At the moment of the check, `cmd->num_cis` holds the value of 0x1f,
which is the max number of elements in the `cmd->cis[]` array at
declaration, which is 0x1f.

So, avoid using 0x1f directly, and instead use `cmd->num_cis`. Similarly
to this other patch[1].

Link: https://lore.kernel.org/linux-hardening/ZivaHUQyDDK9fXEk@neat/ [1]
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
 net/bluetooth/hci_sync.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
index 6e15594d3565..af9513f3c451 100644
--- a/net/bluetooth/hci_sync.c
+++ b/net/bluetooth/hci_sync.c
@@ -6559,7 +6559,7 @@ int hci_le_create_cis_sync(struct hci_dev *hdev)
 		cis->cis_handle = cpu_to_le16(conn->handle);
 		aux_num_cis++;
 
-		if (aux_num_cis >= 0x1f)
+		if (aux_num_cis >= cmd->num_cis)
 			break;
 	}
 	cmd->num_cis = aux_num_cis;
-- 
2.34.1

On Wed, May 01, 2024 at 11:50:02AM -0600, Gustavo A. R. Silva wrote:
> At the moment of the check, `cmd->num_cis` holds the value of 0x1f,
> which is the max number of elements in the `cmd->cis[]` array at
> declaration, which is 0x1f.
> 
> So, avoid using 0x1f directly, and instead use `cmd->num_cis`. Similarly
> to this other patch[1].
> 
> Link: https://lore.kernel.org/linux-hardening/ZivaHUQyDDK9fXEk@neat/ [1]
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> ---
>  net/bluetooth/hci_sync.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
> index 6e15594d3565..af9513f3c451 100644
> --- a/net/bluetooth/hci_sync.c
> +++ b/net/bluetooth/hci_sync.c
> @@ -6559,7 +6559,7 @@ int hci_le_create_cis_sync(struct hci_dev *hdev)
>  		cis->cis_handle = cpu_to_le16(conn->handle);
>  		aux_num_cis++;
>  
> -		if (aux_num_cis >= 0x1f)
> +		if (aux_num_cis >= cmd->num_cis)
>  			break;
>  	}
>  	cmd->num_cis = aux_num_cis;

Yeah, good idea. No need to repeat a hard-coded value.

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook