On Wed, 7 Aug 2019, syzbot wrote: > Hello, > > syzbot has tested the proposed patch but the reproducer still triggered > crash: > KASAN: use-after-free Read in device_release_driver_internal > > usb 4-1: USB disconnect, device number 2 > ================================================================== > BUG: KASAN: use-after-free in __lock_acquire+0x3a5d/0x5340 > kernel/locking/lockdep.c:3665 > Read of size 8 at addr ffff8881d4a54510 by task kworker/0:3/2876 > > CPU: 0 PID: 2876 Comm: kworker/0:3 Not tainted 5.2.0-rc6+ #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+0xca/0x13e lib/dump_stack.c:113 > print_address_description+0x67/0x231 mm/kasan/report.c:188 > __kasan_report.cold+0x1a/0x32 mm/kasan/report.c:317 > kasan_report+0xe/0x20 mm/kasan/common.c:614 > __lock_acquire+0x3a5d/0x5340 kernel/locking/lockdep.c:3665 > lock_acquire+0x100/0x2b0 kernel/locking/lockdep.c:4303 > __mutex_lock_common kernel/locking/mutex.c:926 [inline] > __mutex_lock+0xf9/0x12b0 kernel/locking/mutex.c:1073 > device_release_driver_internal+0x23/0x4c0 drivers/base/dd.c:1109 > bus_remove_device+0x2dc/0x4a0 drivers/base/bus.c:556 > device_del+0x460/0xb80 drivers/base/core.c:2274 > usb_disable_device+0x211/0x690 drivers/usb/core/message.c:1237 > usb_disconnect+0x284/0x830 drivers/usb/core/hub.c:2199 > hub_port_connect drivers/usb/core/hub.c:4949 [inline] > hub_port_connect_change drivers/usb/core/hub.c:5213 [inline] > port_event drivers/usb/core/hub.c:5359 [inline] > hub_event+0x13bd/0x3550 drivers/usb/core/hub.c:5441 > process_one_work+0x905/0x1570 kernel/workqueue.c:2269 > worker_thread+0x96/0xe20 kernel/workqueue.c:2415 > kthread+0x30b/0x410 kernel/kthread.c:255 > ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 > > Allocated by task 22: > save_stack+0x1b/0x80 mm/kasan/common.c:71 > set_track mm/kasan/common.c:79 [inline] > __kasan_kmalloc mm/kasan/common.c:489 [inline] > __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:462 > kmalloc include/linux/slab.h:547 [inline] > kzalloc include/linux/slab.h:742 [inline] > usb_set_configuration+0x2c4/0x1670 drivers/usb/core/message.c:1846 > generic_probe+0x9d/0xd5 drivers/usb/core/generic.c:210 > usb_probe_device+0x99/0x100 drivers/usb/core/driver.c:266 > really_probe+0x281/0x660 drivers/base/dd.c:509 > driver_probe_device+0x104/0x210 drivers/base/dd.c:670 > __device_attach_driver+0x1c2/0x220 drivers/base/dd.c:777 > bus_for_each_drv+0x15c/0x1e0 drivers/base/bus.c:454 > __device_attach+0x217/0x360 drivers/base/dd.c:843 > bus_probe_device+0x1e4/0x290 drivers/base/bus.c:514 > device_add+0xae6/0x16f0 drivers/base/core.c:2111 > usb_new_device.cold+0x6a4/0xe61 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+0x1abd/0x3550 drivers/usb/core/hub.c:5441 > process_one_work+0x905/0x1570 kernel/workqueue.c:2269 > worker_thread+0x96/0xe20 kernel/workqueue.c:2415 > kthread+0x30b/0x410 kernel/kthread.c:255 > ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 > > Freed by task 2876: > save_stack+0x1b/0x80 mm/kasan/common.c:71 > set_track mm/kasan/common.c:79 [inline] > __kasan_slab_free+0x130/0x180 mm/kasan/common.c:451 > slab_free_hook mm/slub.c:1421 [inline] > slab_free_freelist_hook mm/slub.c:1448 [inline] > slab_free mm/slub.c:2994 [inline] > kfree+0xd7/0x280 mm/slub.c:3949 > device_release+0x71/0x200 drivers/base/core.c:1064 > kobject_cleanup lib/kobject.c:691 [inline] > kobject_release lib/kobject.c:720 [inline] > kref_put include/linux/kref.h:65 [inline] > kobject_put+0x171/0x280 lib/kobject.c:737 > put_device+0x1b/0x30 drivers/base/core.c:2210 > klist_put+0xce/0x170 lib/klist.c:221 > bus_remove_device+0x3a4/0x4a0 drivers/base/bus.c:552 > device_del+0x460/0xb80 drivers/base/core.c:2274 > usb_disable_device+0x211/0x690 drivers/usb/core/message.c:1237 > usb_disconnect+0x284/0x830 drivers/usb/core/hub.c:2199 > hub_port_connect drivers/usb/core/hub.c:4949 [inline] > hub_port_connect_change drivers/usb/core/hub.c:5213 [inline] > port_event drivers/usb/core/hub.c:5359 [inline] > hub_event+0x13bd/0x3550 drivers/usb/core/hub.c:5441 > process_one_work+0x905/0x1570 kernel/workqueue.c:2269 > worker_thread+0x96/0xe20 kernel/workqueue.c:2415 > kthread+0x30b/0x410 kernel/kthread.c:255 > ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 > > The buggy address belongs to the object at ffff8881d4a54400 > which belongs to the cache kmalloc-2k of size 2048 > The buggy address is located 272 bytes inside of > 2048-byte region [ffff8881d4a54400, ffff8881d4a54c00) > The buggy address belongs to the page: > page:ffffea0007529400 refcount:1 mapcount:0 mapping:ffff8881dac02800 > index:0x0 compound_mapcount: 0 > flags: 0x200000000010200(slab|head) > raw: 0200000000010200 ffffea000753da00 0000000500000005 ffff8881dac02800 > raw: 0000000000000000 00000000000f000f 00000001ffffffff 0000000000000000 > page dumped because: kasan: bad access detected > > Memory state around the buggy address: > ffff8881d4a54400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ffff8881d4a54480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > > ffff8881d4a54500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ^ > ffff8881d4a54580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ffff8881d4a54600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ================================================================== > > > Tested on: > > commit: 6a3599ce usb-fuzzer: main usb gadget fuzzer driver > git tree: https://github.com/google/kasan.git > console output: https://syzkaller.appspot.com/x/log.txt?x=132aca2c600000 > kernel config: https://syzkaller.appspot.com/x/.config?x=700ca426ab83faae > compiler: gcc (GCC) 9.0.0 20181231 (experimental) Maybe this will help pinpoint where the problem occurs. The kernel log should indicate the before and after refcount values for the interface. Alan Stern #syz test: https://github.com/google/kasan.git 6a3599ce Index: usb-devel/drivers/usb/core/driver.c =================================================================== --- usb-devel.orig/drivers/usb/core/driver.c +++ usb-devel/drivers/usb/core/driver.c @@ -358,7 +358,11 @@ static int usb_probe_interface(struct de intf->needs_altsetting0 = 0; } + dev_info(&intf->dev, "Refcount before probe: %d\n", + refcount_read(&intf->dev.kobj.kref.refcount)); error = driver->probe(intf, id); + dev_info(&intf->dev, "Refcount after probe: %d\n", + refcount_read(&intf->dev.kobj.kref.refcount)); if (error) goto err;
