On Fri, Dec 18, 2020 at 04:21:13PM +0800, Hillf Danton wrote: > On Thu, 17 Dec 2020 19:21:10 -0800 > > syzbot has found a reproducer for the following issue on: > > > > HEAD commit: 5e60366d Merge tag 'fallthrough-fixes-clang-5.11-rc1' of g.. > > 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=12c5b623500000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=5cea7506b7139727 > > dashboard link: https://syzkaller.appspot.com/bug?extid=9e04e2df4a32fb661daf > > compiler: gcc (GCC) 10.1.0-syz 20200507 > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=175adf07500000 > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1672680f500000 > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > Reported-by: syzbot+9e04e2df4a32fb661daf@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > ================================================================== > > BUG: KASAN: use-after-free in usb_submit_urb+0x1210/0x1560 drivers/usb/core/urb.c:383 > > Read of size 4 at addr ffff888101d21018 by task syz-executor166/4405 > > > > CPU: 0 PID: 4405 Comm: syz-executor166 Not tainted 5.10.0-syzkaller #0 > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > > Call Trace: > > __dump_stack lib/dump_stack.c:79 [inline] > > dump_stack+0x107/0x163 lib/dump_stack.c:120 > > print_address_description.constprop.0.cold+0xae/0x4c8 mm/kasan/report.c:385 > > __kasan_report mm/kasan/report.c:545 [inline] > > kasan_report.cold+0x1f/0x37 mm/kasan/report.c:562 > > usb_submit_urb+0x1210/0x1560 drivers/usb/core/urb.c:383 > > service_outstanding_interrupt.part.0+0x5f/0xa0 drivers/usb/class/cdc-wdm.c:470 > > service_outstanding_interrupt drivers/usb/class/cdc-wdm.c:465 [inline] > > wdm_read+0x9a0/0xbd0 drivers/usb/class/cdc-wdm.c:583 > > vfs_read+0x1b5/0x570 fs/read_write.c:494 > > ksys_read+0x12d/0x250 fs/read_write.c:634 > > do_syscall_64+0x2d/0x40 arch/x86/entry/common.c:46 > > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > RIP: 0033:0x44b529 > > Code: e8 bc b4 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 8b cb fb ff c3 66 2e 0f 1f 84 00 00 00 00 > > RSP: 002b:00007f2dfcb6ed98 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 > > RAX: ffffffffffffffda RBX: 00000000006dcc38 RCX: 000000000044b529 > > RDX: 0000000000001000 RSI: 0000000020001000 RDI: 0000000000000004 > > RBP: 00000000006dcc30 R08: 0000000000000000 R09: 0000000000000000 > > R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dcc3c > > R13: 0142006002090100 R14: 04010040a4157d25 R15: 4000000200000112 > > > > Allocated by task 2632: > > kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48 > > kasan_set_track mm/kasan/common.c:56 [inline] > > __kasan_kmalloc.constprop.0+0xc2/0xd0 mm/kasan/common.c:461 > > kmalloc include/linux/slab.h:552 [inline] > > kzalloc include/linux/slab.h:682 [inline] > > usb_alloc_dev+0x51/0xef0 drivers/usb/core/usb.c:582 > > hub_port_connect drivers/usb/core/hub.c:5129 [inline] > > hub_port_connect_change drivers/usb/core/hub.c:5363 [inline] > > port_event drivers/usb/core/hub.c:5509 [inline] > > hub_event+0x1def/0x42d0 drivers/usb/core/hub.c:5591 > > process_one_work+0x98d/0x15c0 kernel/workqueue.c:2275 > > worker_thread+0x64c/0x1120 kernel/workqueue.c:2421 > > kthread+0x38c/0x460 kernel/kthread.c:292 > > ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296 > > > > Freed by task 2181: > > kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48 > > kasan_set_track+0x1c/0x30 mm/kasan/common.c:56 > > kasan_set_free_info+0x1b/0x30 mm/kasan/generic.c:352 > > __kasan_slab_free+0x102/0x140 mm/kasan/common.c:422 > > slab_free_hook mm/slub.c:1544 [inline] > > slab_free_freelist_hook+0x5d/0x150 mm/slub.c:1577 > > slab_free mm/slub.c:3140 [inline] > > kfree+0xdb/0x3a0 mm/slub.c:4122 > > device_release+0x9f/0x240 drivers/base/core.c:1962 > > kobject_cleanup lib/kobject.c:705 [inline] > > kobject_release lib/kobject.c:736 [inline] > > kref_put include/linux/kref.h:65 [inline] > > kobject_put+0x1c8/0x540 lib/kobject.c:753 > > put_device+0x1b/0x30 drivers/base/core.c:3190 > > hub_port_connect drivers/usb/core/hub.c:5074 [inline] > > hub_port_connect_change drivers/usb/core/hub.c:5363 [inline] > > port_event drivers/usb/core/hub.c:5509 [inline] > > hub_event+0x1c8a/0x42d0 drivers/usb/core/hub.c:5591 > > process_one_work+0x98d/0x15c0 kernel/workqueue.c:2275 > > worker_thread+0x64c/0x1120 kernel/workqueue.c:2421 > > kthread+0x38c/0x460 kernel/kthread.c:292 > > ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296 > > > > The buggy address belongs to the object at ffff888101d21000 > > which belongs to the cache kmalloc-2k of size 2048 > > The buggy address is located 24 bytes inside of > > 2048-byte region [ffff888101d21000, ffff888101d21800) > > The buggy address belongs to the page: > > page:0000000019761127 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x101d20 > > head:0000000019761127 order:3 compound_mapcount:0 compound_pincount:0 > > flags: 0x200000000010200(slab|head) > > raw: 0200000000010200 dead000000000100 dead000000000122 ffff888100042000 > > raw: 0000000000000000 0000000080080008 00000001ffffffff 0000000000000000 > > page dumped because: kasan: bad access detected > > > > Memory state around the buggy address: > > ffff888101d20f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc > > ffff888101d20f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc > > >ffff888101d21000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > > ^ > > ffff888101d21080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > > ffff888101d21100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > > ================================================================== > > > Bail out without urb submitted if wdm device is disconnecting. > > --- a/drivers/usb/class/cdc-wdm.c > +++ b/drivers/usb/class/cdc-wdm.c > @@ -474,18 +474,25 @@ out: > return rv; > } > > -static ssize_t wdm_read > -(struct file *file, char __user *buffer, size_t count, loff_t *ppos) > +static ssize_t wdm_read(struct file *file, char __user *buffer, > + size_t count, loff_t *ppos) > { > int rv, cntr; > int i = 0; > struct wdm_device *desc = file->private_data; > > + if (test_bit(WDM_DISCONNECTING, &desc->flags)) > + return -ENODEV; > > rv = mutex_lock_interruptible(&desc->rlock); /*concurrent reads */ > if (rv < 0) > return -ERESTARTSYS; > > + if (test_bit(WDM_DISCONNECTING, &desc->flags)) { > + rv = -ENODEV; > + goto err; > + } Why test before the lock if you test right after the lock? and what happens if the bit is set right _after_ you test this? thanks, greg k-h
