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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	stable@vger.kernel.org, Jann Horn <jannh@google.com>,
	"David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.14 15/80] tcp: dont read out-of-bounds opsize
Date: Fri, 27 Apr 2018 15:58:08 +0200	[thread overview]
Message-ID: <20180427135733.696691048@linuxfoundation.org> (raw)
In-Reply-To: <20180427135732.928644313@linuxfoundation.org>

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jann Horn <jannh@google.com>


[ Upstream commit 7e5a206ab686f098367b61aca989f5cdfa8114a3 ]

The old code reads the "opsize" variable from out-of-bounds memory (first
byte behind the segment) if a broken TCP segment ends directly after an
opcode that is neither EOL nor NOP.

The result of the read isn't used for anything, so the worst thing that
could theoretically happen is a pagefault; and since the physmap is usually
mostly contiguous, even that seems pretty unlikely.

The following C reproducer triggers the uninitialized read - however, you
can't actually see anything happen unless you put something like a
pr_warn() in tcp_parse_md5sig_option() to print the opsize.

====================================
#define _GNU_SOURCE
#include <arpa/inet.h>
#include <stdlib.h>
#include <errno.h>
#include <stdarg.h>
#include <net/if.h>
#include <linux/if.h>
#include <linux/ip.h>
#include <linux/tcp.h>
#include <linux/in.h>
#include <linux/if_tun.h>
#include <err.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <assert.h>

void systemf(const char *command, ...) {
  char *full_command;
  va_list ap;
  va_start(ap, command);
  if (vasprintf(&full_command, command, ap) == -1)
    err(1, "vasprintf");
  va_end(ap);
  printf("systemf: <<<%s>>>\n", full_command);
  system(full_command);
}

char *devname;

int tun_alloc(char *name) {
  int fd = open("/dev/net/tun", O_RDWR);
  if (fd == -1)
    err(1, "open tun dev");
  static struct ifreq req = { .ifr_flags = IFF_TUN|IFF_NO_PI };
  strcpy(req.ifr_name, name);
  if (ioctl(fd, TUNSETIFF, &req))
    err(1, "TUNSETIFF");
  devname = req.ifr_name;
  printf("device name: %s\n", devname);
  return fd;
}

#define IPADDR(a,b,c,d) (((a)<<0)+((b)<<8)+((c)<<16)+((d)<<24))

void sum_accumulate(unsigned int *sum, void *data, int len) {
  assert((len&2)==0);
  for (int i=0; i<len/2; i++) {
    *sum += ntohs(((unsigned short *)data)[i]);
  }
}

unsigned short sum_final(unsigned int sum) {
  sum = (sum >> 16) + (sum & 0xffff);
  sum = (sum >> 16) + (sum & 0xffff);
  return htons(~sum);
}

void fix_ip_sum(struct iphdr *ip) {
  unsigned int sum = 0;
  sum_accumulate(&sum, ip, sizeof(*ip));
  ip->check = sum_final(sum);
}

void fix_tcp_sum(struct iphdr *ip, struct tcphdr *tcp) {
  unsigned int sum = 0;
  struct {
    unsigned int saddr;
    unsigned int daddr;
    unsigned char pad;
    unsigned char proto_num;
    unsigned short tcp_len;
  } fakehdr = {
    .saddr = ip->saddr,
    .daddr = ip->daddr,
    .proto_num = ip->protocol,
    .tcp_len = htons(ntohs(ip->tot_len) - ip->ihl*4)
  };
  sum_accumulate(&sum, &fakehdr, sizeof(fakehdr));
  sum_accumulate(&sum, tcp, tcp->doff*4);
  tcp->check = sum_final(sum);
}

int main(void) {
  int tun_fd = tun_alloc("inject_dev%d");
  systemf("ip link set %s up", devname);
  systemf("ip addr add 192.168.42.1/24 dev %s", devname);

  struct {
    struct iphdr ip;
    struct tcphdr tcp;
    unsigned char tcp_opts[20];
  } __attribute__((packed)) syn_packet = {
    .ip = {
      .ihl = sizeof(struct iphdr)/4,
      .version = 4,
      .tot_len = htons(sizeof(syn_packet)),
      .ttl = 30,
      .protocol = IPPROTO_TCP,
      /* FIXUP check */
      .saddr = IPADDR(192,168,42,2),
      .daddr = IPADDR(192,168,42,1)
    },
    .tcp = {
      .source = htons(1),
      .dest = htons(1337),
      .seq = 0x12345678,
      .doff = (sizeof(syn_packet.tcp)+sizeof(syn_packet.tcp_opts))/4,
      .syn = 1,
      .window = htons(64),
      .check = 0 /*FIXUP*/
    },
    .tcp_opts = {
      /* INVALID: trailing MD5SIG opcode after NOPs */
      1, 1, 1, 1, 1,
      1, 1, 1, 1, 1,
      1, 1, 1, 1, 1,
      1, 1, 1, 1, 19
    }
  };
  fix_ip_sum(&syn_packet.ip);
  fix_tcp_sum(&syn_packet.ip, &syn_packet.tcp);
  while (1) {
    int write_res = write(tun_fd, &syn_packet, sizeof(syn_packet));
    if (write_res != sizeof(syn_packet))
      err(1, "packet write failed");
  }
}
====================================

Fixes: cfb6eeb4c860 ("[TCP]: MD5 Signature Option (RFC2385) support.")
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/ipv4/tcp_input.c |    7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3892,11 +3892,8 @@ const u8 *tcp_parse_md5sig_option(const
 	int length = (th->doff << 2) - sizeof(*th);
 	const u8 *ptr = (const u8 *)(th + 1);
 
-	/* If the TCP option is too short, we can short cut */
-	if (length < TCPOLEN_MD5SIG)
-		return NULL;
-
-	while (length > 0) {
+	/* If not enough data remaining, we can short cut */
+	while (length >= TCPOLEN_MD5SIG) {
 		int opcode = *ptr++;
 		int opsize;
 

  parent reply	other threads:[~2018-04-27 13:58 UTC|newest]

Thread overview: 90+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-27 13:57 [PATCH 4.14 00/80] 4.14.38-stable review Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 4.14 01/80] Revert "pinctrl: intel: Initialize GPIO properly when used through irqchip" Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 4.14 02/80] drm: bridge: dw-hdmi: Fix overflow workaround for Amlogic Meson GX SoCs Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 4.14 03/80] i40e: Fix attach VF to VM issue Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 4.14 04/80] tpm: cmd_ready command can be issued only after granting locality Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 4.14 05/80] tpm: tpm-interface: fix tpm_transmit/_cmd kdoc Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 4.14 06/80] tpm: add retry logic Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 07/80] Revert "ath10k: send (re)assoc peer command when NSS changed" Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 08/80] bonding: do not set slave_dev npinfo before slave_enable_netpoll in bond_enslave Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 09/80] ipv6: add RTA_TABLE and RTA_PREFSRC to rtm_ipv6_policy Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 10/80] ipv6: sr: fix NULL pointer dereference in seg6_do_srh_encap()- v4 pkts Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 11/80] KEYS: DNS: limit the length of option strings Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 12/80] l2tp: check sockaddr length in pppol2tp_connect() Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 13/80] net: validate attribute sizes in neigh_dump_table() Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 14/80] llc: delete timers synchronously in llc_sk_free() Greg Kroah-Hartman
2018-04-27 13:58 ` Greg Kroah-Hartman [this message]
2018-04-27 13:58 ` [PATCH 4.14 16/80] net: af_packet: fix race in PACKET_{R|T}X_RING Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 17/80] tcp: md5: reject TCP_MD5SIG or TCP_MD5SIG_EXT on established sockets Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 18/80] net: fix deadlock while clearing neighbor proxy table Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 19/80] team: avoid adding twice the same option to the event list Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 20/80] net/smc: fix shutdown in state SMC_LISTEN Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 21/80] team: fix netconsole setup over team Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 22/80] packet: fix bitfield update race Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 23/80] tipc: add policy for TIPC_NLA_NET_ADDR Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 24/80] pppoe: check sockaddr length in pppoe_connect() Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 25/80] vlan: Fix reading memory beyond skb->tail in skb_vlan_tagged_multi Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 26/80] amd-xgbe: Add pre/post auto-negotiation phy hooks Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 27/80] sctp: do not check port in sctp_inet6_cmp_addr Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 28/80] amd-xgbe: Improve KR auto-negotiation and training Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 29/80] strparser: Do not call mod_delayed_work with a timeout of LONG_MAX Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 30/80] amd-xgbe: Only use the SFP supported transceiver signals Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 31/80] strparser: Fix incorrect strp->need_bytes value Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 32/80] net: sched: ife: signal not finding metaid Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 33/80] tcp: clear tp->packets_out when purging write queue Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 34/80] net: sched: ife: handle malformed tlv length Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 35/80] net: sched: ife: check on metadata length Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 36/80] llc: hold llc_sap before release_sock() Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 37/80] llc: fix NULL pointer deref for SOCK_ZAPPED Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 38/80] net: ethernet: ti: cpsw: fix tx vlan priority mapping Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 39/80] virtio_net: split out ctrl buffer Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 40/80] virtio_net: fix adding vids on big-endian Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 41/80] Revert "microblaze: fix endian handling" Greg Kroah-Hartman
2018-04-27 15:43   ` Guenter Roeck
2018-04-27 16:25   ` Guenter Roeck
2018-04-28  5:50     ` Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 42/80] s390: introduce CPU alternatives Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 43/80] s390: enable CPU alternatives unconditionally Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 44/80] KVM: s390: wire up bpb feature Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 45/80] s390: scrub registers on kernel entry and KVM exit Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 46/80] s390: add optimized array_index_mask_nospec Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 47/80] s390/alternative: use a copy of the facility bit mask Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 48/80] s390: add options to change branch prediction behaviour for the kernel Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 49/80] s390: run user space and KVM guests with modified branch prediction Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 50/80] s390: introduce execute-trampolines for branches Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 51/80] KVM: s390: force bp isolation for VSIE Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 52/80] s390: Replace IS_ENABLED(EXPOLINE_*) with IS_ENABLED(CONFIG_EXPOLINE_*) Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 53/80] s390: do not bypass BPENTER for interrupt system calls Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 54/80] s390/entry.S: fix spurious zeroing of r0 Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 55/80] s390: move nobp parameter functions to nospec-branch.c Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 56/80] s390: add automatic detection of the spectre defense Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 57/80] s390: report spectre mitigation via syslog Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 58/80] s390: add sysfs attributes for spectre Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 59/80] s390: correct nospec auto detection init order Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 60/80] s390: correct module section names for expoline code revert Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 61/80] microblaze: Setup dependencies for ASM optimized lib functions Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 62/80] arm64: dts: rockchip: remove vdd_log from rk3399-puma Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 63/80] Revert "mm/hmm: fix header file if/else/endif maze" Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 64/80] commoncap: Handle memory allocation failure Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 65/80] scsi: mptsas: Disable WRITE SAME Greg Kroah-Hartman
2018-04-27 13:58 ` [PATCH 4.14 66/80] cdrom: information leak in cdrom_ioctl_media_changed() Greg Kroah-Hartman
2018-04-27 13:59 ` [PATCH 4.14 67/80] fsnotify: Fix fsnotify_mark_connector race Greg Kroah-Hartman
2018-04-27 13:59 ` [PATCH 4.14 68/80] m68k/mac: Dont remap SWIM MMIO region Greg Kroah-Hartman
2018-04-27 13:59 ` [PATCH 4.14 69/80] block/swim: Check drive type Greg Kroah-Hartman
2018-04-27 13:59 ` [PATCH 4.14 70/80] block/swim: Dont log an error message for an invalid ioctl Greg Kroah-Hartman
2018-04-27 13:59 ` [PATCH 4.14 71/80] block/swim: Remove extra put_disk() call from error path Greg Kroah-Hartman
2018-04-27 13:59 ` [PATCH 4.14 72/80] block/swim: Rename macros to avoid inconsistent inverted logic Greg Kroah-Hartman
2018-04-27 13:59 ` [PATCH 4.14 73/80] block/swim: Select appropriate drive on device open Greg Kroah-Hartman
2018-04-27 13:59 ` [PATCH 4.14 74/80] block/swim: Fix array bounds check Greg Kroah-Hartman
2018-04-27 13:59 ` [PATCH 4.14 75/80] block/swim: Fix IO error at end of medium Greg Kroah-Hartman
2018-04-27 13:59 ` [PATCH 4.14 76/80] tracing: Fix missing tab for hwlat_detector print format Greg Kroah-Hartman
2018-04-27 13:59 ` [PATCH 4.14 77/80] s390/cio: update chpid descriptor after resource accessibility event Greg Kroah-Hartman
2018-04-27 13:59 ` [PATCH 4.14 78/80] s390/dasd: fix IO error for newly defined devices Greg Kroah-Hartman
2018-04-27 13:59 ` [PATCH 4.14 79/80] s390/uprobes: implement arch_uretprobe_is_alive() Greg Kroah-Hartman
2018-04-27 13:59 ` [PATCH 4.14 80/80] ACPI / video: Only default only_lcd to true on Win8-ready _desktops_ Greg Kroah-Hartman
2018-04-27 18:14 ` [PATCH 4.14 00/80] 4.14.38-stable review Shuah Khan
2018-04-27 19:24 ` kernelci.org bot
2018-04-27 19:33 ` Nathan Chancellor
2018-04-28  5:06   ` Greg Kroah-Hartman
2018-04-27 20:37 ` Dan Rue
2018-04-28 14:28 ` Guenter Roeck

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