Fix denial of service - memory corruption.

CVE-2011-0719

Fix bug #7949 (DoS in Winbind and smbd with many file descriptors open).

All current released versions of Samba are vulnerable to
a denial of service caused by memory corruption. Range
checks on file descriptors being used in the FD_SET macro
were not present allowing stack corruption. This can cause
the Samba code to crash or to loop attempting to select
on a bad file descriptor set.

A connection to a file share, or a local account is needed
to exploit this problem, either authenticated or unauthenticated
(guest connection).

Currently we do not believe this flaw is exploitable
beyond a crash or causing the code to loop, but on the
advice of our security reviewers we are releasing fixes
in case an exploit is discovered at a later date.

1 files changed, 9 insertions, 2 deletions

diff --git a/source/lib/util_sock.c b/source/lib/util_sock.c
index 650bd1302f8..8aa2c97f235 100644
--- a/source/lib/util_sock.c
+++ b/source/lib/util_sock.c
@@ -960,6 +960,11 @@ NTSTATUS read_socket_with_timeout(int fd, char *buf,
 	timeout.tv_usec = (long)(1000 * (time_out % 1000));
 
 	for (nread=0; nread < mincnt; ) {
+		if (fd < 0 || fd >= FD_SETSIZE) {
+			errno = EBADF;
+			return map_nt_error_from_unix(EBADF);
+		}
+
 		FD_ZERO(&fds);
 		FD_SET(fd,&fds);
 
@@ -1492,7 +1497,7 @@ bool open_any_socket_out(struct sockaddr_storage *addrs, int num_addrs,
 
 	for (i=0; i<num_addrs; i++) {
 		sockets[i] = socket(addrs[i].ss_family, SOCK_STREAM, 0);
-		if (sockets[i] < 0)
+		if (sockets[i] < 0 || sockets[i] >= FD_SETSIZE)
 			goto done;
 		set_blocking(sockets[i], false);
 	}
@@ -1541,8 +1546,10 @@ bool open_any_socket_out(struct sockaddr_storage *addrs, int num_addrs,
 	FD_ZERO(&r_fds);
 
 	for (i=0; i<num_addrs; i++) {
-		if (sockets[i] == -1)
+		if (sockets[i] < 0 || sockets[i] >= FD_SETSIZE) {
+			/* This cannot happen - ignore if so. */
 			continue;
+		}
 		FD_SET(sockets[i], &wr_fds);
 		FD_SET(sockets[i], &r_fds);
 		if (sockets[i]>maxfd)