netdev - Re: [PATCH iproute2 1/1] bpf: Fix segfault when custom pinning is used

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Message-ID: <20200422064215.GA17201@nautica>
Date:   Wed, 22 Apr 2020 08:42:15 +0200
From:   Dominique Martinet <asmadeus@...ewreck.org>
To:     Jamal Hadi Salim <jhs@...atatu.com>
Cc:     stephen@...workplumber.org, netdev@...r.kernel.org,
        dsahern@...il.com, aclaudi@...hat.com, daniel@...earbox.net,
        Jamal Hadi Salim <hadi@...atatu.com>
Subject: Re: [PATCH iproute2 1/1] bpf: Fix segfault when custom pinning is
 used

(random review)

Jamal Hadi Salim wrote on Tue, Apr 21, 2020:
> diff --git a/lib/bpf.c b/lib/bpf.c
> index 10cf9bf4..cf636c9e 100644
> --- a/lib/bpf.c
> +++ b/lib/bpf.c
> @@ -1509,12 +1509,12 @@ out:
>  static int bpf_make_custom_path(const struct bpf_elf_ctx *ctx,
>  				const char *todo)
>  {
> -	char *tmp = NULL;
> +	char tmp[PATH_MAX] = {};
>  	char *rem = NULL;
>  	char *sub;
>  	int ret;
>  
> -	ret = asprintf(&tmp, "%s/../", bpf_get_work_dir(ctx->type));
> +	ret = sprintf(tmp, "%s/../", bpf_get_work_dir(ctx->type));
>  	if (ret < 0) {
>  		fprintf(stderr, "asprintf failed: %s\n", strerror(errno));

error check needs to be reworded, and it probably needs to use snprintf
instead of sprintf: bpf_get_work_dir() can be up to PATH_MAX long and as
pointed out there are strcat() afterwards so it's still possible to
overflow this one

-- 
Dominique