From: Weiping Pan <wpan@xxxxxxxxxx>
-------------------
This is a commit scheduled for the next v2.6.34 longterm release.
http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git
If you see a problem with using this for longterm, please comment.
-------------------
commit 06b6a1cf6e776426766298d055bb3991957d90a7 upstream.
Jay Fenlason (fenlason@xxxxxxxxxx) 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@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
---
net/rds/recv.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/net/rds/recv.c b/net/rds/recv.c
index 93aadc0173cb..de4d79c56662 100644
--- a/net/rds/recv.c
+++ b/net/rds/recv.c
@@ -411,6 +411,8 @@ 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;
@@ -486,6 +488,7 @@ 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;
}
--
1.8.5.2
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