[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: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Chris Wright <chrisw@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/include/net/compat.h b/include/net/compat.h
index 9983fd8..482eb82 100644 (file)
--- a/include/net/compat.h
+++ b/include/net/compat.h
@@ -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 */

diff --git a/net/compat.c b/net/compat.c
index d99ab96..e593dac 100644 (file)
--- a/net/compat.c
+++ b/net/compat.c
@@ -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);
        }
@@ -167,30 +169,34 @@ int cmsghdr_from_user_compat_to_kern(struct msghdr *kmsg,
         * until we have successfully copied over all of the data
         * from the user.
         */
-       if(kcmlen > stackbuf_size)
-               kcmsg_base = kcmsg = kmalloc(kcmlen, GFP_KERNEL);
-       if(kcmsg == NULL)
+       if (kcmlen > stackbuf_size)
+               kcmsg_base = kcmsg = sock_kmalloc(sk, kcmlen, GFP_KERNEL);
+       if (kcmsg == NULL)
                return -ENOBUFS;
 
        /* Now copy them over neatly. */
        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),
-                                 CMSG_COMPAT_DATA(ucmsg),
-                                 (ucmlen - CMSG_COMPAT_ALIGN(sizeof(*ucmsg)))))
-                       goto out_free_efault;
+               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 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:
-       if(kcmsg_base != (struct cmsghdr *)stackbuf)
-               kfree(kcmsg_base);
-       return -EFAULT;
+Einval:
+       err = -EINVAL;
+Efault:
+       if (kcmsg_base != (struct cmsghdr *)stackbuf)
+               sock_kfree_s(sk, kcmsg_base, kcmlen);
+       return err;
 }
 
 int put_cmsg_compat(struct msghdr *kmsg, int level, int type, int len, void *data)

diff --git a/net/socket.c b/net/socket.c
index e1bd5d8..c699e93 100644 (file)
--- a/net/socket.c
+++ b/net/socket.c
@@ -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))
                {