[1878] in linux-net channel archive
general protection violation in sendmsg
daemon@ATHENA.MIT.EDU (Joerg Lenneis)
Wed Feb 7 14:37:06 1996
From: lenneis@statrix2.wu-wien.ac.at (Joerg Lenneis)
To: linux-net@vger.rutgers.edu
Date: Wed, 7 Feb 1996 19:46:45 +0100 (MET)
I think there is a bug somewhere in the implementation of the sendmsg system
call. I get the following error from the kernel (1.3.59 plus Mark 6 patches from
Alan Cox):
general protection: 0000
CPU: 0
EIP: 0010:[<001546da>]
EFLAGS: 00010212
eax: bffff7f4 ebx: bffff7f4 ecx: 00000000 edx: 00e1e60c
esi: 00e1e60c edi: 00000000 ebp: 00000000 esp: 00c7ae0c
ds: 0018 es: 0018 fs: 0018 gs: 002b ss: 0018
Process sender (pid: 102, process nr: 21, stackpage=00c7a000)
Stack: 0000002b 00e5a018 00c7aeb4 00000400 00000400 00000000 00e5a000 00e1e60c
00154837 00e1e60c 00e5a018 00000400 00000000 00000000 bffff7f4 00000010
00e1e60c 00000000 00000000 00000400 001567b1 00e1e60c 00c7aeb4 00000400
Call Trace: [<00154837>] [<001567b1>] [<00156700>] [<0013ca9b>] [<0013bca1>] [<0013d15a>] [<0015583a>]
[<0013c847>] [<0013cf9e>] [<0010abbe>]
Code: 66 8b 03 66 85 c0 74 06 66 83 f8 02 75 07 66 83 7b 02 00 75
This happens in the function udp_sendto in the code section
...........
if (usin)
{
if (addr_len < sizeof(sin))
return(-EINVAL);
if (usin->sin_family && usin->sin_family != AF_INET)
return(-EINVAL);
if (usin->sin_port == 0)
return(-EINVAL);
}
else
...........
usin is a struct sockaddr_in *. As soon as it is accessed in "if (usin)" the
error occurs. I have tried the same piece of code using the sendto system call
and that works, so I guess somewhere along the calling sequence something weird
happens to the usin argument. The following piece of source reproduces the error:
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/uio.h>
#include <stdlib.h>
#include <string.h>
#define BUFSIZE 128
main () {
struct sockaddr_in sa;
struct sockaddr_in ta;
char buf1[BUFSIZE];
char buf2[BUFSIZE];
int s;
struct msghdr msg;
struct iovec iov[2];
if (( s = socket ( AF_INET, SOCK_DGRAM, 0 )) < 0 ) {
perror ("socket");
exit(1);
}
bzero ( (char*) &sa, sizeof(sa));
sa.sin_family=AF_INET;
sa.sin_addr.s_addr= inet_addr("137.208.6.45");
sa.sin_port = htons(9998);
bzero ( (char*) &ta, sizeof(sa));
ta.sin_family=AF_INET;
ta.sin_addr.s_addr= inet_addr("137.208.6.33");
ta.sin_port = htons(9999);
if (bind(s, (struct sockaddr* )&sa, sizeof(sa))<0){
perror("bind");
exit(1);
}
msg.msg_name = (char *) &ta;
msg.msg_namelen = sizeof(ta);
msg.msg_iov = iov;
msg.msg_iovlen = 2;
msg.msg_accrights = NULL;
iov[0].iov_base = buf1;
iov[0].iov_len = BUFSIZE;
iov[1].iov_base = buf2;
iov[1].iov_len = BUFSIZE;
if(sendmsg(s, &msg, 0) < 0) {
perror ( "Sendmsg");
exit(1);
}
}
--
Joerg Lenneis
University of Economics and Business Adminstration
Department for Applied Statistics and Data Processing
Augasse 2-6, 1090 Vienna, Austria
Tel. *43/1/31336 4758
email: lenneis@wu-wien.ac.at
