[PATCH v2 net] net: nfc: llcp: Add lock when modifying device list

[Jeremy Cline]

The device list needs its associated lock held when modifying it, or the
list could become corrupted, as syzbot discovered.

Reported-and-tested-by: syzbot+c1d0a03d305972dbbe14@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=c1d0a03d305972dbbe14
Fixes: 6709d4b7bc2e ("net: nfc: Fix use-after-free caused by nfc_llcp_find_local")
Signed-off-by: Jeremy Cline <jeremy@xxxxxxxxxx>
---
Changes from v1: added the correct Fixes tag

 net/nfc/llcp_core.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/nfc/llcp_core.c b/net/nfc/llcp_core.c
index f60e424e0607..6705bb895e23 100644
--- a/net/nfc/llcp_core.c
+++ b/net/nfc/llcp_core.c
@@ -1636,7 +1636,9 @@ int nfc_llcp_register_device(struct nfc_dev *ndev)
 	timer_setup(&local->sdreq_timer, nfc_llcp_sdreq_timer, 0);
 	INIT_WORK(&local->sdreq_timeout_work, nfc_llcp_sdreq_timeout_work);
 
+	spin_lock(&llcp_devices_lock);
 	list_add(&local->list, &llcp_devices);
+	spin_unlock(&llcp_devices_lock);
 
 	return 0;
 }
-- 
2.41.0