[277/289] econet: fix CVE-2010-3848

Greg KH
2010-12-08T01:07:20Z

From: Phil Blundell <philb@gnu.org>

commit a27e13d370415add3487949c60810e36069a23a6 upstream.

Don't declare variable sized array of iovecs on the stack since this
could cause stack overflow if msg->msgiovlen is large. Instead, coalesce
the user-supplied data into a new buffer and use a single iovec for it.

Signed-off-by: Phil Blundell <philb@gnu.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
net/econet/af_econet.c | 62 ++++++++++++++++++++++++-------------------------
1 file changed, 31 insertions(+), 31 deletions(-)

--- a/net/econet/af_econet.c
+++ b/net/econet/af_econet.c
@@ -31,6 +31,7 @@
#include <linux/skbuff.h>
#include <linux/udp.h>
#include <linux/slab.h>
+#include <linux/vmalloc.h>
#include <net/sock.h>
#include <net/inet_common.h>
#include <linux/stat.h>
@@ -276,12 +277,12 @@ static int econet_sendmsg(struct kiocb *
#endif
#ifdef CONFIG_ECONET_AUNUDP
struct msghdr udpmsg;
- struct iovec iov[msg->msg_iovlen+1];
+ struct iovec iov[2];
struct aunhdr ah;
struct sockaddr_in udpdest;
__kernel_size_t size;
- int i;
mm_segment_t oldfs;
+ char *userbuf;
#endif

/*
@@ -319,17 +320,17 @@ static int econet_sendmsg(struct kiocb *
}
}

- if (len + 15 > dev->mtu) {
- mutex_unlock(&econet_mutex);
- return -EMSGSIZE;
- }
-
if (dev->type == ARPHRD_ECONET) {
/* Real hardware Econet. We're not worthy etc. */
#ifdef CONFIG_ECONET_NATIVE
unsigned short proto = 0;
int res;

+ if (len + 15 > dev->mtu) {
+ mutex_unlock(&econet_mutex);
+ return -EMSGSIZE;
+ }
+
dev_hold(dev);

skb = sock_alloc_send_skb(sk, len+LL_ALLOCATED_SPACE(dev),
@@ -405,6 +406,11 @@ static int econet_sendmsg(struct kiocb *
return -ENETDOWN; /* No socket - can't send */
}

+ if (len > 32768) {
+ err = -E2BIG;
+ goto error;
+ }
+
/* Make up a UDP datagram and hand it off to some higher intellect. */

memset(&udpdest, 0, sizeof(udpdest));
@@ -436,36 +442,26 @@ static int econet_sendmsg(struct kiocb *

/* tack our header on the front of the iovec */
size = sizeof(struct aunhdr);
- /*
- * XXX: that is b0rken. We can't mix userland and kernel pointers
- * in iovec, since on a lot of platforms copy_from_user() will
- * *not* work with the kernel and userland ones at the same time,
- * regardless of what we do with set_fs(). And we are talking about
- * econet-over-ethernet here, so "it's only ARM anyway" doesn't
- * apply. Any suggestions on fixing that code? -- AV
- */
iov[0].iov_base = (void *)&ah;
iov[0].iov_len = size;
- for (i = 0; i < msg->msg_iovlen; i++) {
- void __user *base = msg->msg_iov[i].iov_base;
- size_t iov_len = msg->msg_iov[i].iov_len;
- /* Check it now since we switch to KERNEL_DS later. */
- if (!access_ok(VERIFY_READ, base, iov_len)) {
- mutex_unlock(&econet_mutex);
- return -EFAULT;
- }
- iov[i+1].iov_base = base;
- iov[i+1].iov_len = iov_len;
- size += iov_len;
+
+ userbuf = vmalloc(len);
+ if (userbuf == NULL) {
+ err = -ENOMEM;
+ goto error;
}

+ iov[1].iov_base = userbuf;
+ iov[1].iov_len = len;
+ err = memcpy_fromiovec(userbuf, msg->msg_iov, len);
+ if (err)
+ goto error_free_buf;
+
/* Get a skbuff (no data, just holds our cb information) */
if ((skb = sock_alloc_send_skb(sk, 0,
msg->msg_flags & MSG_DONTWAIT,
- &err)) == NULL) {
- mutex_unlock(&econet_mutex);
- return err;
- }
+ &err)) == NULL)
+ goto error_free_buf;

eb = (struct ec_cb *)&skb->cb;

@@ -481,7 +477,7 @@ static int econet_sendmsg(struct kiocb *
udpmsg.msg_name = (void *)&udpdest;
udpmsg.msg_namelen = sizeof(udpdest);
udpmsg.msg_iov = &iov[0];
- udpmsg.msg_iovlen = msg->msg_iovlen + 1;
+ udpmsg.msg_iovlen = 2;
udpmsg.msg_control = NULL;
udpmsg.msg_controllen = 0;
udpmsg.msg_flags=0;
@@ -489,9 +485,13 @@ static int econet_sendmsg(struct kiocb *
oldfs = get_fs(); set_fs(KERNEL_DS); /* More privs :-) */
err = sock_sendmsg(udpsock, &udpmsg, size);
set_fs(oldfs);
+
+error_free_buf:
+ vfree(userbuf);
#else
err = -EPROTOTYPE;
#endif
+ error:
mutex_unlock(&econet_mutex);

return err;