Subject: Re: [PATCH] slip: Fix memory leak in slip_open error path

From: [email-masked] (Jouni Högander)
Date: Thu, 14 Nov 2019 10:51:18 +0200

[email-masked] (Jouni Högander) writes:

> [email-masked] writes:
>
>> From: Jouni Hogander <[email-masked]>
>>
>> Driver/net/can/slcan.c is derived from slip.c. Memory leak was detected
>> by Syzkaller in slcan. Same issue exists in slip.c and this patch is
>> addressing the leak in slip.c.
>>
>> Here is the slcan memory leak trace reported by Syzkaller:
>>
>> BUG: memory leak unreferenced object 0xffff888067f65500 (size 4096):
>>   comm "syz-executor043", pid 454, jiffies 4294759719 (age 11.930s)
>>   hex dump (first 32 bytes):
>>     73 6c 63 61 6e 30 00 00 00 00 00 00 00 00 00 00 slcan0..........
>>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
>>   backtrace:
>>     [<00000000a06eec0d>] __kmalloc+0x18b/0x2c0
>>     [<0000000083306e66>] kvmalloc_node+0x3a/0xc0
>>     [<000000006ac27f87>] alloc_netdev_mqs+0x17a/0x1080
>>     [<0000000061a996c9>] slcan_open+0x3ae/0x9a0
>>     [<000000001226f0f9>] tty_ldisc_open.isra.1+0x76/0xc0
>>     [<0000000019289631>] tty_set_ldisc+0x28c/0x5f0
>>     [<000000004de5a617>] tty_ioctl+0x48d/0x1590
>>     [<00000000daef496f>] do_vfs_ioctl+0x1c7/0x1510
>>     [<0000000059068dbc>] ksys_ioctl+0x99/0xb0
>>     [<000000009a6eb334>] __x64_sys_ioctl+0x78/0xb0
>>     [<0000000053d0332e>] do_syscall_64+0x16f/0x580
>>     [<0000000021b83b99>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
>>     [<000000008ea75434>] 0xfffffffffffffff
>>
>> Cc: "David S. Miller" <[email-masked]>
>> Cc: Oliver Hartkopp <[email-masked]>
>> Cc: Lukas Bulwahn <[email-masked]>
>> Signed-off-by: Jouni Hogander <[email-masked]>
>> ---
>>  drivers/net/slip/slip.c | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/net/slip/slip.c b/drivers/net/slip/slip.c
>> index cac64b96d545..4d479e3c817d 100644
>> --- a/drivers/net/slip/slip.c
>> +++ b/drivers/net/slip/slip.c
>> @@ -855,6 +855,7 @@ static int slip_open(struct tty_struct *tty)
>>  	sl->tty = NULL;
>>  	tty->disc_data = NULL;
>>  	clear_bit(SLF_INUSE, &sl->flags);
>> +	free_netdev(sl->dev);
>>  
>>  err_exit:
>>  	rtnl_unlock();
>
> Observed panic in another error path in my overnight Syzkaller run with
> this patch. Better not to apply it. Sorry for inconvenience.

The panic was caused by another error path fix I had in my Syzkaller
setup. I.e. this patch is ok.

BR,

Jouni Högander