Re: Bug in Guile's Posix Networking

[Noah Lavine <noah.b.lavine@gmail.com>]

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Hello again,

The attached patch fixes the problem for me, and I believe zeroing
some data structures before they're used won't hurt things for anyone
else.

Noah

On Sat, Feb 12, 2011 at 8:45 PM, Noah Lavine <noah.b.lavine@gmail.com> wrote:
> Hi all,
>
> I think I have isolated the error (although in fact there are two
> things that should be fixed).
>
> I gdb'd Guile's executable and looked at the struct sockaddr just
> before it was passed to bind. There were two mistakes.
>
> First of all, that struct has an sa_len field which is supposed to
> contain its length, but in fact contained junk. Second of all, it
> should have been padded with 8 bytes of zeros at the end, but it
> wasn't. After experimenting a bit, it turns out that padding with
> zeros was what made the difference, but probably the sa_len field
> should be fixed anyway. I'll work on a patch for this.
>
> Noah
>
> On Sat, Feb 12, 2011 at 8:22 PM, Noah Lavine <noah.b.lavine@gmail.com> wrote:
>> Hi,
>>
>>> #x49 is 73 :)
>>
>> If I knew a facepalm emoticon, I would use it now. :)
>>
>>> Could the lseek could be the problem?
>>
>> Maybe, but I suspect not. My man page for lseek says that lseek will
>> fail with ESPIPE if it is called on a socket, and my errno.h defines
>> ESPIPE to be 29, which is the error we got. So that's what's happening
>> there.
>>
>> However, I looked to see where the lseek call was coming from, and it
>> happens in scm_fdes_to_port, on line 564 of fports.c. The lseek is
>> done for the purpose of checking whether the port supports lseek, and
>> when it returns -1, we put an entry into some data structure (port
>> table?) saying that it doesn't support random access. So it looks like
>> that error is actually expected in the port code.
>>
>> Noah
>>
>

[-- Attachment #2: 0001-libguile-socket.c-fix-use-of-uninitialized-memory.patch --]
[-- Type: application/octet-stream, Size: 1126 bytes --]

From 6daec8ce9ecc4784a42479d1ad101435a0408ecf Mon Sep 17 00:00:00 2001
From: Noah Lavine <nlavine@haverford.edu>
Date: Sat, 12 Feb 2011 21:05:34 -0500
Subject: [PATCH]  * libguile/socket.c: fix use of uninitialized memory.

---
 libguile/socket.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/libguile/socket.c b/libguile/socket.c
index aa52cac..d8ab005 100644
--- a/libguile/socket.c
+++ b/libguile/socket.c
@@ -796,6 +796,7 @@ scm_fill_sockaddr (int fam, SCM address, SCM *args, int which_arg,
 	port = scm_to_int (SCM_CAR (*args));
 	*args = SCM_CDR (*args);
 	soka = (struct sockaddr_in *) scm_malloc (sizeof (struct sockaddr_in));
+        memset (soka, '\0', sizeof (struct sockaddr_in));
 
 #ifdef HAVE_STRUCT_SOCKADDR_SIN_LEN
 	soka->sin_len = sizeof (struct sockaddr_in);
@@ -1131,6 +1132,8 @@ scm_to_sockaddr (SCM address, size_t *address_size)
 	  {
 	    struct sockaddr_in c_inet;
 
+            memset (&c_inet, '\0', sizeof (struct sockaddr_in));
+
 	    c_inet.sin_addr.s_addr =
 	      htonl (scm_to_ulong (SCM_SIMPLE_VECTOR_REF (address, 1)));
 	    c_inet.sin_port =
-- 
1.7.4