Re: [PATCH 1/4] conf: Copy up to MAXDNSRCH - 1 bytes, not MAXDNSRCH

[David Gibson <david@gibson.dropbear.id.au>]

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On Thu, Jun 27, 2024 at 01:45:33AM +0200, Stefano Brivio wrote:
> Spotted by Coverity just recently. Not that it really matters as
> MAXDNSRCH always appears to be defined as 1025, while a full domain
> name can have up to 253 characters: it would be a bit pointless to
> have a longer search domain.
> 
> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

Hm.  So, IIRC strncpy() won't \0 terminate in the case where it
truncates.  I guess we'll get away with that here since we expect
c->dns_search to be filled with \0 before hand.  That's... more
fragile than ideal, though.

> ---
>  conf.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/conf.c b/conf.c
> index e1f5422..9e47e9a 100644
> --- a/conf.c
> +++ b/conf.c
> @@ -453,7 +453,7 @@ static void get_dns(struct ctx *c)
>  			while (s - c->dns_search < ARRAY_SIZE(c->dns_search) - 1
>  			       /* cppcheck-suppress strtokCalled */
>  			       && (p = strtok(NULL, " \t"))) {
> -				strncpy(s->n, p, sizeof(c->dns_search[0]));
> +				strncpy(s->n, p, sizeof(c->dns_search[0]) - 1);
>  				s++;
>  				*s->n = 0;
>  			}

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

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