc 00 00 fc fc
==================================================================


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