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Subject: Re: KASAN: use-after-free Read in slcan_open
To:     syzbot <syzbot+b5ec6fd05ab552a78532@syzkaller.appspotmail.com>,
        davem@davemloft.net, linux-can@vger.kernel.org,
        linux-kernel@vger.kernel.org, mkl@pengutronix.de,
        netdev@vger.kernel.org, syzkaller-bugs@googlegroups.com,
        wg@grandegger.com, Jouni Hogander <jouni.hogander@unikie.com>
References: <0000000000000e4f720598bb95f8@google.com>
From:   Oliver Hartkopp <socketcan@hartkopp.net>
Message-ID: <09ad00de-c082-3c69-5b81-ceae5e9cd3c9@hartkopp.net>
Date:   Mon, 2 Dec 2019 22:28:19 +0100
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This issue has already been addressed by Jouni Hogander here:

https://marc.info/?l=linux-can&m=157483684128186

The patch is waiting for upstream via linux-can tree.

Regards,
Oliver

On 02/12/2019 18.05, syzbot wrote:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    32ef9553 Merge tag 'fsnotify_for_v5.5-rc1' of 
> git://git.ke..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=12a48e9ce00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=ff560c3de405258c
> dashboard link: 
> https://syzkaller.appspot.com/bug?extid=b5ec6fd05ab552a78532
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12943882e00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10562f86e00000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+b5ec6fd05ab552a78532@syzkaller.appspotmail.com
> 
> ==================================================================
> BUG: KASAN: use-after-free in slc_sync drivers/net/can/slcan.c:504 [inline]
> BUG: KASAN: use-after-free in slcan_open+0x8a1/0x9e0 
> drivers/net/can/slcan.c:579
> Read of size 8 at addr ffff88809a6e0b88 by task syz-executor961/9030
> 
> CPU: 1 PID: 9030 Comm: syz-executor961 Not tainted 5.4.0-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+0x197/0x210 lib/dump_stack.c:118
>   print_address_description.constprop.0.cold+0xd4/0x30b 
> mm/kasan/report.c:374
>   __kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506
>   kasan_report+0x12/0x20 mm/kasan/common.c:634
>   __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:132
>   slc_sync drivers/net/can/slcan.c:504 [inline]
>   slcan_open+0x8a1/0x9e0 drivers/net/can/slcan.c:579
>   tty_ldisc_open.isra.0+0xa3/0x110 drivers/tty/tty_ldisc.c:469
>   tty_set_ldisc+0x30e/0x6b0 drivers/tty/tty_ldisc.c:596
>   tiocsetd drivers/tty/tty_io.c:2334 [inline]
>   tty_ioctl+0xe8d/0x14f0 drivers/tty/tty_io.c:2594
>   vfs_ioctl fs/ioctl.c:46 [inline]
>   file_ioctl fs/ioctl.c:509 [inline]
>   do_vfs_ioctl+0xdb6/0x13e0 fs/ioctl.c:696
>   ksys_ioctl+0xab/0xd0 fs/ioctl.c:713
>   __do_sys_ioctl fs/ioctl.c:720 [inline]
>   __se_sys_ioctl fs/ioctl.c:718 [inline]
>   __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
>   do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x4429e9
> Code: e8 dc 02 03 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 1b 0a fc ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007ffc7db87168 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00000000004429e9
> RDX: 00000000200000c0 RSI: 0000000000005423 RDI: 0000000000000003
> RBP: 0000000000000000 R08: 0000000000000002 R09: 0000000000003031
> R10: 0000000000000000 R11: 0000000000000246 R12: ffffffffffffffff
> R13: 0000000000000004 R14: 00007ffc7db871dc R15: 0000000000000000
> 
> Allocated by task 9029:
>   save_stack+0x23/0x90 mm/kasan/common.c:69
>   set_track mm/kasan/common.c:77 [inline]
>   __kasan_kmalloc mm/kasan/common.c:510 [inline]
>   __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:483
>   kasan_kmalloc+0x9/0x10 mm/kasan/common.c:524
>   __do_kmalloc_node mm/slab.c:3615 [inline]
>   __kmalloc_node+0x4e/0x70 mm/slab.c:3622
>   kmalloc_node include/linux/slab.h:599 [inline]
>   kvmalloc_node+0xbd/0x100 mm/util.c:564
>   kvmalloc include/linux/mm.h:670 [inline]
>   kvzalloc include/linux/mm.h:678 [inline]
>   alloc_netdev_mqs+0x98/0xde0 net/core/dev.c:9730
>   slc_alloc drivers/net/can/slcan.c:533 [inline]
>   slcan_open+0x32d/0x9e0 drivers/net/can/slcan.c:590
>   tty_ldisc_open.isra.0+0xa3/0x110 drivers/tty/tty_ldisc.c:469
>   tty_set_ldisc+0x30e/0x6b0 drivers/tty/tty_ldisc.c:596
>   tiocsetd drivers/tty/tty_io.c:2334 [inline]
>   tty_ioctl+0xe8d/0x14f0 drivers/tty/tty_io.c:2594
>   vfs_ioctl fs/ioctl.c:46 [inline]
>   file_ioctl fs/ioctl.c:509 [inline]
>   do_vfs_ioctl+0xdb6/0x13e0 fs/ioctl.c:696
>   ksys_ioctl+0xab/0xd0 fs/ioctl.c:713
>   __do_sys_ioctl fs/ioctl.c:720 [inline]
>   __se_sys_ioctl fs/ioctl.c:718 [inline]
>   __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
>   do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> Freed by task 9029:
>   save_stack+0x23/0x90 mm/kasan/common.c:69
>   set_track mm/kasan/common.c:77 [inline]
>   kasan_set_free_info mm/kasan/common.c:332 [inline]
>   __kasan_slab_free+0x102/0x150 mm/kasan/common.c:471
>   kasan_slab_free+0xe/0x10 mm/kasan/common.c:480
>   __cache_free mm/slab.c:3425 [inline]
>   kfree+0x10a/0x2c0 mm/slab.c:3756
>   kvfree+0x61/0x70 mm/util.c:593
>   netdev_freemem net/core/dev.c:9684 [inline]
>   free_netdev+0x3c0/0x470 net/core/dev.c:9839
>   slcan_open+0x848/0x9e0 drivers/net/can/slcan.c:620
>   tty_ldisc_open.isra.0+0xa3/0x110 drivers/tty/tty_ldisc.c:469
>   tty_set_ldisc+0x30e/0x6b0 drivers/tty/tty_ldisc.c:596
>   tiocsetd drivers/tty/tty_io.c:2334 [inline]
>   tty_ioctl+0xe8d/0x14f0 drivers/tty/tty_io.c:2594
>   vfs_ioctl fs/ioctl.c:46 [inline]
>   file_ioctl fs/ioctl.c:509 [inline]
>   do_vfs_ioctl+0xdb6/0x13e0 fs/ioctl.c:696
>   ksys_ioctl+0xab/0xd0 fs/ioctl.c:713
>   __do_sys_ioctl fs/ioctl.c:720 [inline]
>   __se_sys_ioctl fs/ioctl.c:718 [inline]
>   __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
>   do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> The buggy address belongs to the object at ffff88809a6e0000
>   which belongs to the cache kmalloc-32k of size 32768
> The buggy address is located 2952 bytes inside of
>   32768-byte region [ffff88809a6e0000, ffff88809a6e8000)
> The buggy address belongs to the page:
> page:ffffea000269b800 refcount:1 mapcount:0 mapping:ffff8880aa402540 
> index:0x0 compound_mapcount: 0
> raw: 00fffe0000010200 ffffea000244d008 ffff8880aa401d48 ffff8880aa402540
> raw: 0000000000000000 ffff88809a6e0000 0000000100000001 0000000000000000
> page dumped because: kasan: bad access detected
> 
> Memory state around the buggy address:
>   ffff88809a6e0a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>   ffff88809a6e0b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>> ffff88809a6e0b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>                        ^
>   ffff88809a6e0c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>   ffff88809a6e0c80: 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@googlegroups.com.
> 
> syzbot will keep track of this bug report. See:
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> syzbot can test patches for this bug, for details see:
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