usb/core: slab-out-of-bounds in usb_set_configuration

[Andrey Konovalov]

Hi!

I've got the following crash while fuzzing the kernel with syzkaller.

On commit ebb2c2437d8008d46796902ff390653822af6cc4 (Sep 18).

It seems there's no proper size check of a
USB_DT_INTERFACE_ASSOCIATION descriptor. It's only checked that the
size is >= 2 in usb_parse_configuration(), so find_iad() might do
out-of-bounds access to intf_assoc->bInterfaceCount.

gadgetfs: bound to dummy_udc driver
usb 1-1: new full-speed USB device number 2 using dummy_hcd
gadgetfs: connected
gadgetfs: disconnected
gadgetfs: connected
usb 1-1: config 1 interface 0 altsetting 0 has an invalid endpoint
with address 0x0, skipping
usb 1-1: New USB device found, idVendor=0020, idProduct=410e
usb 1-1: New USB device strings: Mfr=0, Product=8, SerialNumber=3
usb 1-1: Product: a
usb 1-1: SerialNumber: a
==================================================================
BUG: KASAN: slab-out-of-bounds in usb_set_configuration+0x1859/0x1870
Read of size 1 at addr ffff88006a9d00de by task kworker/0:2/1260

CPU: 0 PID: 1260 Comm: kworker/0:2 Not tainted
4.14.0-rc1-42251-gebb2c2437d80 #169
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Workqueue: usb_hub_wq hub_event
Call Trace:
__dump_stack lib/dump_stack.c:16
dump_stack+0x292/0x395 lib/dump_stack.c:52
print_address_description+0x78/0x280 mm/kasan/report.c:252
kasan_report_error mm/kasan/report.c:351
kasan_report+0x22f/0x340 mm/kasan/report.c:409
__asan_report_load1_noabort+0x19/0x20 mm/kasan/report.c:427
find_iad drivers/usb/core/message.c:1644
usb_set_configuration+0x1859/0x1870 drivers/usb/core/message.c:1855
generic_probe+0x73/0xe0 drivers/usb/core/generic.c:174
usb_probe_device+0xaf/0xe0 drivers/usb/core/driver.c:266
really_probe drivers/base/dd.c:413
driver_probe_device+0x610/0xa00 drivers/base/dd.c:557
__device_attach_driver+0x230/0x290 drivers/base/dd.c:653
bus_for_each_drv+0x161/0x210 drivers/base/bus.c:463
__device_attach+0x26e/0x3d0 drivers/base/dd.c:710
device_initial_probe+0x1f/0x30 drivers/base/dd.c:757
bus_probe_device+0x1eb/0x290 drivers/base/bus.c:523
device_add+0xd0b/0x1660 drivers/base/core.c:1835
usb_new_device+0x7b8/0x1020 drivers/usb/core/hub.c:2457
hub_port_connect drivers/usb/core/hub.c:4903
hub_port_connect_change drivers/usb/core/hub.c:5009
port_event drivers/usb/core/hub.c:5115
hub_event+0x194d/0x3740 drivers/usb/core/hub.c:5195
process_one_work+0xc7f/0x1db0 kernel/workqueue.c:2119
worker_thread+0x221/0x1850 kernel/workqueue.c:2253
kthread+0x3a1/0x470 kernel/kthread.c:231
ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431

Allocated by task 1260:
save_stack_trace+0x1b/0x20 arch/x86/kernel/stacktrace.c:59
save_stack+0x43/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459
kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
__kmalloc+0x14e/0x310 mm/slub.c:3782
kmalloc ./include/linux/slab.h:498
usb_get_configuration+0x372/0x2a60 drivers/usb/core/config.c:848
usb_enumerate_device drivers/usb/core/hub.c:2290
usb_new_device+0xaae/0x1020 drivers/usb/core/hub.c:2426
hub_port_connect drivers/usb/core/hub.c:4903
hub_port_connect_change drivers/usb/core/hub.c:5009
port_event drivers/usb/core/hub.c:5115
hub_event+0x194d/0x3740 drivers/usb/core/hub.c:5195
process_one_work+0xc7f/0x1db0 kernel/workqueue.c:2119
worker_thread+0x221/0x1850 kernel/workqueue.c:2253
kthread+0x3a1/0x470 kernel/kthread.c:231
ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431

Freed by task 2870:
save_stack_trace+0x1b/0x20 arch/x86/kernel/stacktrace.c:59
save_stack+0x43/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459
kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:524
slab_free_hook mm/slub.c:1390
slab_free_freelist_hook mm/slub.c:1412
slab_free mm/slub.c:2988
kfree+0xf6/0x2f0 mm/slub.c:3919
load_elf_binary+0x39c2/0x4fa0 fs/binfmt_elf.c:1087
search_binary_handler+0x146/0x480 fs/exec.c:1634
exec_binprm fs/exec.c:1676
do_execveat_common.isra.31+0x16d2/0x2200 fs/exec.c:1798
do_execve fs/exec.c:1842
SYSC_execve fs/exec.c:1923
SyS_execve+0x3e/0x50 fs/exec.c:1918
do_syscall_64+0x2c5/0x830 arch/x86/entry/common.c:287
return_from_SYSCALL_64+0x0/0x7a arch/x86/entry/entry_64.S:245

The buggy address belongs to the object at ffff88006a9d00c0
which belongs to the cache kmalloc-32 of size 32
The buggy address is located 30 bytes inside of
32-byte region [ffff88006a9d00c0, ffff88006a9d00e0)
The buggy address belongs to the page:
page:ffffea0001aa7400 count:1 mapcount:0 mapping: (null)
index:0xffff88006a9d05a0
flags: 0x100000000000100(slab)
raw: 0100000000000100 0000000000000000 ffff88006a9d05a0 0000000180550054
raw: ffffea000193fa00 0000001400000014 ffff88006c403980 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88006a9cff80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88006a9d0000: fb fb fb fb fc fc fb fb fb fb fc fc fb fb fb fb
>ffff88006a9d0080: fc fc fb fb fb fb fc fc 00 00 00 05 fc fc fb fb
^
ffff88006a9d0100: fb fb fc fc fb fb fb fb fc fc fb fb fb fb fc fc
ffff88006a9d0180: 00 00 00 00 fc fc 00 00 00 00 fc fc fb fb fb fb
==================================================================

[Greg Kroah-Hartman]

On Mon, Sep 18, 2017 at 07:22:24PM +0200, Andrey Konovalov wrote:
> Hi!
>
> I've got the following crash while fuzzing the kernel with syzkaller.
>
> On commit ebb2c2437d8008d46796902ff390653822af6cc4 (Sep 18).
>
> It seems there's no proper size check of a
> USB_DT_INTERFACE_ASSOCIATION descriptor. It's only checked that the
> size is >= 2 in usb_parse_configuration(), so find_iad() might do
> out-of-bounds access to intf_assoc->bInterfaceCount.

Ah, nice catch!

Does the patch below fix this?

thanks,

greg k-h

---------------

diff --git a/drivers/usb/core/config.c b/drivers/usb/core/config.c
index 4be52c602e9b..a3dbac1938ec 100644
--- a/drivers/usb/core/config.c
+++ b/drivers/usb/core/config.c
@@ -643,15 +643,23 @@ static int usb_parse_configuration(struct usb_device *dev, int cfgidx,

} else if (header->bDescriptorType ==
USB_DT_INTERFACE_ASSOCIATION) {
+ struct usb_interface_assoc_descriptor *d;
+
+ d = (struct usb_interface_assoc_descriptor *)header;
+ if (d->bLength < USB_DT_INTERFACE_ASSOCIATION_SIZE) {
+ dev_warn(ddev,
+ "config %d has an invalid interface association descriptor of length %d, skipping\n",
+ cfgno, d->bLength);
+ continue;
+ }
+
if (iad_num == USB_MAXIADS) {
dev_warn(ddev, "found more Interface "
"Association Descriptors "
"than allocated for in "
"configuration %d\n", cfgno);
} else {
- config->intf_assoc[iad_num] =
- (struct usb_interface_assoc_descriptor
- *)header;
+ config->intf_assoc[iad_num] = d;
iad_num++;
}

diff --git a/include/uapi/linux/usb/ch9.h b/include/uapi/linux/usb/ch9.h
index ce1169af39d7..2a5d63040a0b 100644
--- a/include/uapi/linux/usb/ch9.h
+++ b/include/uapi/linux/usb/ch9.h
@@ -780,6 +780,7 @@ struct usb_interface_assoc_descriptor {
__u8 iFunction;
} __attribute__ ((packed));

+#define USB_DT_INTERFACE_ASSOCIATION_SIZE 8

/*-------------------------------------------------------------------------*/

[Andrey Konovalov]

On Mon, Sep 18, 2017 at 8:50 PM, Greg Kroah-Hartman
<gre...@linuxfoundation.org> wrote:
> On Mon, Sep 18, 2017 at 07:22:24PM +0200, Andrey Konovalov wrote:
>> Hi!
>>
>> I've got the following crash while fuzzing the kernel with syzkaller.
>>
>> On commit ebb2c2437d8008d46796902ff390653822af6cc4 (Sep 18).
>>
>> It seems there's no proper size check of a
>> USB_DT_INTERFACE_ASSOCIATION descriptor. It's only checked that the
>> size is >= 2 in usb_parse_configuration(), so find_iad() might do
>> out-of-bounds access to intf_assoc->bInterfaceCount.
>
> Ah, nice catch!
>
> Does the patch below fix this?

Hi Greg,

I believe it does and the bug is no longer triggered with the
reproducer that I have.

Tested-by: Andrey Konovalov <andre...@google.com>

Thanks!

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[Greg Kroah-Hartman]

On Tue, Sep 19, 2017 at 01:54:57PM +0200, Andrey Konovalov wrote:
> On Mon, Sep 18, 2017 at 8:50 PM, Greg Kroah-Hartman
> <gre...@linuxfoundation.org> wrote:
> > On Mon, Sep 18, 2017 at 07:22:24PM +0200, Andrey Konovalov wrote:
> >> Hi!
> >>
> >> I've got the following crash while fuzzing the kernel with syzkaller.
> >>
> >> On commit ebb2c2437d8008d46796902ff390653822af6cc4 (Sep 18).
> >>
> >> It seems there's no proper size check of a
> >> USB_DT_INTERFACE_ASSOCIATION descriptor. It's only checked that the
> >> size is >= 2 in usb_parse_configuration(), so find_iad() might do
> >> out-of-bounds access to intf_assoc->bInterfaceCount.
> >
> > Ah, nice catch!
> >
> > Does the patch below fix this?
>
> Hi Greg,
>
> I believe it does and the bug is no longer triggered with the
> reproducer that I have.
>
> Tested-by: Andrey Konovalov <andre...@google.com>

Thanks for testing, I'll go queue this up.

greg k-h