Commit 8920e8f9 authored by Al Viro's avatar Al Viro Committed by Linus Torvalds
Browse files

[PATCH] Fix 32bit sendmsg() flaw 



When we copy 32bit ->msg_control contents to kernel, we walk the same
userland data twice without sanity checks on the second pass.

Second version of this patch: the original broke with 64-bit arches
running 32-bit-compat-mode executables doing sendmsg() syscalls with
unaligned CMSG data areas

Another thing is that we use kmalloc() to allocate and sock_kfree_s()
to free afterwards; less serious, but also needs fixing.

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarDavid Woodhouse <dwmw2@infradead.org>
Signed-off-by: default avatarChris Wright <chrisw@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 5aa3b610

include/net/compat.h

+1 −1
Original line number Diff line number Diff line
@@ -33,7 +33,7 @@ extern asmlinkage long compat_sys_sendmsg(int,struct compat_msghdr __user *,unsi 
extern asmlinkage long compat_sys_recvmsg(int,struct compat_msghdr __user *,unsigned);

extern asmlinkage long compat_sys_getsockopt(int, int, int, char __user *, int __user *);

extern int put_cmsg_compat(struct msghdr*, int, int, int, void *);

extern int cmsghdr_from_user_compat_to_kern(struct msghdr *, unsigned char *,

extern int cmsghdr_from_user_compat_to_kern(struct msghdr *, struct sock *, unsigned char *,

		int);



#endif /* NET_COMPAT_H */

net/compat.c

+26 −18
Original line number Diff line number Diff line
@@ -135,13 +135,14 @@ static inline struct compat_cmsghdr __user *cmsg_compat_nxthdr(struct msghdr *ms 
 * thus placement) of cmsg headers and length are different for

 * 32-bit apps.  -DaveM

 */

int cmsghdr_from_user_compat_to_kern(struct msghdr *kmsg,

int cmsghdr_from_user_compat_to_kern(struct msghdr *kmsg, struct sock *sk,

			       unsigned char *stackbuf, int stackbuf_size)

{

	struct compat_cmsghdr __user *ucmsg;

	struct cmsghdr *kcmsg, *kcmsg_base;

	compat_size_t ucmlen;

	__kernel_size_t kcmlen, tmp;

	int err = -EFAULT;



	kcmlen = 0;

	kcmsg_base = kcmsg = (struct cmsghdr *)stackbuf;
@@ -156,6 +157,7 @@ int cmsghdr_from_user_compat_to_kern(struct msghdr *kmsg, 


		tmp = ((ucmlen - CMSG_COMPAT_ALIGN(sizeof(*ucmsg))) +

		       CMSG_ALIGN(sizeof(struct cmsghdr)));

		tmp = CMSG_ALIGN(tmp);

		kcmlen += tmp;

		ucmsg = cmsg_compat_nxthdr(kmsg, ucmsg, ucmlen);

	}
@@ -168,7 +170,7 @@ int cmsghdr_from_user_compat_to_kern(struct msghdr *kmsg, 
	 * from the user.

	 */

	if (kcmlen > stackbuf_size)

		kcmsg_base = kcmsg = kmalloc(kcmlen, GFP_KERNEL);

		kcmsg_base = kcmsg = sock_kmalloc(sk, kcmlen, GFP_KERNEL);

	if (kcmsg == NULL)

		return -ENOBUFS;
@@ -176,21 +178,25 @@ int cmsghdr_from_user_compat_to_kern(struct msghdr *kmsg, 
	memset(kcmsg, 0, kcmlen);

	ucmsg = CMSG_COMPAT_FIRSTHDR(kmsg);

	while(ucmsg != NULL) {

		__get_user(ucmlen, &ucmsg->cmsg_len);

		if (__get_user(ucmlen, &ucmsg->cmsg_len))

			goto Efault;

		if (!CMSG_COMPAT_OK(ucmlen, ucmsg, kmsg))

			goto Einval;

		tmp = ((ucmlen - CMSG_COMPAT_ALIGN(sizeof(*ucmsg))) +

		       CMSG_ALIGN(sizeof(struct cmsghdr)));

		if ((char *)kcmsg_base + kcmlen - (char *)kcmsg < CMSG_ALIGN(tmp))

			goto Einval;

		kcmsg->cmsg_len = tmp;

		__get_user(kcmsg->cmsg_level, &ucmsg->cmsg_level);

		__get_user(kcmsg->cmsg_type, &ucmsg->cmsg_type);



		/* Copy over the data. */

		if(copy_from_user(CMSG_DATA(kcmsg),

		tmp = CMSG_ALIGN(tmp);

		if (__get_user(kcmsg->cmsg_level, &ucmsg->cmsg_level) ||

		    __get_user(kcmsg->cmsg_type, &ucmsg->cmsg_type) ||

		    copy_from_user(CMSG_DATA(kcmsg),

				   CMSG_COMPAT_DATA(ucmsg),

				   (ucmlen - CMSG_COMPAT_ALIGN(sizeof(*ucmsg)))))

			goto out_free_efault;

			goto Efault;



		/* Advance. */

		kcmsg = (struct cmsghdr *)((char *)kcmsg + CMSG_ALIGN(tmp));

		kcmsg = (struct cmsghdr *)((char *)kcmsg + tmp);

		ucmsg = cmsg_compat_nxthdr(kmsg, ucmsg, ucmlen);

	}
@@ -199,10 +205,12 @@ int cmsghdr_from_user_compat_to_kern(struct msghdr *kmsg, 
	kmsg->msg_controllen = kcmlen;

	return 0;



out_free_efault:

Einval:

	err = -EINVAL;

Efault:

	if (kcmsg_base != (struct cmsghdr *)stackbuf)

		kfree(kcmsg_base);

	return -EFAULT;

		sock_kfree_s(sk, kcmsg_base, kcmlen);

	return err;

}



int put_cmsg_compat(struct msghdr *kmsg, int level, int type, int len, void *data)

net/socket.c

+2 −1
Original line number Diff line number Diff line
@@ -1745,10 +1745,11 @@ asmlinkage long sys_sendmsg(int fd, struct msghdr __user *msg, unsigned flags) 
		goto out_freeiov;

	ctl_len = msg_sys.msg_controllen; 

	if ((MSG_CMSG_COMPAT & flags) && ctl_len) {

		err = cmsghdr_from_user_compat_to_kern(&msg_sys, ctl, sizeof(ctl));

		err = cmsghdr_from_user_compat_to_kern(&msg_sys, sock->sk, ctl, sizeof(ctl));

		if (err)

			goto out_freeiov;

		ctl_buf = msg_sys.msg_control;

		ctl_len = msg_sys.msg_controllen;

	} else if (ctl_len) {

		if (ctl_len > sizeof(ctl))

		{

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