[PATCH] BSS: Fix use-after-realloc

Jouni Malinen j
Mon Mar 5 06:22:27 PST 2012

On Mon, Mar 05, 2012 at 12:30:15PM +0200, Eliad Peller wrote:
> After reallocation of the bss struct, current_bss
> wasn't updated and could hold an invalid pointer
> (which might get dereferenced later).
> Update current_bss if the pointer was changed.

Thanks for catching this!

> realloc is pretty dangerous if a reference could be
> saved somewhere. i suspect there might be similar issues
> in the codebase, but i haven't looked at it throughtly.

realloc is not the only reason for that.. Similar cases apply for
configuration re-read, but I would hope that those are all covered with
clearing current_ssid.

> diff --git a/wpa_supplicant/bss.c b/wpa_supplicant/bss.c
> @@ -333,6 +333,8 @@ static void wpa_bss_update(struct wpa_supplicant *wpa_s, struct wpa_bss *bss,
>  				  res->ie_len + res->beacon_ie_len);
>  			bss->ie_len = res->ie_len;
>  			bss->beacon_ie_len = res->beacon_ie_len;
> +			if (wpa_s->current_bss == bss)
> +				wpa_s->current_bss = nbss;

This is broken.. bss == nbss here. I would assume you wanted to do that
just before the "bss = nbss;" line.

Jouni Malinen                                            PGP id EFC895FA

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