linux-kernel - [PATCH 3.16 05/61] slip: Fix use-after-free Read in slip

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Message-ID: <lsq.1591725832.69289718@decadent.org.uk>
Date:   Tue, 09 Jun 2020 19:03:56 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Jouni Hogander" <jouni.hogander@...kie.com>,
        "Lukas Bulwahn" <lukas.bulwahn@...il.com>,
        "David Miller" <davem@...emloft.net>,
        "Oliver Hartkopp" <socketcan@...tkopp.net>,
        syzbot+4d5170758f3762109542@...kaller.appspotmail.com
Subject: [PATCH 3.16 05/61] slip: Fix use-after-free Read in slip_open

3.16.85-rc1 review patch.  If anyone has any objections, please let me know.

------------------

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

commit e58c1912418980f57ba2060017583067f5f71e52 upstream.

Slip_open doesn't clean-up device which registration failed from the
slip_devs device list. On next open after failure this list is iterated
and freed device is accessed. Fix this by calling sl_free_netdev in error
path.

Here is the trace from the Syzbot:

__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x197/0x210 lib/dump_stack.c:118
print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374
__kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506
kasan_report+0x12/0x20 mm/kasan/common.c:634
__asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:132
sl_sync drivers/net/slip/slip.c:725 [inline]
slip_open+0xecd/0x11b7 drivers/net/slip/slip.c:801
tty_ldisc_open.isra.0+0xa3/0x110 drivers/tty/tty_ldisc.c:469
tty_set_ldisc+0x30e/0x6b0 drivers/tty/tty_ldisc.c:596
tiocsetd drivers/tty/tty_io.c:2334 [inline]
tty_ioctl+0xe8d/0x14f0 drivers/tty/tty_io.c:2594
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:509 [inline]
do_vfs_ioctl+0xdb6/0x13e0 fs/ioctl.c:696
ksys_ioctl+0xab/0xd0 fs/ioctl.c:713
__do_sys_ioctl fs/ioctl.c:720 [inline]
__se_sys_ioctl fs/ioctl.c:718 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
do_syscall_64+0xfa/0x760 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Fixes: 3b5a39979daf ("slip: Fix memory leak in slip_open error path")
Reported-by: syzbot+4d5170758f3762109542@...kaller.appspotmail.com
Cc: David 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>
Signed-off-by: David S. Miller <davem@...emloft.net>
[bwh: Backported to 3.16: sl_free_netdev() calls free_netdev() here, so
 delete the direct call to free_netdev()]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
--- a/drivers/net/slip/slip.c
+++ b/drivers/net/slip/slip.c
@@ -867,7 +867,7 @@ err_free_chan:
 	sl->tty = NULL;
 	tty->disc_data = NULL;
 	clear_bit(SLF_INUSE, &sl->flags);
-	free_netdev(sl->dev);
+	sl_free_netdev(sl->dev);
 
 err_exit:
 	rtnl_unlock();