Re: [PATCH 5.3 09/48] slip: Fix memory leak in slip_open error path

[Oliver Hartkopp]

Hello Greg,

thanks for taking care of the slip.c patches.

The original issue was reported by Jouni for "slcan.c" which is also 
referenced in this commit message. But it was probably overlooked at 
upstream time that it should go into stable too.

The slcan.c fix is here:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ed50e1600b4483c049ce76e6bd3b665a6a9300ed

Best regards,
Oliver

On 19/11/2019 06.19, Greg Kroah-Hartman wrote:
> From: Jouni Hogander <jouni.hogander@xxxxxxxxxx>
>
> [ Upstream commit 3b5a39979dafea9d0cd69c7ae06088f7a84cdafa ]
>
> 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" <davem@xxxxxxxxxxxxx>
> Cc: Oliver Hartkopp <socketcan@xxxxxxxxxxxx>
> Cc: Lukas Bulwahn <lukas.bulwahn@xxxxxxxxx>
> Signed-off-by: Jouni Hogander <jouni.hogander@xxxxxxxxxx>
> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> ---
>   drivers/net/slip/slip.c |    1 +
>   1 file changed, 1 insertion(+)
>
> --- a/drivers/net/slip/slip.c
> +++ b/drivers/net/slip/slip.c
> @@ -855,6 +855,7 @@ err_free_chan:
>   	sl->tty = NULL;
>   	tty->disc_data = NULL;
>   	clear_bit(SLF_INUSE, &sl->flags);
> +	free_netdev(sl->dev);
>   
>   err_exit:
>   	rtnl_unlock();