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Subject: Re: UBSAN: Undefined behaviour in net/can/bcm.c
To:     Kyungtae Kim <kt0755@gmail.com>
Cc:     davem@davemloft.net, Arnd Bergmann <arnd@arndb.de>,
        mkl@pengutronix.de, Byoungyoung Lee <lifeasageek@gmail.com>,
        DaeRyong Jeong <threeearcat@gmail.com>,
        syzkaller@googlegroups.com, linux-can@vger.kernel.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
References: <CAEAjamvf8LzpRauFhxeh-EGY_ttqeds6_UQwikc5sm7ORKdjjw@mail.gmail.com>
 <c3a95ad5-5eae-6392-f263-9f05e7f51333@hartkopp.net>
 <CAEAjamsw9uu-VwHtREqetCsQBrF4B_Hy87xxsZRhAbHUOvzF4w@mail.gmail.com>
From:   Oliver Hartkopp <socketcan@hartkopp.net>
Message-ID: <7436eb01-c022-aadc-0d53-b23515ea42aa@hartkopp.net>
Date:   Sat, 12 Jan 2019 22:25:41 +0100
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On 1/12/19 10:03 PM, Kyungtae Kim wrote:
> On Sat, Jan 12, 2019 at 3:02 PM Oliver Hartkopp <socketcan@hartkopp.net> wrote:
>>
>> So there could potentially be some other users of timeval_to_ktime()
>> that might have the same issue.
>>
> 
> The following would be the one related.

Yes - it is also in bcm_rx_setup(). Same issue can potentially occur in 
bcm_tx_setup().

Will send a patch for testing in a minute.

Many thanks,
Oliver

> 
> =========================================
> UBSAN: Undefined behaviour in ./include/linux/ktime.h:42:14
> signed integer overflow:
> -3428892174463270912 * 1000000000 cannot be represented in type 'long int'
> CPU: 0 PID: 7024 Comm: syz-executor6 Not tainted 4.19.13 #1
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
> Call Trace:
>   __dump_stack lib/dump_stack.c:77 [inline]
>   dump_stack+0xd2/0x148 lib/dump_stack.c:113
>   ubsan_epilogue+0x12/0x94 lib/ubsan.c:159
>   handle_overflow+0x1cf/0x21a lib/ubsan.c:190
>   __ubsan_handle_mul_overflow+0x2a/0x35 lib/ubsan.c:214
>   bcm_timeval_to_ktime include/linux/ktime.h:42 [inline]
>   bcm_rx_setup net/can/bcm.c:1189 [inline]
>   bcm_sendmsg+0x35ea/0x3fd0 net/can/bcm.c:1355
>   sock_sendmsg_nosec net/socket.c:621 [inline]
>   sock_sendmsg+0xdd/0x130 net/socket.c:631
>   sock_write_iter+0x24b/0x3d0 net/socket.c:900
>   call_write_iter include/linux/fs.h:1811 [inline]
>   new_sync_write fs/read_write.c:474 [inline]
>   __vfs_write+0x538/0x6e0 fs/read_write.c:487
>   vfs_write+0x1b3/0x520 fs/read_write.c:549
>   ksys_write+0xde/0x1c0 fs/read_write.c:598
>   __do_sys_write fs/read_write.c:610 [inline]
>   __se_sys_write fs/read_write.c:607 [inline]
>   __x64_sys_write+0x7e/0xc0 fs/read_write.c:607
>   do_syscall_64+0xc4/0x510 arch/x86/entry/common.c:290
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x4497b9
> Code: e8 8c 9f 02 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 9b 6b fc ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007f6045f43c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> RAX: ffffffffffffffda RBX: 00007f6045f446cc RCX: 00000000004497b9
> RDX: 0000000000000048 RSI: 00000000200000c0 RDI: 0000000000000013
> RBP: 000000000071bea0 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
> R13: 000000000000ba60 R14: 00000000006f4b00 R15: 00007f6045f44700
> =========================================
> 
> Thanks,
> Kyungtae Kim
>