nfc: fix segfault in nfc_genl_dump_devices_done

BugLink: https://bugs.launchpad.net/bugs/1956301
commit fd79a0cbf0b2e34bcc45b13acf962e2032a82203 upstream.

When kmalloc in nfc_genl_dump_devices() fails then
nfc_genl_dump_devices_done() segfaults as below

KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
CPU: 0 PID: 25 Comm: kworker/0:1 Not tainted 5.16.0-rc4-01180-g2a987e65025e-dirty #5
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-6.fc35 04/01/2014
Workqueue: events netlink_sock_destruct_work
RIP: 0010:klist_iter_exit+0x26/0x80
Call Trace:
<TASK>
class_dev_iter_exit+0x15/0x20
nfc_genl_dump_devices_done+0x3b/0x50
genl_lock_done+0x84/0xd0
netlink_sock_destruct+0x8f/0x270
__sk_destruct+0x64/0x3b0
sk_destruct+0xa8/0xd0
__sk_free+0x2e8/0x3d0
sk_free+0x51/0x90
netlink_sock_destruct_work+0x1c/0x20
process_one_work+0x411/0x710
worker_thread+0x6fd/0xa80

Link: https://syzkaller.appspot.com/bug?id=fc0fa5a53db9edd261d56e74325419faf18bd0df
Reported-by: syzbot+f9f76f4a0766420b4a02@syzkaller.appspotmail.com
Signed-off-by: Tadeusz Struk <tadeusz.struk@linaro.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20211208182742.340542-1-tadeusz.struk@linaro.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>

diff --git a/net/nfc/netlink.c b/net/nfc/netlink.c
index 082085c25a8e406da5ded5428cb86598740c028a..8048a3dcc5f8ba80cc18f61b838e848ae62cd9c5 100644 (file)
--- a/net/nfc/netlink.c
+++ b/net/nfc/netlink.c
@@ -636,8 +636,10 @@ static int nfc_genl_dump_devices_done(struct netlink_callback *cb)
 {
        struct class_dev_iter *iter = (struct class_dev_iter *) cb->args[0];
 
-       nfc_device_iter_exit(iter);
-       kfree(iter);
+       if (iter) {
+               nfc_device_iter_exit(iter);
+               kfree(iter);
+       }
 
        return 0;
 }