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authorWeiping Pan <wpan@redhat.com>2012-07-23 10:37:48 +0800
committerDavid S. Miller <davem@davemloft.net>2012-07-23 01:01:44 -0700
commit06b6a1cf6e776426766298d055bb3991957d90a7 (patch)
tree516f0dbc5c54033a0a6fa66f7c2a813dc338a787 /net/rds/recv.c
parent5b3e7e6cb5771bedda51cdb6f715d1da8cd9e644 (diff)
downloadlinux-stericsson-06b6a1cf6e776426766298d055bb3991957d90a7.tar.gz
rds: set correct msg_namelen
Jay Fenlason (fenlason@redhat.com) found a bug, that recvfrom() on an RDS socket can return the contents of random kernel memory to userspace if it was called with a address length larger than sizeof(struct sockaddr_in). rds_recvmsg() also fails to set the addr_len paramater properly before returning, but that's just a bug. There are also a number of cases wher recvfrom() can return an entirely bogus address. Anything in rds_recvmsg() that returns a non-negative value but does not go through the "sin = (struct sockaddr_in *)msg->msg_name;" code path at the end of the while(1) loop will return up to 128 bytes of kernel memory to userspace. And I write two test programs to reproduce this bug, you will see that in rds_server, fromAddr will be overwritten and the following sock_fd will be destroyed. Yes, it is the programmer's fault to set msg_namelen incorrectly, but it is better to make the kernel copy the real length of address to user space in such case. How to run the test programs ? I test them on 32bit x86 system, 3.5.0-rc7. 1 compile gcc -o rds_client rds_client.c gcc -o rds_server rds_server.c 2 run ./rds_server on one console 3 run ./rds_client on another console 4 you will see something like: server is waiting to receive data... old socket fd=3 server received data from client:data from client msg.msg_namelen=32 new socket fd=-1067277685 sendmsg() : Bad file descriptor /***************** rds_client.c ********************/ int main(void) { int sock_fd; struct sockaddr_in serverAddr; struct sockaddr_in toAddr; char recvBuffer[128] = "data from client"; struct msghdr msg; struct iovec iov; sock_fd = socket(AF_RDS, SOCK_SEQPACKET, 0); if (sock_fd < 0) { perror("create socket error\n"); exit(1); } memset(&serverAddr, 0, sizeof(serverAddr)); serverAddr.sin_family = AF_INET; serverAddr.sin_addr.s_addr = inet_addr("127.0.0.1"); serverAddr.sin_port = htons(4001); if (bind(sock_fd, (struct sockaddr*)&serverAddr, sizeof(serverAddr)) < 0) { perror("bind() error\n"); close(sock_fd); exit(1); } memset(&toAddr, 0, sizeof(toAddr)); toAddr.sin_family = AF_INET; toAddr.sin_addr.s_addr = inet_addr("127.0.0.1"); toAddr.sin_port = htons(4000); msg.msg_name = &toAddr; msg.msg_namelen = sizeof(toAddr); msg.msg_iov = &iov; msg.msg_iovlen = 1; msg.msg_iov->iov_base = recvBuffer; msg.msg_iov->iov_len = strlen(recvBuffer) + 1; msg.msg_control = 0; msg.msg_controllen = 0; msg.msg_flags = 0; if (sendmsg(sock_fd, &msg, 0) == -1) { perror("sendto() error\n"); close(sock_fd); exit(1); } printf("client send data:%s\n", recvBuffer); memset(recvBuffer, '\0', 128); msg.msg_name = &toAddr; msg.msg_namelen = sizeof(toAddr); msg.msg_iov = &iov; msg.msg_iovlen = 1; msg.msg_iov->iov_base = recvBuffer; msg.msg_iov->iov_len = 128; msg.msg_control = 0; msg.msg_controllen = 0; msg.msg_flags = 0; if (recvmsg(sock_fd, &msg, 0) == -1) { perror("recvmsg() error\n"); close(sock_fd); exit(1); } printf("receive data from server:%s\n", recvBuffer); close(sock_fd); return 0; } /***************** rds_server.c ********************/ int main(void) { struct sockaddr_in fromAddr; int sock_fd; struct sockaddr_in serverAddr; unsigned int addrLen; char recvBuffer[128]; struct msghdr msg; struct iovec iov; sock_fd = socket(AF_RDS, SOCK_SEQPACKET, 0); if(sock_fd < 0) { perror("create socket error\n"); exit(0); } memset(&serverAddr, 0, sizeof(serverAddr)); serverAddr.sin_family = AF_INET; serverAddr.sin_addr.s_addr = inet_addr("127.0.0.1"); serverAddr.sin_port = htons(4000); if (bind(sock_fd, (struct sockaddr*)&serverAddr, sizeof(serverAddr)) < 0) { perror("bind error\n"); close(sock_fd); exit(1); } printf("server is waiting to receive data...\n"); msg.msg_name = &fromAddr; /* * I add 16 to sizeof(fromAddr), ie 32, * and pay attention to the definition of fromAddr, * recvmsg() will overwrite sock_fd, * since kernel will copy 32 bytes to userspace. * * If you just use sizeof(fromAddr), it works fine. * */ msg.msg_namelen = sizeof(fromAddr) + 16; /* msg.msg_namelen = sizeof(fromAddr); */ msg.msg_iov = &iov; msg.msg_iovlen = 1; msg.msg_iov->iov_base = recvBuffer; msg.msg_iov->iov_len = 128; msg.msg_control = 0; msg.msg_controllen = 0; msg.msg_flags = 0; while (1) { printf("old socket fd=%d\n", sock_fd); if (recvmsg(sock_fd, &msg, 0) == -1) { perror("recvmsg() error\n"); close(sock_fd); exit(1); } printf("server received data from client:%s\n", recvBuffer); printf("msg.msg_namelen=%d\n", msg.msg_namelen); printf("new socket fd=%d\n", sock_fd); strcat(recvBuffer, "--data from server"); if (sendmsg(sock_fd, &msg, 0) == -1) { perror("sendmsg()\n"); close(sock_fd); exit(1); } } close(sock_fd); return 0; } Signed-off-by: Weiping Pan <wpan@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/rds/recv.c')
-rw-r--r--net/rds/recv.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/net/rds/recv.c b/net/rds/recv.c
index 5c6e9f132026..9f0f17cf6bf9 100644
--- a/net/rds/recv.c
+++ b/net/rds/recv.c
@@ -410,6 +410,8 @@ int rds_recvmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *msg,
rdsdebug("size %zu flags 0x%x timeo %ld\n", size, msg_flags, timeo);
+ msg->msg_namelen = 0;
+
if (msg_flags & MSG_OOB)
goto out;
@@ -485,6 +487,7 @@ int rds_recvmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *msg,
sin->sin_port = inc->i_hdr.h_sport;
sin->sin_addr.s_addr = inc->i_saddr;
memset(sin->sin_zero, 0, sizeof(sin->sin_zero));
+ msg->msg_namelen = sizeof(*sin);
}
break;
}