On Fri, Aug 07, 2020 at 09:55:40PM +0800, Hillf Danton wrote: > > On Fri, 7 Aug 2020 10:15:04 +0100 Sean Young wrote: > > On Fri, Aug 07, 2020 at 12:26:29AM -0700, syzbot wrote: > > > 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@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > > > ================================================================== > > > 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 > > > > This thread is reading the uevent sysfs file, which reads > > rc_dev->map.name, and also rc_dev->device_name, but that is not causing > > problems is this case. > > > > > > > > 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 > > > > .. this probed the device .. > > > > > 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 > > > > This unplugged the device, and freed rc_dev->map->name and sets > > it to NULL. There is no locking between the two threads so this is > > a race condition. > > > > I think there are worse, related problems here. For example, iguanair > > driver allocates rc_dev->device_name and frees it in its usb disconnect > > handler. This field is also read by uevent, and not set to null by > > the disconnect handler. > > > > Not sure what the best solution is yet. > > See if the diff below makes ant-antenna-size sense. > > > > > Thanks > > > > Sean > > > > > 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 > > > ================================================================== > > Handle uevent under dev's lock to serialize with the unregistering of > dev. I think this is the right solution. The problem is devm_rc_register_device() type drivers might allocate device_name/driver_name and free them before the rc device is unregistered through devm, but after reviewing none of those drivers do that. > --- a/drivers/media/rc/rc-main.c > +++ b/drivers/media/rc/rc-main.c > @@ -1576,12 +1576,21 @@ static int rc_dev_uevent(struct device * > { > struct rc_dev *dev = to_rc_dev(device); > > + if (!dev->registered) > + return -ENODEV; > + > + mutex_lock(&dev->lock); > + if (!dev->registered) { > + mutex_unlock(&dev->lock); > + return -ENODEV; > + } Checking registered twice is not the right thing to do. > if (dev->rc_map.name) > ADD_HOTPLUG_VAR("NAME=%s", dev->rc_map.name); > if (dev->driver_name) > ADD_HOTPLUG_VAR("DRV_NAME=%s", dev->driver_name); > if (dev->device_name) > ADD_HOTPLUG_VAR("DEV_NAME=%s", dev->device_name); > + mutex_unlock(&dev->lock); > > return 0; > } > @@ -1970,13 +1979,12 @@ void rc_unregister_device(struct rc_dev > del_timer_sync(&dev->timer_keyup); > del_timer_sync(&dev->timer_repeat); > > - rc_free_rx_device(dev); > - > mutex_lock(&dev->lock); > if (dev->users && dev->close) > dev->close(dev); > dev->registered = false; > mutex_unlock(&dev->lock); > + rc_free_rx_device(dev); The ordering here can introduce subtle bugs but this is fine. > > /* > * lirc device should be freed with dev->registered = false, so This patch also needs a signed-off-by. Thanks, Sean
