[PATCH v2 net] nfc: nci: assert requested protocol is valid

[Jeremy Cline]

The protocol is used in a bit mask to determine if the protocol is
supported. Assert the provided protocol is less than the maximum
defined so it doesn't potentially perform a shift-out-of-bounds and
provide a clearer error for undefined protocols vs unsupported ones.

Fixes: 6a2968aaf50c ("NFC: basic NCI protocol implementation")
Reported-and-tested-by: syzbot+0839b78e119aae1fec78@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=0839b78e119aae1fec78
Signed-off-by: Jeremy Cline <jeremy@xxxxxxxxxx>
---
Changes from v1:
    - Target the correct tree (net)

 net/nfc/nci/core.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/nfc/nci/core.c b/net/nfc/nci/core.c
index fff755dde30d..6c9592d05120 100644
--- a/net/nfc/nci/core.c
+++ b/net/nfc/nci/core.c
@@ -909,6 +909,11 @@ static int nci_activate_target(struct nfc_dev *nfc_dev,
 		return -EINVAL;
 	}
 
+	if (protocol >= NFC_PROTO_MAX) {
+		pr_err("the requested nfc protocol is invalid\n");
+		return -EINVAL;
+	}
+
 	if (!(nci_target->supported_protocols & (1 << protocol))) {
 		pr_err("target does not support the requested protocol 0x%x\n",
 		       protocol);
-- 
2.41.0