net: Limit socket I/O iovec total length to INT_MAX.

commit 8acfe468b0384e834a303f08ebc4953d72fb690a upstream.

This helps protect us from overflow issues down in the
individual protocol sendmsg/recvmsg handlers.  Once
we hit INT_MAX we truncate out the rest of the iovec
by setting the iov_len members to zero.

This works because:

1) For SOCK_STREAM and SOCK_SEQPACKET sockets, partial
   writes are allowed and the application will just continue
   with another write to send the rest of the data.

2) For datagram oriented sockets, where there must be a
   one-to-one correspondance between write() calls and
   packets on the wire, INT_MAX is going to be far larger
   than the packet size limit the protocol is going to
   check for and signal with -EMSGSIZE.

Based upon a patch by Linus Torvalds.

Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/include/linux/socket.h b/include/linux/socket.h
index 1b5034a58544cbed6cad48fcdd5406df614c89cd..354cc5617f8b87304b97eebeec2c4b3e8a52428a 100644 (file)
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -314,7 +314,7 @@ extern int csum_partial_copy_fromiovecend(unsigned char *kdata,
                                          int offset, 
                                          unsigned int len, __wsum *csump);
 
-extern long verify_iovec(struct msghdr *m, struct iovec *iov, struct sockaddr *address, int mode);
+extern int verify_iovec(struct msghdr *m, struct iovec *iov, struct sockaddr *address, int mode);
 extern int memcpy_toiovec(struct iovec *v, unsigned char *kdata, int len);
 extern int memcpy_toiovecend(const struct iovec *v, unsigned char *kdata,
                             int offset, int len);

diff --git a/net/compat.c b/net/compat.c
index ec24d9edb0258ecda760deaf80eaa211f844feef..b8695349e40ef0bb35c4c0802baa0085e086f5aa 100644 (file)
--- a/net/compat.c
+++ b/net/compat.c
@@ -41,10 +41,12 @@ static inline int iov_from_user_compat_to_kern(struct iovec *kiov,
                compat_size_t len;
 
                if (get_user(len, &uiov32->iov_len) ||
-                  get_user(buf, &uiov32->iov_base)) {
-                       tot_len = -EFAULT;
-                       break;
-               }
+                   get_user(buf, &uiov32->iov_base))
+                       return -EFAULT;
+
+               if (len > INT_MAX - tot_len)
+                       len = INT_MAX - tot_len;
+
                tot_len += len;
                kiov->iov_base = compat_ptr(buf);
                kiov->iov_len = (__kernel_size_t) len;

diff --git a/net/core/iovec.c b/net/core/iovec.c
index b5b28f093b1c2aeddc32b51ea4ee1b1e08b3a555..16ed5844ae0fd6f8501ecf73bc9eef0dee55f193 100644 (file)
--- a/net/core/iovec.c
+++ b/net/core/iovec.c
@@ -35,10 +35,9 @@
  *     in any case.
  */
 
-long verify_iovec(struct msghdr *m, struct iovec *iov, struct sockaddr *address, int mode)
+int verify_iovec(struct msghdr *m, struct iovec *iov, struct sockaddr *address, int mode)
 {
-       int size, ct;
-       long err;
+       int size, ct, err;
 
        if (m->msg_namelen) {
                if (mode == VERIFY_READ) {
@@ -60,14 +59,13 @@ long verify_iovec(struct msghdr *m, struct iovec *iov, struct sockaddr *address,
        err = 0;
 
        for (ct = 0; ct < m->msg_iovlen; ct++) {
-               err += iov[ct].iov_len;
-               /*
-                * Goal is not to verify user data, but to prevent returning
-                * negative value, which is interpreted as errno.
-                * Overflow is still possible, but it is harmless.
-                */
-               if (err < 0)
-                       return -EMSGSIZE;
+               size_t len = iov[ct].iov_len;
+
+               if (len > INT_MAX - err) {
+                       len = INT_MAX - err;
+                       iov[ct].iov_len = len;
+               }
+               err += len;
        }
 
        return err;