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Re: Off-by-one bug at unix_mkname ?

To: davem@xxxxxxxxxxxxx
Subject: Re: Off-by-one bug at unix_mkname ?
From: YOSHIFUJI Hideaki / 吉藤英明 <yoshfuji@xxxxxxxxxxxxxx>
Date: Mon, 28 Mar 2005 17:48:39 +0900 (JST)
Cc: linux-kernel@xxxxxxxxxxxxxxx, netdev@xxxxxxxxxxx, from-linux-kernel@xxxxxxxxxxxxxxxxxxx, yoshfuji@xxxxxxxxxxxxxx
In-reply-to: <20050328.173938.26746686.yoshfuji@xxxxxxxxxxxxxx>
Organization: USAGI Project
References: <200503281700.HHE91205.FtVLOStGOSPMYJFMN@xxxxxxxxxxxxxxxxxxx> <20050328.172108.30349253.yoshfuji@xxxxxxxxxxxxxx> <20050328.173938.26746686.yoshfuji@xxxxxxxxxxxxxx>
Sender: netdev-bounce@xxxxxxxxxxx
In article <20050328.173938.26746686.yoshfuji@xxxxxxxxxxxxxx> (at Mon, 28 Mar 
2005 17:39:38 +0900 (JST)), YOSHIFUJI Hideaki / 吉藤英明 <yoshfuji@xxxxxxxxxxxxxx> 
says:

> So, I'd suggest to put the comment back to 2.4/2.6 instead.
> (Note: net/socket.c refers this around MAX_SOCK_ADDR definition.)
> 
> Signed-off-by: Hideaki YOSHIFUJI <yoshfuji@xxxxxxxxxxxxxx>

Oops, sorry, I made a mistake when I did copy-n-paste...

Signed-off-by: Hideaki YOSHIFUJI <yoshfuji@xxxxxxxxxxxxxx>

===== net/unix/af_unix.c 1.73 vs edited =====
--- 1.73/net/unix/af_unix.c     2005-03-10 13:42:53 +09:00
+++ edited/net/unix/af_unix.c   2005-03-28 17:45:26 +09:00
@@ -188,6 +188,14 @@
        if (!sunaddr || sunaddr->sun_family != AF_UNIX)
                return -EINVAL;
        if (sunaddr->sun_path[0]) {
+               /*
+                *      This may look like an off by one error but it is
+                *      a bit more subtle. 108 is the longest valid AF_UNIX
+                *      path for a binding. sun_path[108] doesnt as such
+                *      exist. However in kernel space we are guaranteed that
+                *      it is a valid memory location in our kernel
+                *      address buffer.
+                */
                ((char *)sunaddr)[len]=0;
                len = strlen(sunaddr->sun_path)+1+sizeof(short);
                return len;

-- 
Hideaki YOSHIFUJI @ USAGI Project <yoshfuji@xxxxxxxxxxxxxx>
GPG FP: 9022 65EB 1ECF 3AD1 0BDF  80D8 4807 F894 E062 0EEA

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