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, 17 insertions, 0 deletions

diff --git a/nsswitch/wb_common.c b/nsswitch/wb_common.c
index d0dfcb8bbfb..75ce585a863 100644
--- a/nsswitch/wb_common.c
+++ b/nsswitch/wb_common.c
@@ -240,6 +240,12 @@ static int winbind_named_pipe_sock(const char *dir)
 
 		switch (errno) {
 			case EINPROGRESS:
+
+				if (fd < 0 || fd >= FD_SETSIZE) {
+					errno = EBADF;
+					goto error_out;
+				}
+
 				FD_ZERO(&w_fds);
 				FD_SET(fd, &w_fds);
 				tv.tv_sec = CONNECT_TIMEOUT - wait_time;
@@ -384,6 +390,12 @@ int winbind_write_sock(void *buffer, int count, int recursing, int need_priv)
 		struct timeval tv;
 		fd_set r_fds;
 
+		if (winbindd_fd < 0 || winbindd_fd >= FD_SETSIZE) {
+			errno = EBADF;
+			winbind_close_sock();
+			return -1;
+		}
+
 		/* Catch pipe close on other end by checking if a read()
 		   call would not block by calling select(). */
 
@@ -444,6 +456,11 @@ int winbind_read_sock(void *buffer, int count)
 		struct timeval tv;
 		fd_set r_fds;
 
+		if (winbindd_fd < 0 || winbindd_fd >= FD_SETSIZE) {
+			errno = EBADF;
+			winbind_close_sock();
+			return -1;
+		}
 		/* Catch pipe close on other end by checking if a read()
 		   call would not block by calling select(). */