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

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

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On 05/20/2015 01:17 AM, Haggai Eran wrote:
> On May 19, 2015 08:47, "Haggai Eran" <haggai.eran@gmail.com
> <mailto:haggai.eran@gmail.com>> 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 <mailto: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
>  >
>
> I guess I was too quick with this patch. It prevents the kernel page faults, but
> with it I still see sometimes the connectivity disappear for a minute or two.

Is anything logged when that happens?

I'm still trying to see where that magic number of 1658 comes from, and how that 
affects the RX buffer size.

When I unconditionally set alloc_sz to tmp_len as in the attached patch (I 
remembered to refresh it this time), nothing bad has happened here yet. What 
happens on your box?

Larry



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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(-)

Index: wireless-drivers-next/drivers/staging/rtl8712/rtl8712_recv.c
===================================================================
--- wireless-drivers-next.orig/drivers/staging/rtl8712/rtl8712_recv.c
+++ wireless-drivers-next/drivers/staging/rtl8712/rtl8712_recv.c
@@ -1053,12 +1053,7 @@ static int recvbuf2recvframe(struct _ada
 		precvframe->u.hdr.len = 0;
 		tmp_len = pkt_len + drvinfo_sz + RXDESC_SIZE;
 		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))
-			alloc_sz = 1658;/*1658+6=1664, 1664 is 128 alignment.*/
-		else
-			alloc_sz = tmp_len;
+		alloc_sz = tmp_len;
 		/* 2 is for IP header 4 bytes alignment in QoS packet case.
 		 * 4 is for skb->data 4 bytes alignment. */
 		alloc_sz += 6;