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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Tue, 3 Dec 2019 07:29:23 +0100
Message-ID: <CACT4Y+apyc+q__suXWLGXVOEdhZhjTOHH3oXqo=Gpo6Hc=tdyw@mail.gmail.com>
Subject: Re: KASAN: use-after-free Read in slcan_open
To:     Oliver Hartkopp <socketcan@hartkopp.net>
Cc:     syzbot <syzbot+b5ec6fd05ab552a78532@syzkaller.appspotmail.com>,
        David Miller <davem@davemloft.net>, linux-can@vger.kernel.org,
        LKML <linux-kernel@vger.kernel.org>,
        Marc Kleine-Budde <mkl@pengutronix.de>,
        netdev <netdev@vger.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        wg@grandegger.com, Jouni Hogander <jouni.hogander@unikie.com>
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Sender: linux-kernel-owner@vger.kernel.org
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On Mon, Dec 2, 2019 at 10:28 PM Oliver Hartkopp <socketcan@hartkopp.net> wrote:
>
> 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.

#syz fix: slcan: Fix use-after-free Read in slcan_open

> 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:
> > 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
>
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