On Mon, Sep 25, 2017 at 6:26 AM, Kalle Valo [off-list ref] wrote:

Andrey Konovalov [off-list ref] writes:

quoted

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

On commit 6e80ecdddf4ea6f3cd84e83720f3d852e6624a68 (Sep 21).

==================================================================
BUG: KASAN: use-after-free in __run_timers+0xc0e/0xd40
Write of size 8 at addr ffff880069f701b8 by task swapper/0/0

CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.14.0-rc1-42311-g6e80ecdddf4e #234
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011

[...]

quoted

Allocated by task 1845:
 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
 kmem_cache_alloc_trace+0x11e/0x2d0 mm/slub.c:2772
 kmalloc ./include/linux/slab.h:493
 kzalloc ./include/linux/slab.h:666
 rsi_91x_init+0x98/0x510 drivers/net/wireless/rsi/rsi_91x_main.c:203
 rsi_probe+0xb6/0x13b0 drivers/net/wireless/rsi/rsi_91x_usb.c:665
 usb_probe_interface+0x35d/0x8e0 drivers/usb/core/driver.c:361

I'm curious about your setup. Apparently you are running syzkaller on
QEMU but what I don't understand is how the rsi device comes into the
picture. Did you have a rsi usb device connected to the virtual machine
or what? Or does syzkaller do some kind of magic here?

I use dummy_hcd and gadgetfs to connect random USB devices to the
kernel from a userspace application. This happens inside a QEMU
instance. This simplifies fuzzing, since everything is virtualized,
but the found bugs can be triggered on a real machine by connecting a
malicious USB device.

--
Kalle Valo

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