[NET]: Fix function put_cmsg() which may cause usr application memory overflow
When used function put_cmsg() to copy kernel information to user
application memory, if the memory length given by user application is
not enough, by the bad length calculate of msg.msg_controllen,
put_cmsg() function may cause the msg.msg_controllen to be a large
value, such as 0xFFFFFFF0, so the following put_cmsg() can also write
data to usr application memory even usr has no valid memory to store
this. This may cause usr application memory overflow.
int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data)
{
struct cmsghdr __user *cm
= (__force struct cmsghdr __user *)msg->msg_control;
struct cmsghdr cmhdr;
int cmlen = CMSG_LEN(len);
~~~~~~~~~~~~~~~~~~~~~
int err;
if (MSG_CMSG_COMPAT & msg->msg_flags)
return put_cmsg_compat(msg, level, type, len, data);
if (cm==NULL || msg->msg_controllen < sizeof(*cm)) {
msg->msg_flags |= MSG_CTRUNC;
return 0; /* XXX: return error? check spec. */
}
if (msg->msg_controllen < cmlen) {
~~~~~~~~~~~~~~~~~~~~~~~~
msg->msg_flags |= MSG_CTRUNC;
cmlen = msg->msg_controllen;
}
cmhdr.cmsg_level = level;
cmhdr.cmsg_type = type;
cmhdr.cmsg_len = cmlen;
err = -EFAULT;
if (copy_to_user(cm, &cmhdr, sizeof cmhdr))
goto out;
if (copy_to_user(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr)))
goto out;
cmlen = CMSG_SPACE(len);
~~~~~~~~~~~~~~~~~~~~~~~~~~~
If MSG_CTRUNC flags is set, msg->msg_controllen is less than
CMSG_SPACE(len), "msg->msg_controllen -= cmlen" will cause unsinged int
type msg->msg_controllen to be a large value.
~~~~~~~~~~~~~~~~~~~~~~~~~~~
msg->msg_control += cmlen;
msg->msg_controllen -= cmlen;
~~~~~~~~~~~~~~~~~~~~~
err = 0;
out:
return err;
}
The same promble exists in put_cmsg_compat(). This patch can fix this
problem.
Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/scm.c b/net/core/scm.c
index 100ba6d..10f5c65 100644
--- a/net/core/scm.c
+++ b/net/core/scm.c
@@ -196,6 +196,8 @@
if (copy_to_user(CMSG_DATA(cm), data, cmlen - sizeof(struct cmsghdr)))
goto out;
cmlen = CMSG_SPACE(len);
+ if (msg->msg_controllen < cmlen)
+ cmlen = msg->msg_controllen;
msg->msg_control += cmlen;
msg->msg_controllen -= cmlen;
err = 0;
