Re: [PATCH v2 4/6] doc/migration: Use snprintf() for socket path and fix argv access

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

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On Thu, Jul 09, 2026 at 05:56:54PM -0400, Jon Maloy wrote:
> Replace strcpy() with snprintf() when copying the helper socket path
> into sun_path, preventing a potential buffer overflow from a long
> argument and guaranteeing null-termination.
> 
> In target.c, move the argc check before accessing argv[4], so we
> don't dereference past the end of argv.
> 
> Signed-off-by: Jon Maloy <jmaloy@redhat.com>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

Although... it wouldn't surprise me if some static checker now
complains about not testing the return value from snprintf().

> 
> ---
> v2: Use snprintf() instead of strncpy() for clarity and
>     guaranteed null-termination, as suggested by David Gibson
> ---
>  doc/migration/source.c | 2 +-
>  doc/migration/target.c | 8 +++-----
>  2 files changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/doc/migration/source.c b/doc/migration/source.c
> index d44ebf1f..8aad0259 100644
> --- a/doc/migration/source.c
> +++ b/doc/migration/source.c
> @@ -47,7 +47,7 @@ int main(int argc, char **argv)
>  		return -1;
>  	}
>  
> -	strcpy(a_helper.sun_path, argv[4]);
> +	snprintf(a_helper.sun_path, sizeof(a_helper.sun_path), "%s", argv[4]);
>  	getaddrinfo(argv[1], argv[2], &hints, &r);
>  
>  	/* Connect socket to server and send some data */
> diff --git a/doc/migration/target.c b/doc/migration/target.c
> index f7d31083..e2469837 100644
> --- a/doc/migration/target.c
> +++ b/doc/migration/target.c
> @@ -38,11 +38,6 @@ int main(int argc, char **argv)
>  	struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
>  	struct addrinfo *r;
>  
> -	(void)argc;
> -
> -	strcpy(a_helper.sun_path, argv[4]);
> -	getaddrinfo(argv[1], argv[2], &hints, &r);
> -
>  	if (argc != 7) {
>  		fprintf(stderr,
>  			"%s DST_ADDR DST_PORT SRC_PORT HELPER_PATH SSEQ RSEQ\n",
> @@ -50,6 +45,9 @@ int main(int argc, char **argv)
>  		return -1;
>  	}
>  
> +	snprintf(a_helper.sun_path, sizeof(a_helper.sun_path), "%s", argv[4]);
> +	getaddrinfo(argv[1], argv[2], &hints, &r);
> +
>  	/* Prepare socket, bind to source port */
>  	s = socket(r->ai_family, SOCK_STREAM, IPPROTO_TCP);
>  	setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &((int){ 1 }), sizeof(int));
> -- 
> 2.52.0
> 

-- 
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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