Messages in this thread | | | Subject | Re: UBSAN: Undefined behaviour in net/can/bcm.c | From | Oliver Hartkopp <> | Date | Sat, 12 Jan 2019 21:02:43 +0100 |
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Hi,
thanks for the report!
On 1/12/19 8:25 PM, Kyungtae Kim wrote: > We report a bug in linux-4.19.13: "UBSAN: Undefined behaviour in net/can/bcm.c" > > kernel config: https://kt0755.github.io/etc/config_4.19.13 > repro: https://kt0755.github.io/etc/repro.296b5.c > > An integer overflow arose in bcm_timeval_to_ktime() when > tv.tv_usec * NSEC_PER_USEC is larger than its boundary of the > destination (i.e., long). > To fix, an appropriate boundary check should be placed right before the usage.
Just checked the commit that introduced the issue:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ba61a8d9d7809
In fact the tv.tv_usec needs to be checked to be smaller than 1000*1000 before multiplying with 1000 (NSEC_PER_USEC).
The code in question
static inline ktime_t bcm_timeval_to_ktime(struct bcm_timeval tv) { return ktime_set(tv.tv_sec, tv.tv_usec * NSEC_PER_USEC); }
is a 1:1 copy of the standard function in ktime.h
/* convert a timeval to ktime_t format: */ static inline ktime_t timeval_to_ktime(struct timeval tv) { return ktime_set(tv.tv_sec, tv.tv_usec * NSEC_PER_USEC); }
https://elixir.bootlin.com/linux/v4.20.1/source/include/linux/ktime.h#L81
And therefore I thought it was a good choice ;-)
So there could potentially be some other users of timeval_to_ktime() that might have the same issue.
Will provide a check in bcm.c in rx_setup and tx_setup as the timeval content can be provided from user space there.
@Arnd: Do you have a better idea?
Thanks & best regards, Oliver
> ========================================= > UBSAN: Undefined behaviour in net/can/bcm.c:140:41 > signed integer overflow: > 60870466536963773 * 1000 cannot be represented in type 'long int' > CPU: 0 PID: 7063 Comm: syz-executor3 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 net/can/bcm.c:140 [inline] > bcm_rx_setup net/can/bcm.c:1190 [inline] > bcm_sendmsg+0x3807/0x3fd0 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:00007fc2e6feac68 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 > RAX: ffffffffffffffda RBX: 00007fc2e6feb6cc 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: 00007fc2e6feb700 > ========================================= > > Thanks, > Kyungtae Kim >
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