[PATCH AUTOSEL 4.9 08/13] slip: Fix memory leak in slip_open error path

[Sasha Levin <sashal@kernel.org>]

From: Jouni Hogander <jouni.hogander@unikie.com>

[ 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@davemloft.net>
Cc: Oliver Hartkopp <socketcan@hartkopp.net>
Cc: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Jouni Hogander <jouni.hogander@unikie.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 9ed6d1c1ee45f..b2317b3a542a0 100644
--- a/drivers/net/slip/slip.c
+++ b/drivers/net/slip/slip.c
@@ -860,6 +860,7 @@ 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();
-- 
2.20.1