[PATCH] nfc: fix segfault in nfc_genl_dump_devices_done

* [PATCH] nfc: fix segfault in nfc_genl_dump_devices_done
@ 2021-12-08 18:27 Tadeusz Struk
  2021-12-09  8:12 ` Krzysztof Kozlowski
  2021-12-09 16:00 ` patchwork-bot+netdevbpf
  0 siblings, 2 replies; 3+ messages in thread
From: Tadeusz Struk @ 2021-12-08 18:27 UTC (permalink / raw)
  To: netdev
  Cc: Tadeusz Struk, Krzysztof Kozlowski, David S. Miller,
	Jakub Kicinski, stable, syzbot+f9f76f4a0766420b4a02

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
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: netdev@vger.kernel.org
Cc: stable@vger.kernel.org
Reported-by: syzbot+f9f76f4a0766420b4a02@syzkaller.appspotmail.com
Signed-off-by: Tadeusz Struk <tadeusz.struk@linaro.org>
---
 net/nfc/netlink.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/nfc/netlink.c b/net/nfc/netlink.c
index 334f63c9529e..0b4fae183a4b 100644
--- 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;
 }
-- 
2.33.1


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