[PATCH] libertas: fix buffer overrun

[PATCH] libertas: fix buffer overrun

[Johannes Berg]

If somebody sends an invalid beacon/probe response, that can trash the
whole BSS descriptor. The descriptor is, luckily, large enough so that
it cannot scribble past the end of it; it's well above 400 bytes long.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Cc: stable@kernel.org [2.6.24-2.6.27, bug present in some form since driver was added (2.6.22)]
---
Not really tested for lack of hw.

John, this is part of the other patch I sent, but this one's
for 2.6.28.

The function there needs to be reviewed more, it seems to access
potentially invalid memory when an AP sends other, too short,
information elements.

--- a/drivers/net/wireless/libertas/scan.c
+++ b/drivers/net/wireless/libertas/scan.c
@@ -598,8 +598,8 @@ static int lbs_process_bss(struct bss_descriptor *bss,
 
 		switch (elem->id) {
 		case MFIE_TYPE_SSID:
-			bss->ssid_len = elem->len;
-			memcpy(bss->ssid, elem->data, elem->len);
+			bss->ssid_len = min_t(int, 32, elem->len);
+			memcpy(bss->ssid, elem->data, bss->ssid_len);
 			lbs_deb_scan("got SSID IE: '%s', len %u\n",
 			             escape_essid(bss->ssid, bss->ssid_len),
 			             bss->ssid_len);

Re: [PATCH] libertas: fix buffer overrun

[Dan Williams]

On Wed, 2008-10-29 at 11:43 +0100, Johannes Berg wrote:
> If somebody sends an invalid beacon/probe response, that can trash the
> whole BSS descriptor. The descriptor is, luckily, large enough so that
> it cannot scribble past the end of it; it's well above 400 bytes long.
> 
> Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
> Cc: stable@kernel.org [2.6.24-2.6.27, bug present in some form since driver was added (2.6.22)]

Acked-by: Dan Williams <dcbw@redhat.com>

> ---
> Not really tested for lack of hw.
> 
> John, this is part of the other patch I sent, but this one's
> for 2.6.28.
> 
> The function there needs to be reviewed more, it seems to access
> potentially invalid memory when an AP sends other, too short,
> information elements.
> 
> --- a/drivers/net/wireless/libertas/scan.c
> +++ b/drivers/net/wireless/libertas/scan.c
> @@ -598,8 +598,8 @@ static int lbs_process_bss(struct bss_descriptor *bss,
>  
>  		switch (elem->id) {
>  		case MFIE_TYPE_SSID:
> -			bss->ssid_len = elem->len;
> -			memcpy(bss->ssid, elem->data, elem->len);
> +			bss->ssid_len = min_t(int, 32, elem->len);
> +			memcpy(bss->ssid, elem->data, bss->ssid_len);
>  			lbs_deb_scan("got SSID IE: '%s', len %u\n",
>  			             escape_essid(bss->ssid, bss->ssid_len),
>  			             bss->ssid_len);
> 
> 
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