On 03/12/2019 11.47, Marc Kleine-Budde wrote:

From: Jouni Hogander jouni.hogander@unikie.com

Slcan_open doesn't clean-up device which registration failed from the slcan_devs device list. On next open this list is iterated and freed device is accessed. Fix this by calling slc_free_netdev in error path.

Driver/net/can/slcan.c is derived from slip.c. Use-after-free error was identified in slip_open by syzboz. Same bug is in slcan.c. Here is the trace from the Syzbot slip report:

__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: ed50e1600b44 ("slcan: Fix memory leak in error path") Cc: Wolfgang Grandegger wg@grandegger.com Cc: Marc Kleine-Budde mkl@pengutronix.de Cc: David 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 Cc: linux-stable stable@vger.kernel.org # >= v5.4

I think this problem existed from the initial commit in 2010 and is not restricted to >= v5.4

Together with commit commit ed50e1600b4483c049 ("slcan: Fix memory leak in error path") from Jouni Hogander.

Regards, Oliver

Acked-by: Oliver Hartkopp socketcan@hartkopp.net Signed-off-by: Marc Kleine-Budde mkl@pengutronix.de

---

drivers/net/can/slcan.c | 1 + 1 file changed, 1 insertion(+)

diff --git a/drivers/net/can/slcan.c b/drivers/net/can/slcan.c index 0a9f42e5fedf..2e57122f02fb 100644 --- a/drivers/net/can/slcan.c +++ b/drivers/net/can/slcan.c @@ -617,6 +617,7 @@ static int slcan_open(struct tty_struct *tty) sl->tty = NULL; tty->disc_data = NULL; clear_bit(SLF_INUSE, &sl->flags);

• slc_free_netdev(sl->dev); free_netdev(sl->dev);

err_exit: