From 2eecc8afd02d8c65cf098cbae4de87f332dc21bd Mon Sep 17 00:00:00 2001 From: Florian Weimer Date: Mon, 9 Nov 2015 12:48:41 +0100 Subject: Terminate process on invalid netlink response from kernel [BZ #12926] The recvmsg system calls for netlink sockets have been particularly prone to picking up unrelated data after a file descriptor race (where the descriptor is closed and reopened concurrently in a multi-threaded process, as the result of a file descriptor management issue elsewhere). This commit adds additional error checking and aborts the process if a datagram of unexpected length (without the netlink header) is received, or an error code which cannot happen due to the way the netlink socket is used. [BZ #12926] Terminate process on invalid netlink response. * sysdeps/unix/sysv/linux/netlinkaccess.h (__netlink_assert_response): Declare. * sysdeps/unix/sysv/linux/netlink_assert_response.c: New file. * sysdeps/unix/sysv/linux/Makefile [$(subdir) == inet] (sysdep_routines): Add netlink_assert_response. * sysdeps/unix/sysv/linux/check_native.c (__check_native): Call __netlink_assert_response. * sysdeps/unix/sysv/linux/check_pf.c (make_request): Likewise. * sysdeps/unix/sysv/linux/ifaddrs.c (__netlink_request): Likewise. * sysdeps/unix/sysv/linux/Versions (GLIBC_PRIVATE): Add __netlink_assert_response. --- sysdeps/unix/sysv/linux/Makefile | 1 + sysdeps/unix/sysv/linux/Versions | 2 + sysdeps/unix/sysv/linux/check_native.c | 2 + sysdeps/unix/sysv/linux/check_pf.c | 4 +- sysdeps/unix/sysv/linux/ifaddrs.c | 1 + sysdeps/unix/sysv/linux/netlink_assert_response.c | 106 ++++++++++++++++++++++ sysdeps/unix/sysv/linux/netlinkaccess.h | 6 ++ 7 files changed, 121 insertions(+), 1 deletion(-) create mode 100644 sysdeps/unix/sysv/linux/netlink_assert_response.c (limited to 'sysdeps/unix/sysv') diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile index 2c67a6619f..d6cc529885 100644 --- a/sysdeps/unix/sysv/linux/Makefile +++ b/sysdeps/unix/sysv/linux/Makefile @@ -151,6 +151,7 @@ sysdep_headers += netinet/if_fddi.h netinet/if_tr.h \ netipx/ipx.h netash/ash.h netax25/ax25.h netatalk/at.h \ netrom/netrom.h netpacket/packet.h netrose/rose.h \ neteconet/ec.h netiucv/iucv.h +sysdep_routines += netlink_assert_response endif # Don't compile the ctype glue code, since there is no old non-GNU C library. diff --git a/sysdeps/unix/sysv/linux/Versions b/sysdeps/unix/sysv/linux/Versions index 16bb281590..202ffccc29 100644 --- a/sysdeps/unix/sysv/linux/Versions +++ b/sysdeps/unix/sysv/linux/Versions @@ -169,5 +169,7 @@ libc { GLIBC_PRIVATE { # functions used in other libraries __syscall_rt_sigqueueinfo; + # functions used by nscd + __netlink_assert_response; } } diff --git a/sysdeps/unix/sysv/linux/check_native.c b/sysdeps/unix/sysv/linux/check_native.c index eaefca10e4..d04c8f2a1f 100644 --- a/sysdeps/unix/sysv/linux/check_native.c +++ b/sysdeps/unix/sysv/linux/check_native.c @@ -35,6 +35,7 @@ #include +#include "netlinkaccess.h" void __check_native (uint32_t a1_index, int *a1_native, @@ -117,6 +118,7 @@ __check_native (uint32_t a1_index, int *a1_native, }; ssize_t read_len = TEMP_FAILURE_RETRY (__recvmsg (fd, &msg, 0)); + __netlink_assert_response (fd, read_len); if (read_len < 0) goto out_fail; diff --git a/sysdeps/unix/sysv/linux/check_pf.c b/sysdeps/unix/sysv/linux/check_pf.c index f072fb3de7..af4fdf8d9a 100644 --- a/sysdeps/unix/sysv/linux/check_pf.c +++ b/sysdeps/unix/sysv/linux/check_pf.c @@ -36,6 +36,7 @@ #include #include +#include "netlinkaccess.h" #ifndef IFA_F_HOMEADDRESS # define IFA_F_HOMEADDRESS 0 @@ -164,7 +165,8 @@ make_request (int fd, pid_t pid) }; ssize_t read_len = TEMP_FAILURE_RETRY (__recvmsg (fd, &msg, 0)); - if (read_len <= 0) + __netlink_assert_response (fd, read_len); + if (read_len < 0) goto out_fail; if (msg.msg_flags & MSG_TRUNC) diff --git a/sysdeps/unix/sysv/linux/ifaddrs.c b/sysdeps/unix/sysv/linux/ifaddrs.c index 64b4a1c859..768a7ed798 100644 --- a/sysdeps/unix/sysv/linux/ifaddrs.c +++ b/sysdeps/unix/sysv/linux/ifaddrs.c @@ -168,6 +168,7 @@ __netlink_request (struct netlink_handle *h, int type) }; read_len = TEMP_FAILURE_RETRY (__recvmsg (h->fd, &msg, 0)); + __netlink_assert_response (h->fd, read_len); if (read_len < 0) goto out_fail; diff --git a/sysdeps/unix/sysv/linux/netlink_assert_response.c b/sysdeps/unix/sysv/linux/netlink_assert_response.c new file mode 100644 index 0000000000..b570e93db8 --- /dev/null +++ b/sysdeps/unix/sysv/linux/netlink_assert_response.c @@ -0,0 +1,106 @@ +/* Check recvmsg results for netlink sockets. + Copyright (C) 2015 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + . */ + +#include +#include +#include +#include + +#include "netlinkaccess.h" + +static int +get_address_family (int fd) +{ + struct sockaddr_storage sa; + socklen_t sa_len = sizeof (sa); + if (__getsockname (fd, (struct sockaddr *) &sa, &sa_len) < 0) + return -1; + /* Check that the socket family number is preserved despite in-band + signaling. */ + _Static_assert (sizeof (sa.ss_family) < sizeof (int), "address family size"); + _Static_assert (0 < (__typeof__ (sa.ss_family)) -1, + "address family unsigned"); + return sa.ss_family; +} + +void +internal_function +__netlink_assert_response (int fd, ssize_t result) +{ + if (result < 0) + { + /* Check if the error is unexpected. */ + bool terminate = false; + int error_code = errno; + int family = get_address_family (fd); + if (family != AF_NETLINK) + /* If the address family does not match (or getsockname + failed), report the original error. */ + terminate = true; + else if (error_code == EBADF + || error_code == ENOTCONN + || error_code == ENOTSOCK + || error_code == ECONNREFUSED) + /* These errors indicate that the descriptor is not a + connected socket. */ + terminate = true; + else if (error_code == EAGAIN || error_code == EWOULDBLOCK) + { + /* The kernel might return EAGAIN for other reasons than a + non-blocking socket. But if the socket is not blocking, + it is not ours, so report the error. */ + int mode = __fcntl (fd, F_GETFL, 0); + if (mode < 0 || (mode & O_NONBLOCK) != 0) + terminate = true; + } + if (terminate) + { + char message[200]; + if (family < 0) + __snprintf (message, sizeof (message), + "Unexpected error %d on netlink descriptor %d", + error_code, fd); + else + __snprintf (message, sizeof (message), + "Unexpected error %d on netlink descriptor %d" + " (address family %d)", + error_code, fd, family); + __libc_fatal (message); + } + else + /* Restore orignal errno value. */ + __set_errno (error_code); + } + else if (result < sizeof (struct nlmsghdr)) + { + char message[200]; + int family = get_address_family (fd); + if (family < 0) + __snprintf (message, sizeof (message), + "Unexpected netlink response of size %zd" + " on descriptor %d", + result, fd); + else + __snprintf (message, sizeof (message), + "Unexpected netlink response of size %zd" + " on descriptor %d (address family %d)", + result, fd, family); + __libc_fatal (message); + } +} +libc_hidden_def (__netlink_assert_response) diff --git a/sysdeps/unix/sysv/linux/netlinkaccess.h b/sysdeps/unix/sysv/linux/netlinkaccess.h index c204b67a20..01ac35c641 100644 --- a/sysdeps/unix/sysv/linux/netlinkaccess.h +++ b/sysdeps/unix/sysv/linux/netlinkaccess.h @@ -19,6 +19,7 @@ #define _NETLINKACCESS_H 1 #include +#include #include #include #include @@ -48,5 +49,10 @@ extern void __netlink_close (struct netlink_handle *h); extern void __netlink_free_handle (struct netlink_handle *h); extern int __netlink_request (struct netlink_handle *h, int type); +/* Terminate the process if RESULT is an invalid recvmsg result for + the netlink socket FD. */ +void __netlink_assert_response (int fd, ssize_t result) + internal_function; +libc_hidden_proto (__netlink_assert_response) #endif /* netlinkaccess.h */ -- cgit 1.4.1