KASAN: use-after-free Read in service_outstanding_interrupt

KASAN: use-after-free Read in service_outstanding_interrupt

[syzbot]

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=108adf32900000
kernel config:  https://syzkaller.appspot.com/x/.config?x=72a84c46d0c668c
dashboard link: https://syzkaller.appspot.com/bug?extid=9e04e2df4a32fb661daf
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+9e04e2df4a32fb661daf@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in usb_submit_urb+0x10c4/0x13e0 drivers/usb/core/urb.c:368
Read of size 4 at addr ffff8881caa52018 by task syz-executor.3/13922

CPU: 1 PID: 13922 Comm: syz-executor.3 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
 usb_submit_urb+0x10c4/0x13e0 drivers/usb/core/urb.c:368
 service_outstanding_interrupt.part.0+0x5f/0xa0 drivers/usb/class/cdc-wdm.c:463
 service_outstanding_interrupt drivers/usb/class/cdc-wdm.c:458 [inline]
 wdm_read+0x9a0/0xbd0 drivers/usb/class/cdc-wdm.c:576
 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: 0033:0x45ce79
Code: 2d b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 fb b5 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f8d2099fc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00000000000252c0 RCX: 000000000045ce79
RDX: 00000000000000f2 RSI: 0000000020000100 RDI: 0000000000000003
RBP: 000000000118bf60 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118bf2c
R13: 00007ffd66f595ff R14: 00007f8d209a09c0 R15: 000000000118bf2c

Allocated by task 4524:
 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
 kmalloc include/linux/slab.h:555 [inline]
 kzalloc include/linux/slab.h:669 [inline]
 usb_alloc_dev+0x51/0xf67 drivers/usb/core/usb.c:582
 hub_port_connect drivers/usb/core/hub.c:5114 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5348 [inline]
 port_event drivers/usb/core/hub.c:5494 [inline]
 hub_event+0x1dff/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 5477:
 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
 device_release+0x71/0x200 drivers/base/core.c:1800
 kobject_cleanup lib/kobject.c:704 [inline]
 kobject_release lib/kobject.c:735 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x1c8/0x540 lib/kobject.c:752
 put_device+0x1b/0x30 drivers/base/core.c:3029
 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
 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

The buggy address belongs to the object at ffff8881caa52000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 24 bytes inside of
 2048-byte region [ffff8881caa52000, ffff8881caa52800)
The buggy address belongs to the page:
page:ffffea00072a9400 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 head:ffffea00072a9400 order:3 compound_mapcount:0 compound_pincount:0
flags: 0x200000000010200(slab|head)
raw: 0200000000010200 0000000000000000 0000000100000001 ffff8881da00c000
raw: 0000000000000000 0000000000080008 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8881caa51f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8881caa51f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8881caa52000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff8881caa52080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881caa52100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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Re: KASAN: use-after-free Read in service_outstanding_interrupt

[syzbot]

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@syzkaller.appspotmail.com

==================================================================
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
==================================================================

Re: KASAN: use-after-free Read in service_outstanding_interrupt

[Greg KH]

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@syzkaller.appspotmail.com
> > 
> > ==================================================================
> > 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

Re: KASAN: use-after-free Read in service_outstanding_interrupt

[Greg KH]

On Fri, Dec 18, 2020 at 06:01:34PM +0800, Hillf Danton wrote:
> On Fri, 18 Dec 2020 09:28:16 +0100 Greg KH wrote:
> >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@syzkaller.appspotmail.com
> >> > 
> >> > ==================================================================
> >> > 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?
> 
> Any test is supposed to make sense.

I do not understand.

I am trying to say, why do you even have the test outside of the lock as
that makes no sense?

> >and what happens if the bit is set right _after_ you test this?
> 
> Your question explains the above double test.

No it doesn't :)

> If we get desc->rlock and fail to test WDM_DISCONNECTING in the
> read path then we are safe because the same lock is acquired also
> in the disconnect path.

Then only check the bit _when_ the lock is held.  Otherwise it is a
pointless check.

thanks,

greg k-h

Re: KASAN: use-after-free Read in service_outstanding_interrupt

[Tetsuo Handa]

Hello, Oliver.

I guess that this is caused by not checking WDM_DISCONNECTING/WDM_RESETTING
before usb_submit_urb(), and below diff seems to avoid use-after-free for
the C reproducer syzbot has found.

Since service_outstanding_interrupt() is called from service_interrupt_work()
without holding desc->rlock, it is possible that kill_urbs() is called by
wdm_disconnect() when service_outstanding_interrupt() is preempted between
spin_unlock_irq(&desc->iuspin) and usb_submit_urb(), isn't it?
Therefore, we also need to make sure that kill_urbs(desc) is called after
cancel_work_sync(&desc->service_outs_intr) which waits for
service_interrupt_work() to return completed, don't we?

diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c
index 02d0cfd23bb2..508b1c3f8b73 100644
--- a/drivers/usb/class/cdc-wdm.c
+++ b/drivers/usb/class/cdc-wdm.c
@@ -465,13 +465,23 @@ static int service_outstanding_interrupt(struct wdm_device *desc)
 	if (!desc->resp_count || !--desc->resp_count)
 		goto out;
 
+	if (test_bit(WDM_DISCONNECTING, &desc->flags)) {
+		rv = -ENODEV;
+		goto out;
+	}
+	if (test_bit(WDM_RESETTING, &desc->flags)) {
+		rv = -EIO;
+		goto out;
+	}
+
 	set_bit(WDM_RESPONDING, &desc->flags);
 	spin_unlock_irq(&desc->iuspin);
 	rv = usb_submit_urb(desc->response, GFP_KERNEL);
 	spin_lock_irq(&desc->iuspin);
 	if (rv) {
-		dev_err(&desc->intf->dev,
-			"usb_submit_urb failed with result %d\n", rv);
+		if (!test_bit(WDM_DISCONNECTING, &desc->flags))
+			dev_err(&desc->intf->dev,
+				"usb_submit_urb failed with result %d\n", rv);
 
 		/* make sure the next notification trigger a submit */
 		clear_bit(WDM_RESPONDING, &desc->flags);
@@ -1027,9 +1037,9 @@ static void wdm_disconnect(struct usb_interface *intf)
 	wake_up_all(&desc->wait);
 	mutex_lock(&desc->rlock);
 	mutex_lock(&desc->wlock);
-	kill_urbs(desc);
 	cancel_work_sync(&desc->rxwork);
 	cancel_work_sync(&desc->service_outs_intr);
+	kill_urbs(desc);
 	mutex_unlock(&desc->wlock);
 	mutex_unlock(&desc->rlock);
 

[PATCH] USB: cdc-wdm: Fix use after free in service_outstanding_interrupt().

[Tetsuo Handa]

syzbot is reporting UAF at usb_submit_urb() [1], for
service_outstanding_interrupt() is not checking WDM_DISCONNECTING
before calling usb_submit_urb(). Close the race by doing same checks
wdm_read() does upon retry.

Also, while wdm_read() checks WDM_DISCONNECTING with desc->rlock held,
service_interrupt_work() does not hold desc->rlock. Thus, it is possible
that usb_submit_urb() is called from service_outstanding_interrupt() from
service_interrupt_work() after WDM_DISCONNECTING was set and kill_urbs()
 from wdm_disconnect() completed. Thus, move kill_urbs() in
wdm_disconnect() to after cancel_work_sync() (which makes sure that
service_interrupt_work() is no longer running) completed.

Although it seems to be safe to dereference desc->intf->dev in
service_outstanding_interrupt() even if WDM_DISCONNECTING was already set
because desc->rlock or cancel_work_sync() prevents wdm_disconnect() from
reaching list_del() before service_outstanding_interrupt() completes,
let's not emit error message if WDM_DISCONNECTING is set by
wdm_disconnect() while usb_submit_urb() is in progress.

[1] https://syzkaller.appspot.com/bug?extid=9e04e2df4a32fb661daf

Reported-by: syzbot <syzbot+9e04e2df4a32fb661daf@syzkaller.appspotmail.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
---
 drivers/usb/class/cdc-wdm.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c
index 02d0cfd23bb2..508b1c3f8b73 100644
--- a/drivers/usb/class/cdc-wdm.c
+++ b/drivers/usb/class/cdc-wdm.c
@@ -465,13 +465,23 @@ static int service_outstanding_interrupt(struct wdm_device *desc)
 	if (!desc->resp_count || !--desc->resp_count)
 		goto out;
 
+	if (test_bit(WDM_DISCONNECTING, &desc->flags)) {
+		rv = -ENODEV;
+		goto out;
+	}
+	if (test_bit(WDM_RESETTING, &desc->flags)) {
+		rv = -EIO;
+		goto out;
+	}
+
 	set_bit(WDM_RESPONDING, &desc->flags);
 	spin_unlock_irq(&desc->iuspin);
 	rv = usb_submit_urb(desc->response, GFP_KERNEL);
 	spin_lock_irq(&desc->iuspin);
 	if (rv) {
-		dev_err(&desc->intf->dev,
-			"usb_submit_urb failed with result %d\n", rv);
+		if (!test_bit(WDM_DISCONNECTING, &desc->flags))
+			dev_err(&desc->intf->dev,
+				"usb_submit_urb failed with result %d\n", rv);
 
 		/* make sure the next notification trigger a submit */
 		clear_bit(WDM_RESPONDING, &desc->flags);
@@ -1027,9 +1037,9 @@ static void wdm_disconnect(struct usb_interface *intf)
 	wake_up_all(&desc->wait);
 	mutex_lock(&desc->rlock);
 	mutex_lock(&desc->wlock);
-	kill_urbs(desc);
 	cancel_work_sync(&desc->rxwork);
 	cancel_work_sync(&desc->service_outs_intr);
+	kill_urbs(desc);
 	mutex_unlock(&desc->wlock);
 	mutex_unlock(&desc->rlock);
 
-- 
2.25.1

Re: [PATCH] USB: cdc-wdm: Fix use after free in service_outstanding_interrupt().

[Oliver Neukum]

Am Sonntag, den 20.12.2020, 00:25 +0900 schrieb Tetsuo Handa:
> syzbot is reporting UAF at usb_submit_urb() [1], for
> service_outstanding_interrupt() is not checking WDM_DISCONNECTING
> before calling usb_submit_urb(). Close the race by doing same checks
> wdm_read() does upon retry.

But wdm_read() does them with proper locking.

> Also, while wdm_read() checks WDM_DISCONNECTING with desc->rlock held,
> service_interrupt_work() does not hold desc->rlock. Thus, it is possible
> that usb_submit_urb() is called from service_outstanding_interrupt() from
> service_interrupt_work() after WDM_DISCONNECTING was set and kill_urbs()
>  from wdm_disconnect() completed. Thus, move kill_urbs() in
> wdm_disconnect() to after cancel_work_sync() (which makes sure that
> service_interrupt_work() is no longer running) completed.

That seems to be the right approach. You must prevent this helper
from being called in the first place.

	Regards
		Oliver

Re: KASAN: use-after-free Read in service_outstanding_interrupt

[Oliver Neukum]

Am Donnerstag, den 17.12.2020, 19:21 -0800 schrieb syzbot:
> 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@syzkaller.appspotmail.com

#syz test: https://github.com/google/kasan.git  5e60366d

From f51e3c5a202f3abc805edd64b21a68d29dd9d60e Mon Sep 17 00:00:00 2001
From: Oliver Neukum <oneukum@suse.com>
Date: Mon, 4 Jan 2021 17:26:33 +0100
Subject: [PATCH] cdc-wdm: poison URBs upon disconnect

We have a chicken and egg issue between interrupt and work.
This should break the cycle.

Signed-off-by: Oliver Neukum <oneukum@suse.com>
---
 drivers/usb/class/cdc-wdm.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c
index 02d0cfd23bb2..14eddda35280 100644
--- a/drivers/usb/class/cdc-wdm.c
+++ b/drivers/usb/class/cdc-wdm.c
@@ -324,9 +324,9 @@ static void wdm_int_callback(struct urb *urb)
 static void kill_urbs(struct wdm_device *desc)
 {
 	/* the order here is essential */
-	usb_kill_urb(desc->command);
-	usb_kill_urb(desc->validity);
-	usb_kill_urb(desc->response);
+	usb_poison_urb(desc->command);
+	usb_poison_urb(desc->validity);
+	usb_poison_urb(desc->response);
 }
 
 static void free_urbs(struct wdm_device *desc)
-- 
2.26.2

Re: KASAN: use-after-free Read in service_outstanding_interrupt

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: use-after-free Read in service_outstanding_interrupt

==================================================================
BUG: KASAN: use-after-free in usb_submit_urb+0x1210/0x1560 drivers/usb/core/urb.c:383
Read of size 4 at addr ffff888113e9f018 by task syz-executor.0/7799

CPU: 1 PID: 7799 Comm: syz-executor.0 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: 0033:0x45e149
Code: 0d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 db b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fcce8099c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045e149
RDX: 0000000000001000 RSI: 0000000020001000 RDI: 0000000000000004
RBP: 000000000119c068 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000119c034
R13: 00007fffc13967df R14: 00007fcce809a9c0 R15: 000000000119c034

Allocated by task 17:
 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 2183:
 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

Last potentially related work creation:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
 kasan_record_aux_stack+0xc0/0xf0 mm/kasan/generic.c:343
 insert_work+0x48/0x370 kernel/workqueue.c:1331
 __queue_work+0x5c3/0xf60 kernel/workqueue.c:1497
 queue_work_on+0xc7/0xd0 kernel/workqueue.c:1524
 kref_put include/linux/kref.h:65 [inline]
 tty_kref_put drivers/tty/tty_io.c:1493 [inline]
 release_tty+0x4e9/0x610 drivers/tty/tty_io.c:1530
 tty_release_struct+0xb4/0xe0 drivers/tty/tty_io.c:1629
 tty_release+0xc70/0x1210 drivers/tty/tty_io.c:1789
 __fput+0x288/0x920 fs/file_table.c:280
 task_work_run+0xdd/0x1a0 kernel/task_work.c:168
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:174 [inline]
 exit_to_user_mode_prepare+0x186/0x190 kernel/entry/common.c:201
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x19/0x50 kernel/entry/common.c:302
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

The buggy address belongs to the object at ffff888113e9f000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 24 bytes inside of
 2048-byte region [ffff888113e9f000, ffff888113e9f800)
The buggy address belongs to the page:
page:00000000e5a7bd64 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x113e98
head:00000000e5a7bd64 order:3 compound_mapcount:0 compound_pincount:0
flags: 0x200000000010200(slab|head)
raw: 0200000000010200 dead000000000100 dead000000000122 ffff888100042000
raw: 0000000000000000 0000000000080008 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888113e9ef00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888113e9ef80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888113e9f000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff888113e9f080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888113e9f100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


Tested on:

commit:         5e60366d Merge tag 'fallthrough-fixes-clang-5.11-rc1' of g..
git tree:       https://github.com/google/kasan.git
console output: https://syzkaller.appspot.com/x/log.txt?x=1755d077500000
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
patch:          https://syzkaller.appspot.com/x/patch.diff?x=15e05e57500000

回复: KASAN: use-after-free Read in service_outstanding_interrupt

[Zhang, Qiang]

________________________________________
发件人: Oliver Neukum <oneukum@suse.com>
发送时间: 2021年1月5日 0:28
收件人: syzbot; andreyknvl@google.com; gregkh@linuxfoundation.org; gustavoars@kernel.org; ingrassia@epigenesys.com; lee.jones@linaro.org; linux-kernel@vger.kernel.org; linux-usb@vger.kernel.org; penguin-kernel@I-love.SAKURA.ne.jp; syzkaller-bugs@googlegroups.com
主题: Re: KASAN: use-after-free Read in service_outstanding_interrupt

Am Donnerstag, den 17.12.2020, 19:21 -0800 schrieb syzbot:
> 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@syzkaller.appspotmail.com
>
>#syz test: https://github.com/google/kasan.git  5e60366d
>

 Hello Oliver 
 
 this use-after-free still exists，It can be seen from calltrace that it is 
 usb_device's object  has been released when disconnect,
 can add a reference count to usb_device's object to avoid this problem 
 
 diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c
index 508b1c3f8b73..001cb93da6bf 100644
--- a/drivers/usb/class/cdc-wdm.c
+++ b/drivers/usb/class/cdc-wdm.c
@@ -106,6 +106,7 @@ struct wdm_device {
 
        struct list_head        device_list;
        int                     (*manage_power)(struct usb_interface *, int);
+       struct usb_device       *usb_dev;
 };
 
 static struct usb_driver wdm_driver;
@@ -338,6 +339,7 @@ static void free_urbs(struct wdm_device *desc)
 
 static void cleanup(struct wdm_device *desc)
 {
+       usb_put_dev(desc->usb_dev);
        kfree(desc->sbuf);
        kfree(desc->inbuf);
        kfree(desc->orq);
@@ -855,6 +857,7 @@ static int wdm_create(struct usb_interface *intf, struct usb_endpoint_descripto
r
        desc->intf = intf;
        INIT_WORK(&desc->rxwork, wdm_rxwork);
        INIT_WORK(&desc->service_outs_intr, service_interrupt_work);
+       desc->usb_dev = usb_get_dev(interface_to_usbdev(intf));
 
        rv = -EINVAL;
        if (!usb_endpoint_is_int_in(ep))




>From f51e3c5a202f3abc805edd64b21a68d29dd9d60e Mon Sep 17 >00:00:00 2001
>From: Oliver Neukum <oneukum@suse.com>
>Date: Mon, 4 Jan 2021 17:26:33 +0100
>Subject: [PATCH] cdc-wdm: poison URBs upon disconnect
>
>We have a chicken and egg issue between interrupt and work.
>This should break the cycle.
>
>Signed-off-by: Oliver Neukum <oneukum@suse.com>
>---
>drivers/usb/class/cdc-wdm.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
>diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc->wdm.c
>index 02d0cfd23bb2..14eddda35280 100644
>--- a/drivers/usb/class/cdc-wdm.c
>+++ b/drivers/usb/class/cdc-wdm.c
>@@ -324,9 +324,9 @@ static void wdm_int_callback(struct urb *urb)
>static void kill_urbs(struct wdm_device *desc)
> {
>       /* the order here is essential */
>-       usb_kill_urb(desc->command);
>-       usb_kill_urb(desc->validity);
>-       usb_kill_urb(desc->response);
>+       usb_poison_urb(desc->command);
>+       usb_poison_urb(desc->validity);
>+       usb_poison_urb(desc->response);
> }
>
> static void free_urbs(struct wdm_device *desc)
>--
>2.26.2

Re: 回复: KASAN: use-after-free Read in service_outstanding_interrupt

[Oliver Neukum]

Am Dienstag, den 05.01.2021, 04:50 +0000 schrieb Zhang, Qiang:
> 
> ________________________________________
> 发件人: Oliver Neukum <oneukum@suse.com>
> 发送时间: 2021年1月5日 0:28
> 收件人: syzbot; andreyknvl@google.com; gregkh@linuxfoundation.org; gustavoars@kernel.org; ingrassia@epigenesys.com; lee.jones@linaro.org; linux-kernel@vger.kernel.org; linux-usb@vger.kernel.org; penguin-kernel@I-love.SAKURA.ne.jp; syzkaller-bugs@googlegroups.com
> 主题: Re: KASAN: use-after-free Read in service_outstanding_interrupt
> 
> Am Donnerstag, den 17.12.2020, 19:21 -0800 schrieb syzbot:
> > 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@syzkaller.appspotmail.com
> > 
> > #syz test: https://github.com/google/kasan.git  5e60366d
> > 
> 
>  Hello Oliver 
>  
>  this use-after-free still exists，It can be seen from calltrace that it is 
>  usb_device's object  has been released when disconnect,
>  can add a reference count to usb_device's object to avoid this problem 

Hi,

thanks for your analysis. I think you are correct in your analysis, but
I am afraid your fix is not correct. The driver is submitting an URB
to a disconnected device. Your fix would prevent a crash, which is
definitely good, but we still cannot do that, because the device may
be owned by another driver or usbfs at that time.

	Regards
		Oliver