Date:   Mon, 9 Mar 2020 16:23:40 +0100
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     syzbot <syzbot+e8fe6fd37e640743df98@...kaller.appspotmail.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, linux-media@...r.kernel.org,
        USB list <linux-usb@...r.kernel.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>
Subject: Re: KASAN: use-after-free Read in em28xx_init_extension

On Mon, Sep 23, 2019 at 4:31 PM syzbot
<syzbot+e8fe6fd37e640743df98@...kaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    e0bd8d79 usb-fuzzer: main usb gadget fuzzer driver
> git tree:       https://github.com/google/kasan.git usb-fuzzer
> console output: https://syzkaller.appspot.com/x/log.txt?x=114d95ad600000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=8847e5384a16f66a
> dashboard link: https://syzkaller.appspot.com/bug?extid=e8fe6fd37e640743df98
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1692f991600000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=145d05b1600000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+e8fe6fd37e640743df98@...kaller.appspotmail.com
>
> em28xx 1-1:0.240: Audio interface 240 found (Vendor Class)
> em28xx 1-1:0.240: unknown em28xx chip ID (0)
> em28xx 1-1:0.240: Config register raw data: 0xfffffffb
> em28xx 1-1:0.240: AC97 chip type couldn't be determined
> em28xx 1-1:0.240: No AC97 audio processor
> ==================================================================
> BUG: KASAN: use-after-free in __list_add_valid+0xd8/0xf0 lib/list_debug.c:26
> Read of size 8 at addr ffff8881d31d0240 by task kworker/1:1/21
>
> CPU: 1 PID: 21 Comm: kworker/1:1 Not tainted 5.3.0+ #0
> 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+0xca/0x13e lib/dump_stack.c:113
>   print_address_description+0x6a/0x32c mm/kasan/report.c:351
>   __kasan_report.cold+0x1a/0x33 mm/kasan/report.c:482
>   kasan_report+0xe/0x12 mm/kasan/common.c:618
>   __list_add_valid+0xd8/0xf0 lib/list_debug.c:26
>   __list_add include/linux/list.h:60 [inline]
>   list_add_tail include/linux/list.h:93 [inline]
>   em28xx_init_extension+0x44/0x1f0
> drivers/media/usb/em28xx/em28xx-core.c:1125
>   em28xx_init_dev.isra.0+0xa7b/0x15d8
> drivers/media/usb/em28xx/em28xx-cards.c:3520
>   em28xx_usb_probe.cold+0xcac/0x2516
> drivers/media/usb/em28xx/em28xx-cards.c:3869
>   usb_probe_interface+0x305/0x7a0 drivers/usb/core/driver.c:361
>   really_probe+0x281/0x6d0 drivers/base/dd.c:548
>   driver_probe_device+0x101/0x1b0 drivers/base/dd.c:721
>   __device_attach_driver+0x1c2/0x220 drivers/base/dd.c:828
>   bus_for_each_drv+0x162/0x1e0 drivers/base/bus.c:430
>   __device_attach+0x217/0x360 drivers/base/dd.c:894
>   bus_probe_device+0x1e4/0x290 drivers/base/bus.c:490
>   device_add+0xae6/0x16f0 drivers/base/core.c:2201
>   usb_set_configuration+0xdf6/0x1670 drivers/usb/core/message.c:2023
>   generic_probe+0x9d/0xd5 drivers/usb/core/generic.c:210
>   usb_probe_device+0x99/0x100 drivers/usb/core/driver.c:266
>   really_probe+0x281/0x6d0 drivers/base/dd.c:548
>   driver_probe_device+0x101/0x1b0 drivers/base/dd.c:721
>   __device_attach_driver+0x1c2/0x220 drivers/base/dd.c:828
>   bus_for_each_drv+0x162/0x1e0 drivers/base/bus.c:430
>   __device_attach+0x217/0x360 drivers/base/dd.c:894
>   bus_probe_device+0x1e4/0x290 drivers/base/bus.c:490
>   device_add+0xae6/0x16f0 drivers/base/core.c:2201
>   usb_new_device.cold+0x6a4/0xe79 drivers/usb/core/hub.c:2536
>   hub_port_connect drivers/usb/core/hub.c:5098 [inline]
>   hub_port_connect_change drivers/usb/core/hub.c:5213 [inline]
>   port_event drivers/usb/core/hub.c:5359 [inline]
>   hub_event+0x1b5c/0x3640 drivers/usb/core/hub.c:5441
>   process_one_work+0x92b/0x1530 kernel/workqueue.c:2269
>   process_scheduled_works kernel/workqueue.c:2331 [inline]
>   worker_thread+0x7ab/0xe20 kernel/workqueue.c:2417
>   kthread+0x318/0x420 kernel/kthread.c:255
>   ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
>
> Allocated by task 238:
>   save_stack+0x1b/0x80 mm/kasan/common.c:69
>   set_track mm/kasan/common.c:77 [inline]
>   __kasan_kmalloc mm/kasan/common.c:493 [inline]
>   __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:466
>   slab_post_alloc_hook mm/slab.h:520 [inline]
>   slab_alloc_node mm/slub.c:2770 [inline]
>   slab_alloc mm/slub.c:2778 [inline]
>   kmem_cache_alloc+0xd6/0x2d0 mm/slub.c:2783
>   shmem_alloc_inode+0x18/0x40 mm/shmem.c:3630
>   alloc_inode+0x61/0x1e0 fs/inode.c:227
>   new_inode_pseudo+0x14/0xe0 fs/inode.c:916
>   new_inode+0x1b/0x40 fs/inode.c:945
>   shmem_get_inode+0x84/0x7e0 mm/shmem.c:2228
>   shmem_mknod+0x5a/0x1f0 mm/shmem.c:2864
>   lookup_open+0x119a/0x18d0 fs/namei.c:3224
>   do_last fs/namei.c:3314 [inline]
>   path_openat+0x1045/0x3f50 fs/namei.c:3525
>   do_filp_open+0x1a1/0x280 fs/namei.c:3555
>   do_sys_open+0x3c0/0x580 fs/open.c:1089
>   do_syscall_64+0xb7/0x580 arch/x86/entry/common.c:290
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> Freed by task 0:
>   save_stack+0x1b/0x80 mm/kasan/common.c:69
>   set_track mm/kasan/common.c:77 [inline]
>   __kasan_slab_free+0x130/0x180 mm/kasan/common.c:455
>   slab_free_hook mm/slub.c:1423 [inline]
>   slab_free_freelist_hook mm/slub.c:1474 [inline]
>   slab_free mm/slub.c:3016 [inline]
>   kmem_cache_free+0xb9/0x380 mm/slub.c:3032
>   i_callback+0x3f/0x70 fs/inode.c:216
>   __rcu_reclaim kernel/rcu/rcu.h:222 [inline]
>   rcu_do_batch kernel/rcu/tree.c:2157 [inline]
>   rcu_core+0x630/0x1ca0 kernel/rcu/tree.c:2377
>   __do_softirq+0x221/0x912 kernel/softirq.c:292
>
> The buggy address belongs to the object at ffff8881d31d0000
>   which belongs to the cache shmem_inode_cache of size 1184
> The buggy address is located 576 bytes inside of
>   1184-byte region [ffff8881d31d0000, ffff8881d31d04a0)
> The buggy address belongs to the page:
> page:ffffea00074c7400 refcount:1 mapcount:0 mapping:ffff8881da115180
> index:0x0 compound_mapcount: 0
> flags: 0x200000000010200(slab|head)
> raw: 0200000000010200 dead000000000100 dead000000000122 ffff8881da115180
> raw: 0000000000000000 00000000800c000c 00000001ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>   ffff8881d31d0100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>   ffff8881d31d0180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > ffff8881d31d0200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>                                             ^
>   ffff8881d31d0280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>   ffff8881d31d0300: 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 syzkaller@...glegroups.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

#syz dup: BUG: corrupted list in em28xx_init_extension

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