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@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=0839b78e119aae1fec78
Signed-off-by: Jeremy Cline <jeremy@jcline.org>
---
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

Hello:

This patch was applied to netdev/net.git (main)
by Paolo Abeni <pabeni@redhat.com>:

On Mon,  9 Oct 2023 16:00:54 -0400 you wrote:
> 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@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=0839b78e119aae1fec78
> Signed-off-by: Jeremy Cline <jeremy@jcline.org>
> 
> [...]

Here is the summary with links:
  - [v2,net] nfc: nci: assert requested protocol is valid
    https://git.kernel.org/netdev/net/c/354a6e707e29

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

On Mon, Oct 09, 2023 at 04:00:54PM -0400, Jeremy Cline wrote:
> 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@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=0839b78e119aae1fec78
> Signed-off-by: Jeremy Cline <jeremy@jcline.org>

As per my review of v1, this looks good to me.

Reviewed-by: Simon Horman <horms@kernel.org>