[DTrace-devel] [PATCH 05/14] probe: get the size of the hash-lookup key right

[Kris Van Hees]

On Thu, Oct 24, 2024 at 12:37:49PM +0100, Nick Alcock wrote:
> This was allocated with alloca() but then snprintf()ed with a size of
> INT_MAX.  This makes _FORTIFY_SOURCE rightly unhappy.
> 
> Passing in the size we actually allocated is trivial.

Except for the fact that dt_probe_keylen() and dt_probe_key() are only
ever used from dt_probe_lookup2().  So, getting rid of those two functions
and rewriting the call as shown below seems to be a much better fix.

> Signed-off-by: Nick Alcock <nick.alcock at oracle.com>
> Bug: https://github.com/oracle/dtrace-utils/issues/78
> ---
>  libdtrace/dt_probe.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/libdtrace/dt_probe.c b/libdtrace/dt_probe.c
> index 686e2a661253..bb1773ee60d4 100644
> --- a/libdtrace/dt_probe.c
> +++ b/libdtrace/dt_probe.c
> @@ -180,9 +180,9 @@ dt_probe_keylen(const dtrace_probedesc_t *pdp)
>  }
>  
>  static char *
> -dt_probe_key(const dtrace_probedesc_t *pdp, char *s)
> +dt_probe_key(const dtrace_probedesc_t *pdp, char *s, size_t len)
>  {
> -	snprintf(s, INT_MAX, "%s:%s:%s", pdp->mod, pdp->fun, pdp->prb);
> +	snprintf(s, len, "%s:%s:%s", pdp->mod, pdp->fun, pdp->prb);
>  	return s;
>  }
>  
> @@ -204,7 +204,7 @@ dt_probe_lookup2(dt_provider_t *pvp, const char *s)
>  		return NULL; /* dt_errno is set for us */
>  
>  	keylen = dt_probe_keylen(&pd);
> -	key = dt_probe_key(&pd, alloca(keylen));
> +	key = dt_probe_key(&pd, alloca(keylen), keylen);

Better would be:
	if (asprintf(&key, "%s:%s:%s", pdp->mod, pdp->fun, pdp->prb) == -1) {
		dt_set_errno(dtp, errno);
		return NULL;
	}

>  
>  	/*
>  	 * If the probe is already declared, then return the dt_probe_t from
> -- 
> 2.46.0.278.g36e3a12567
>