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

From: [email-masked] (Jouni Högander)
Date: Thu, 14 Nov 2019 09:25:23 +0200

[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.

BR,

Jouni Högander