linux-kernel - Re: [PATCH] apparmor: fix off-by-one comparison on MAXMAPPED

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Message-ID: <1a49cc0a-949b-7821-6a32-d0e71a3491ec@canonical.com>
Date:   Mon, 25 Sep 2017 10:21:35 -0400
From:   John Johansen <john.johansen@...onical.com>
To:     Colin King <colin.king@...onical.com>,
        James Morris <james.l.morris@...cle.com>,
        "Serge E . Hallyn" <serge@...lyn.com>,
        linux-security-module@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] apparmor: fix off-by-one comparison on MAXMAPPED_SIG

On 08/22/2017 05:58 PM, Colin King wrote:
> From: Colin Ian King <colin.king@...onical.com>
> 
> There is a an off-by-one comparision on sig against MAXMAPPED_SIG
> that can lead to a read outside the sig_map array if sig
> is MAXMAPPED_SIG. Fix this.
> 
> Detected with cppcheck:
> "Either the condition 'sig<=35' is redundant or the array 'sig_map[35]'
> is accessed at index 35, which is out of bounds."
> 
> Fixes: c6bf1adaecaa ("apparmor: add the ability to mediate signals")
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>  security/apparmor/ipc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/security/apparmor/ipc.c b/security/apparmor/ipc.c
> index 66fb9ede9447..5091c78062e4 100644
> --- a/security/apparmor/ipc.c
> +++ b/security/apparmor/ipc.c
> @@ -128,7 +128,7 @@ static inline int map_signal_num(int sig)
>  		return SIGUNKNOWN;
>  	else if (sig >= SIGRTMIN)
>  		return sig - SIGRTMIN + 128;	/* rt sigs mapped to 128 */
> -	else if (sig <= MAXMAPPED_SIG)
> +	else if (sig < MAXMAPPED_SIG)
>  		return sig_map[sig];
>  	return SIGUNKNOWN;
>  }
> 

I've pulled this in to apparmor-next