From 1ac70e7ad24a88710cf9b6d7ababaefa2b575df0 Mon Sep 17 00:00:00 2001 From: Wei Yongjun Date: Thu, 20 Dec 2007 14:36:44 -0800 Subject: [PATCH] [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 Signed-off-by: David S. Miller --- net/compat.c | 2 ++ net/core/scm.c | 2 ++ 2 files changed, 4 insertions(+) diff --git a/net/compat.c b/net/compat.c index d74d82155d78..377e560ab5c9 100644 --- a/net/compat.c +++ b/net/compat.c @@ -254,6 +254,8 @@ int put_cmsg_compat(struct msghdr *kmsg, int level, int type, int len, void *dat if (copy_to_user(CMSG_COMPAT_DATA(cm), data, cmlen - sizeof(struct compat_cmsghdr))) return -EFAULT; cmlen = CMSG_COMPAT_SPACE(len); + if (kmsg->msg_controllen < cmlen) + cmlen = kmsg->msg_controllen; kmsg->msg_control += cmlen; kmsg->msg_controllen -= cmlen; return 0; diff --git a/net/core/scm.c b/net/core/scm.c index 100ba6d9d478..10f5c65f6a47 100644 --- a/net/core/scm.c +++ b/net/core/scm.c @@ -196,6 +196,8 @@ int put_cmsg(struct msghdr * msg, int level, int type, int len, void *data) 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; -- 2.30.2