[PATCH] tty: synclink_gt: Fix null-pointer-dereference in slgt_clean()

From: Zheyu Ma
Date: Sun Apr 10 2022 - 07:55:38 EST


When the driver fails at alloc_hdlcdev(), and then we remove the driver
module, we will get the following splat:

[ 25.065966] general protection fault, probably for non-canonical address 0xdffffc0000000182: 0000 [#1] PREEMPT SMP KASAN PTI
[ 25.066914] KASAN: null-ptr-deref in range [0x0000000000000c10-0x0000000000000c17]
[ 25.069262] RIP: 0010:detach_hdlc_protocol+0x2a/0x3e0
[ 25.077709] Call Trace:
[ 25.077924] <TASK>
[ 25.078108] unregister_hdlc_device+0x16/0x30
[ 25.078481] slgt_cleanup+0x157/0x9f0 [synclink_gt]

Fix this by checking whether the 'info->netdev' is a null pointer first.

Signed-off-by: Zheyu Ma <zheyuma97@xxxxxxxxx>
---
drivers/tty/synclink_gt.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/tty/synclink_gt.c b/drivers/tty/synclink_gt.c
index 25c558e65ece..9bc2a9265277 100644
--- a/drivers/tty/synclink_gt.c
+++ b/drivers/tty/synclink_gt.c
@@ -1746,6 +1746,8 @@ static int hdlcdev_init(struct slgt_info *info)
*/
static void hdlcdev_exit(struct slgt_info *info)
{
+ if (!info->netdev)
+ return;
unregister_hdlc_device(info->netdev);
free_netdev(info->netdev);
info->netdev = NULL;
--
2.25.1