linux-kernel - Re: [PATCH][next] cpumask: allocate enough space for string and trailing '\0' char

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Date:   Mon, 09 Nov 2020 20:07:10 -0500
From:   Qian Cai <cai@...hat.com>
To:     Colin King <colin.king@...onical.com>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org,
        Linux Next Mailing List <linux-next@...r.kernel.org>
Subject: Re: [PATCH][next] cpumask: allocate enough space for string and
 trailing '\0' char

On Mon, 2020-11-09 at 13:04 +0000, Colin King wrote:
> From: Colin Ian King <colin.king@...onical.com>
> 
> Currently the allocation of cpulist is based on the length of buf but does
> not include the addition end of string '\0' terminator. Static analysis is
> reporting this as a potential out-of-bounds access on cpulist. Fix this by
> allocating enough space for the additional '\0' terminator.
> 
> Addresses-Coverity: ("Out-of-bounds access")
> Fixes: 65987e67f7ff ("cpumask: add "last" alias for cpu list specifications")

Yeah, this bad commit also introduced KASAN errors everywhere and then will
disable lockdep that makes our linux-next CI miserable. Confirmed that this
patch will fix it.

> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>  lib/cpumask.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/lib/cpumask.c b/lib/cpumask.c
> index 34ecb3005941..cb8a3ef0e73e 100644
> --- a/lib/cpumask.c
> +++ b/lib/cpumask.c
> @@ -185,7 +185,7 @@ int __ref cpulist_parse(const char *buf, struct cpumask
> *dstp)
>  {
>  	int r;
>  	char *cpulist, last_cpu[5];	/* NR_CPUS <= 9999 */
> -	size_t len = strlen(buf);
> +	size_t len = strlen(buf) + 1;
>  	bool early = !slab_is_available();
>  
>  	if (!strcmp(buf, "all")) {