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

ZheyuMa · gregkh · commit 689ca31c5426 · 2022-04-14T18:26:30.000+02:00
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. Reviewed-by: Jiri Slaby <jirislaby@kernel.org> Signed-off-by: Zheyu Ma <zheyuma97@gmail.com> Link: https://lore.kernel.org/r/20220410114814.3920474-1-zheyuma97@gmail.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git 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;

Original file line number	Diff line number	Diff line change
`@@ -1746,6 +1746,8 @@ static int hdlcdev_init(struct slgt_info *info)`
`1746`	`1746`	`*/`
`1747`	`1747`	`static void hdlcdev_exit(struct slgt_info *info)`
`1748`	`1748`	`{`
	`1749`	`+ if (!info->netdev)`
	`1750`	`+ return;`
`1749`	`1751`	`unregister_hdlc_device(info->netdev);`
`1750`	`1752`	`free_netdev(info->netdev);`
`1751`	`1753`	`info->netdev = NULL;`