KASAN: use-after-free Read in dvb_usb_device_exit

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 9a33b369 usb-fuzzer: main usb gadget fuzzer driver
git tree: https://github.com/google/kasan/tree/usb-fuzzer
console output: https://syzkaller.appspot.com/x/log.txt?x=1643974b200000
kernel config: https://syzkaller.appspot.com/x/.config?x=23e37f59d94ddd15
dashboard link: https://syzkaller.appspot.com/bug?extid=26ec41e9f788b3eba396
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12f5efa7200000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1395a0f3200000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+26ec41...@syzkaller.appspotmail.com

dvb-usb: schedule remote query interval to 150 msecs.
dw2102: su3000_power_ctrl: 0, initialized 1
dvb-usb: TeVii S421 PCI successfully initialized and connected.
usb 1-1: USB disconnect, device number 2
==================================================================
BUG: KASAN: use-after-free in dvb_usb_device_exit+0xbb/0xd0
drivers/media/usb/dvb-usb/dvb-usb-init.c:294
Read of size 8 at addr ffff88809ec693d8 by task kworker/1:1/21

CPU: 1 PID: 21 Comm: kworker/1:1 Not tainted 5.1.0-rc4-319354-g9a33b36 #3
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+0xe8/0x16e lib/dump_stack.c:113
print_address_description+0x6c/0x236 mm/kasan/report.c:187
kasan_report.cold+0x1a/0x3c mm/kasan/report.c:317
dvb_usb_device_exit+0xbb/0xd0 drivers/media/usb/dvb-usb/dvb-usb-init.c:294
usb_unbind_interface+0x1c9/0x980 drivers/usb/core/driver.c:423
__device_release_driver drivers/base/dd.c:1082 [inline]
device_release_driver_internal+0x436/0x4f0 drivers/base/dd.c:1113
bus_remove_device+0x302/0x5c0 drivers/base/bus.c:556
device_del+0x467/0xb90 drivers/base/core.c:2269
usb_disable_device+0x242/0x790 drivers/usb/core/message.c:1235
usb_disconnect+0x298/0x870 drivers/usb/core/hub.c:2197
hub_port_connect drivers/usb/core/hub.c:4940 [inline]
hub_port_connect_change drivers/usb/core/hub.c:5204 [inline]
port_event drivers/usb/core/hub.c:5350 [inline]
hub_event+0xcd2/0x3b00 drivers/usb/core/hub.c:5432
process_one_work+0x90f/0x1580 kernel/workqueue.c:2269
process_scheduled_works kernel/workqueue.c:2331 [inline]
worker_thread+0x7b0/0xe20 kernel/workqueue.c:2417
kthread+0x313/0x420 kernel/kthread.c:253
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352

Allocated by task 21:
set_track mm/kasan/common.c:87 [inline]
__kasan_kmalloc mm/kasan/common.c:497 [inline]
__kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:470
slab_post_alloc_hook mm/slab.h:437 [inline]
slab_alloc_node mm/slub.c:2756 [inline]
slab_alloc mm/slub.c:2764 [inline]
__kmalloc_track_caller+0xf0/0x2c0 mm/slub.c:4342
kmemdup+0x23/0x50 mm/util.c:118
kmemdup include/linux/string.h:428 [inline]
dw2102_probe+0x62c/0xc50 drivers/media/usb/dvb-usb/dw2102.c:2375
usb_probe_interface+0x31d/0x820 drivers/usb/core/driver.c:361
really_probe+0x2da/0xb10 drivers/base/dd.c:509
driver_probe_device+0x21d/0x350 drivers/base/dd.c:671
__device_attach_driver+0x1d8/0x290 drivers/base/dd.c:778
bus_for_each_drv+0x163/0x1e0 drivers/base/bus.c:454
__device_attach+0x223/0x3a0 drivers/base/dd.c:844
bus_probe_device+0x1f1/0x2a0 drivers/base/bus.c:514
device_add+0xad2/0x16e0 drivers/base/core.c:2106
usb_set_configuration+0xdf7/0x1740 drivers/usb/core/message.c:2021
generic_probe+0xa2/0xda drivers/usb/core/generic.c:210
usb_probe_device+0xc0/0x150 drivers/usb/core/driver.c:266
really_probe+0x2da/0xb10 drivers/base/dd.c:509
driver_probe_device+0x21d/0x350 drivers/base/dd.c:671
__device_attach_driver+0x1d8/0x290 drivers/base/dd.c:778
bus_for_each_drv+0x163/0x1e0 drivers/base/bus.c:454
__device_attach+0x223/0x3a0 drivers/base/dd.c:844
bus_probe_device+0x1f1/0x2a0 drivers/base/bus.c:514
device_add+0xad2/0x16e0 drivers/base/core.c:2106
usb_new_device.cold+0x537/0xccf drivers/usb/core/hub.c:2534
hub_port_connect drivers/usb/core/hub.c:5089 [inline]
hub_port_connect_change drivers/usb/core/hub.c:5204 [inline]
port_event drivers/usb/core/hub.c:5350 [inline]
hub_event+0x138e/0x3b00 drivers/usb/core/hub.c:5432
process_one_work+0x90f/0x1580 kernel/workqueue.c:2269
worker_thread+0x9b/0xe20 kernel/workqueue.c:2415
kthread+0x313/0x420 kernel/kthread.c:253
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352

Freed by task 21:
set_track mm/kasan/common.c:87 [inline]
__kasan_slab_free+0x130/0x180 mm/kasan/common.c:459
slab_free_hook mm/slub.c:1429 [inline]
slab_free_freelist_hook+0x5e/0x140 mm/slub.c:1456
slab_free mm/slub.c:3003 [inline]
kfree+0xce/0x290 mm/slub.c:3958
dw2102_probe+0x876/0xc50 drivers/media/usb/dvb-usb/dw2102.c:2409
usb_probe_interface+0x31d/0x820 drivers/usb/core/driver.c:361
really_probe+0x2da/0xb10 drivers/base/dd.c:509
driver_probe_device+0x21d/0x350 drivers/base/dd.c:671
__device_attach_driver+0x1d8/0x290 drivers/base/dd.c:778
bus_for_each_drv+0x163/0x1e0 drivers/base/bus.c:454
__device_attach+0x223/0x3a0 drivers/base/dd.c:844
bus_probe_device+0x1f1/0x2a0 drivers/base/bus.c:514
device_add+0xad2/0x16e0 drivers/base/core.c:2106
usb_set_configuration+0xdf7/0x1740 drivers/usb/core/message.c:2021
generic_probe+0xa2/0xda drivers/usb/core/generic.c:210
usb_probe_device+0xc0/0x150 drivers/usb/core/driver.c:266
really_probe+0x2da/0xb10 drivers/base/dd.c:509
driver_probe_device+0x21d/0x350 drivers/base/dd.c:671
__device_attach_driver+0x1d8/0x290 drivers/base/dd.c:778
bus_for_each_drv+0x163/0x1e0 drivers/base/bus.c:454
__device_attach+0x223/0x3a0 drivers/base/dd.c:844
bus_probe_device+0x1f1/0x2a0 drivers/base/bus.c:514
device_add+0xad2/0x16e0 drivers/base/core.c:2106
usb_new_device.cold+0x537/0xccf drivers/usb/core/hub.c:2534
hub_port_connect drivers/usb/core/hub.c:5089 [inline]
hub_port_connect_change drivers/usb/core/hub.c:5204 [inline]
port_event drivers/usb/core/hub.c:5350 [inline]
hub_event+0x138e/0x3b00 drivers/usb/core/hub.c:5432
process_one_work+0x90f/0x1580 kernel/workqueue.c:2269
worker_thread+0x9b/0xe20 kernel/workqueue.c:2415
kthread+0x313/0x420 kernel/kthread.c:253
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352

The buggy address belongs to the object at ffff88809ec69100
which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 728 bytes inside of
4096-byte region [ffff88809ec69100, ffff88809ec6a100)
The buggy address belongs to the page:
page:ffffea00027b1a00 count:1 mapcount:0 mapping:ffff88812c3f4600 index:0x0
compound_mapcount: 0
flags: 0xfff00000010200(slab|head)
raw: 00fff00000010200 dead000000000100 dead000000000200 ffff88812c3f4600
raw: 0000000000000000 0000000000070007 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88809ec69280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88809ec69300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff88809ec69380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88809ec69400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88809ec69480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

[Oliver Neukum]

On Fr, 2019-04-12 at 04:46 -0700, syzbot wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: 9a33b369 usb-fuzzer: main usb gadget fuzzer driver
> git tree: https://github.com/google/kasan/tree/usb-fuzzer
> console output: https://syzkaller.appspot.com/x/log.txt?x=1643974b200000
> kernel config: https://syzkaller.appspot.com/x/.config?x=23e37f59d94ddd15
> dashboard link: https://syzkaller.appspot.com/bug?extid=26ec41e9f788b3eba396
> compiler: gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12f5efa7200000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1395a0f3200000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+26ec41...@syzkaller.appspotmail.com
>
> dvb-usb: schedule remote query interval to 150 msecs.
> dw2102: su3000_power_ctrl: 0, initialized 1
> dvb-usb: TeVii S421 PCI successfully initialized and connected.
> usb 1-1: USB disconnect, device number 2

Hi,

proposed fix. If nobody objects, I will submit it.

Regards
Oliver

From d6097d205ac61745334b79639d3b8b910ae66c71 Mon Sep 17 00:00:00 2001
From: Oliver Neukum <one...@suse.com>
Date: Mon, 15 Apr 2019 13:06:01 +0200
Subject: [PATCH] dvb: usb: fix use after free in dvb_usb_device_exit

dvb_usb_device_exit() frees and uses teh device name in that order
Fix by storing the name in a buffer before freeing it

Signed-off-by: Oliver Neukum <one...@suse.com>
Reported-by: syzbot+26ec41...@syzkaller.appspotmail.com
---
drivers/media/usb/dvb-usb/dvb-usb-init.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/media/usb/dvb-usb/dvb-usb-init.c b/drivers/media/usb/dvb-usb/dvb-usb-init.c
index 99951e02a880..2e1670cc3903 100644
--- a/drivers/media/usb/dvb-usb/dvb-usb-init.c
+++ b/drivers/media/usb/dvb-usb/dvb-usb-init.c
@@ -288,13 +288,18 @@ void dvb_usb_device_exit(struct usb_interface *intf)
{
struct dvb_usb_device *d = usb_get_intfdata(intf);
const char *name = "generic DVB-USB module";
+ char identifier[40];

usb_set_intfdata(intf, NULL);
if (d != NULL && d->desc != NULL) {
name = d->desc->name;
+ memcpy(identifier, name, 39);
+ identifier[39] = NULL;
dvb_usb_exit(d);
+ } else {
+ memcpy(identifier, name, 39);
}
- info("%s successfully deinitialized and disconnected.", name);
+ info("%s successfully deinitialized and disconnected.", identifier);

}
EXPORT_SYMBOL(dvb_usb_device_exit);
--
2.16.4

[Sergei Shtylyov]

Hello!

On 04/15/2019 02:12 PM, Oliver Neukum wrote:

[...]

> From d6097d205ac61745334b79639d3b8b910ae66c71 Mon Sep 17 00:00:00 2001
> From: Oliver Neukum <one...@suse.com>
> Date: Mon, 15 Apr 2019 13:06:01 +0200
> Subject: [PATCH] dvb: usb: fix use after free in dvb_usb_device_exit
>
> dvb_usb_device_exit() frees and uses teh device name in that order

s/teh/the/.

> Fix by storing the name in a buffer before freeing it
>
> Signed-off-by: Oliver Neukum <one...@suse.com>
> Reported-by: syzbot+26ec41...@syzkaller.appspotmail.com
> ---
> drivers/media/usb/dvb-usb/dvb-usb-init.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/media/usb/dvb-usb/dvb-usb-init.c b/drivers/media/usb/dvb-usb/dvb-usb-init.c
> index 99951e02a880..2e1670cc3903 100644
> --- a/drivers/media/usb/dvb-usb/dvb-usb-init.c
> +++ b/drivers/media/usb/dvb-usb/dvb-usb-init.c
> @@ -288,13 +288,18 @@ void dvb_usb_device_exit(struct usb_interface *intf)
> {
> struct dvb_usb_device *d = usb_get_intfdata(intf);
> const char *name = "generic DVB-USB module";
> + char identifier[40];
>
> usb_set_intfdata(intf, NULL);
> if (d != NULL && d->desc != NULL) {
> name = d->desc->name;
> + memcpy(identifier, name, 39);
> + identifier[39] = NULL;

NULL is for pointers, no?

> dvb_usb_exit(d);
> + } else {
> + memcpy(identifier, name, 39);
> }
> - info("%s successfully deinitialized and disconnected.", name);
> + info("%s successfully deinitialized and disconnected.", identifier);
>
> }
> EXPORT_SYMBOL(dvb_usb_device_exit);

MBR, Sergei

[Hans Verkuil]

Why not just move this to after the info()? You'll need to repeat the
'if' in that case, but that way there is no need to memcpy anything.

Regards,

Hans

[Oliver Neukum]

The info() would make the incorrect claim that something has been
freed. It looks to me like it exists to guarantee that you know that
nothing hung while freeing.

Regards
Oliver