netdev - [PATCH] slip: Fix memory leak in slip

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Date:   Wed, 13 Nov 2019 13:45:02 +0200
From:   jouni.hogander@...kie.com
To:     netdev@...r.kernel.org
Cc:     Jouni Hogander <jouni.hogander@...kie.com>,
        "David S. Miller" <davem@...emloft.net>,
        Oliver Hartkopp <socketcan@...tkopp.net>,
        Lukas Bulwahn <lukas.bulwahn@...il.com>
Subject: [PATCH] slip: Fix memory leak in slip_open error path

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

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@...emloft.net>
Cc: Oliver Hartkopp <socketcan@...tkopp.net>
Cc: Lukas Bulwahn <lukas.bulwahn@...il.com>
Signed-off-by: Jouni Hogander <jouni.hogander@...kie.com>
---
 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();
-- 
2.17.1