RESEND: Re: [PATCH] unix domain sockets bugfix

[Balazs Scheidler]

hi,

final 2.4.20 still contains the recvfrom() bug I've sent you earlier.

----- Forwarded message from Balazs Scheidler <[e-mail]> -----

From: Balazs Scheidler <[e-mail]>
To: "David S. Miller" <[e-mail]>
Cc: [e-mail]
Subject: Re: [PATCH] unix domain sockets bugfix
Date: Tue, 5 Nov 2002 18:54:33 +0100

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.