linux-kernel - Re: [PATCH] nfx: llcp: fix possible use of uninitialized variable in nfc_llcp_send

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Message-ID: <ZGCdYF7rfDO7V7mH@corigine.com>
Date:   Sun, 14 May 2023 10:35:44 +0200
From:   Simon Horman <simon.horman@...igine.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Samuel Ortiz <sameo@...ux.intel.com>,
        Thierry Escande <thierry.escande@...labora.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] nfx: llcp: fix possible use of uninitialized variable in
 nfc_llcp_send_connect()

On Sat, May 13, 2023 at 01:49:38PM +0200, Krzysztof Kozlowski wrote:
> If sock->service_name is NULL, the local variable
> service_name_tlv_length will not be assigned by nfc_llcp_build_tlv(),
> later leading to using value frmo the stack.  Smatch warning:
> 
>   net/nfc/llcp_commands.c:442 nfc_llcp_send_connect() error: uninitialized symbol 'service_name_tlv_length'.
> 
> Fixes: de9e5aeb4f40 ("NFC: llcp: Fix usage of llcp_add_tlv()")
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> ---
>  net/nfc/llcp_commands.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/net/nfc/llcp_commands.c b/net/nfc/llcp_commands.c
> index 41e3a20c8935..cdb001de0692 100644
> --- a/net/nfc/llcp_commands.c
> +++ b/net/nfc/llcp_commands.c
> @@ -390,7 +390,8 @@ int nfc_llcp_send_connect(struct nfc_llcp_sock *sock)
>  	const u8 *service_name_tlv = NULL;
>  	const u8 *miux_tlv = NULL;
>  	const u8 *rw_tlv = NULL;
> -	u8 service_name_tlv_length, miux_tlv_length,  rw_tlv_length, rw;
> +	u8 service_name_tlv_length = 0;
> +	u8 miux_tlv_length,  rw_tlv_length, rw;

While moving this around, can reduce the number of spaces before rw_tlv_length?

>  	int err;
>  	u16 size = 0;
>  	__be16 miux;
> -- 
> 2.34.1
> 
>