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List:       linux-kernel
Subject:    Re: [PATCH] unix domain sockets bugfix
From:       Balazs Scheidler <bazsi () balabit ! hu>
Date:       2002-11-05 17:54:33
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2.4.20-rc1, still not working well for recvfrom() of unix-dgram sockets. It
doesn't return 0 as the length of the sockaddr, checking out the code again
makes me think that this is the problem:

--- socket.c.old	Tue Nov  5 18:48:22 2002
+++ socket.c	Tue Nov  5 18:49:34 2002
@@ -1262,7 +1262,7 @@
 		flags |= MSG_DONTWAIT;
 	err=sock_recvmsg(sock, &msg, size, flags);
 
-	if(err >= 0 && addr != NULL && msg.msg_namelen)
+	if(err >= 0 && addr != NULL)
 	{
 		err2=move_addr_to_user(address, msg.msg_namelen, addr, addr_len);
 		if(err2<0)
---------

strace for the behaviour of the kernel:

> recvfrom(3, "<38>Nov  5 17:53:01 PAM_unix[952"..., 2048, 0, {sin_family=0xf80c /* \
> AF_??? */, {sa_family=63500, sa_data="\377\27 7\6\351\4\10\10\270\5\10\360@\5\10"}, \
> [256]) = 82

you can see that 256 is returned as the length of the sockaddr, and there's garbage \
in the sa_family field.

-- 
Bazsi
PGP info: KeyID 9AF8D0A9 Fingerprint CD27 CFB0 802C 0944 9CFD 804E C82C 8EB1
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