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net: Assert at build time the assumptions we make about the CMSG header.

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It must always be the case that CMSG_ALIGN(sizeof(hdr)) == sizeof(hdr).

Otherwise there are missing adjustments in the various calculations
that parse and build these things.

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2017-01-04 13:24:19 -05:00
parent 1ff8cebf49
commit ac4340fc3c
2 changed files with 5 additions and 0 deletions
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3
net/compat.c
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@ -130,6 +130,9 @@ int cmsghdr_from_user_compat_to_kern(struct msghdr *kmsg, struct sock *sk,
__kernel_size_t kcmlen, tmp;
int err = -EFAULT;
BUILD_BUG_ON(sizeof(struct compat_cmsghdr) !=
CMSG_COMPAT_ALIGN(sizeof(struct compat_cmsghdr)));
kcmlen = 0;
kcmsg_base = kcmsg = (struct cmsghdr *)stackbuf;
ucmsg = CMSG_COMPAT_FIRSTHDR(kmsg);

2
net/socket.c
View File

@ -1948,6 +1948,8 @@ static int ___sys_sendmsg(struct socket *sock, struct user_msghdr __user *msg,
ctl_buf = msg_sys->msg_control;
ctl_len = msg_sys->msg_controllen;
} else if (ctl_len) {
BUILD_BUG_ON(sizeof(struct cmsghdr) !=
CMSG_ALIGN(sizeof(struct cmsghdr)));
if (ctl_len > sizeof(ctl)) {
ctl_buf = sock_kmalloc(sock->sk, ctl_len, GFP_KERNEL);
if (ctl_buf == NULL)