Re: [PATCH] staging: rtl8712: prevent buffer overrun in recvbuf2recvframe

[Larry Finger <Larry.Finger@lwfinger.net>]

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On 05/19/2015 12:47 AM, Haggai Eran wrote:
> With an RTL8191SU USB adaptor, sometimes the hints for a fragmented
> packet are set, but the packet length is too large. Truncate the packet
> to prevent memory corruption.
>
> Signed-off-by: Haggai Eran <haggai.eran@gmail.com>
> ---
>
> Hi,
>
> I think this solves the issue for me. I'll test it more thoroughly later. I
> still don't know why a fragmented packet has such a large pkt_len value though.
>
> Thanks,
> Haggai
>
>   drivers/staging/rtl8712/rtl8712_recv.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)

I added a printout to your patch to log the values for tmp_len and alloc_sz when 
tmp_len > alloc_sz. In about 15 minutes of running, that print has not 
triggered. The condition only seems to happen on your system.

Please replace your patch with my modified version and report the printed values.

I have to go out today, thus there is no hurry.

Thanks,

Larry

>
> diff --git a/drivers/staging/rtl8712/rtl8712_recv.c b/drivers/staging/rtl8712/rtl8712_recv.c
> index cd8b444..d7ea9c1 100644
> --- a/drivers/staging/rtl8712/rtl8712_recv.c
> +++ b/drivers/staging/rtl8712/rtl8712_recv.c
> @@ -1055,8 +1055,12 @@ static int recvbuf2recvframe(struct _adapter *padapter, struct sk_buff *pskb)
>   		pkt_offset = (u16)round_up(tmp_len, 128);
>   		/* for first fragment packet, driver need allocate 1536 +
>   		 * drvinfo_sz + RXDESC_SIZE to defrag packet. */
> -		if ((mf == 1) && (frag == 0))
> +		if ((mf == 1) && (frag == 0)) {
>   			alloc_sz = 1658;/*1658+6=1664, 1664 is 128 alignment.*/
> +            if (tmp_len > alloc_sz) {
> +                tmp_len = alloc_sz;
> +            }
> +        }
>   		else
>   			alloc_sz = tmp_len;
>   		/* 2 is for IP header 4 bytes alignment in QoS packet case.
>


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From: Haggai Eran <haggai.eran@gmail.com>
To: Larry Finger <Larry.Finger@lwfinger.net>
Cc: linux-wireless@vger.kernel.org, Haggai Eran <haggai.eran@gmail.com>
Subject: [PATCH] staging: rtl8712: prevent buffer overrun in recvbuf2recvframe
Date: Tue, 19 May 2015 08:47:24 +0300
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With an RTL8191SU USB adaptor, sometimes the hints for a fragmented
packet are set, but the packet length is too large. Truncate the packet
to prevent memory corruption.

Signed-off-by: Haggai Eran <haggai.eran@gmail.com>
---

Hi,

I think this solves the issue for me. I'll test it more thoroughly later. I
still don't know why a fragmented packet has such a large pkt_len value though. 

Thanks,
Haggai

 drivers/staging/rtl8712/rtl8712_recv.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/rtl8712/rtl8712_recv.c b/drivers/staging/rtl8712/rtl8712_recv.c
index cd8b444..d7ea9c1 100644
--- a/drivers/staging/rtl8712/rtl8712_recv.c
+++ b/drivers/staging/rtl8712/rtl8712_recv.c
@@ -1055,8 +1055,12 @@ static int recvbuf2recvframe(struct _adapter *padapter, struct sk_buff *pskb)
 		pkt_offset = (u16)round_up(tmp_len, 128);
 		/* for first fragment packet, driver need allocate 1536 +
 		 * drvinfo_sz + RXDESC_SIZE to defrag packet. */
-		if ((mf == 1) && (frag == 0))
+		if ((mf == 1) && (frag == 0)) {
 			alloc_sz = 1658;/*1658+6=1664, 1664 is 128 alignment.*/
+            if (tmp_len > alloc_sz) {
+                tmp_len = alloc_sz;
+            }
+        }
 		else
 			alloc_sz = tmp_len;
 		/* 2 is for IP header 4 bytes alignment in QoS packet case.
-- 
1.9.1