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![Vlad Yasevich](/assets/img/avatar_default.png)
Currently, it is possible to create an SCTP socket, then switch auth_enable via sysctl setting to 1 and crash the system on connect: Oops[#1]: CPU: 0 PID: 0 Comm: swapper Not tainted 3.14.1-mipsgit-20140415 #1 task: ffffffff8056ce80 ti: ffffffff8055c000 task.ti: ffffffff8055c000 [...] Call Trace: [<ffffffff8043c4e8>] sctp_auth_asoc_set_default_hmac+0x68/0x80 [<ffffffff8042b300>] sctp_process_init+0x5e0/0x8a4 [<ffffffff8042188c>] sctp_sf_do_5_1B_init+0x234/0x34c [<ffffffff804228c8>] sctp_do_sm+0xb4/0x1e8 [<ffffffff80425a08>] sctp_endpoint_bh_rcv+0x1c4/0x214 [<ffffffff8043af68>] sctp_rcv+0x588/0x630 [<ffffffff8043e8e8>] sctp6_rcv+0x10/0x24 [<ffffffff803acb50>] ip6_input+0x2c0/0x440 [<ffffffff8030fc00>] __netif_receive_skb_core+0x4a8/0x564 [<ffffffff80310650>] process_backlog+0xb4/0x18c [<ffffffff80313cbc>] net_rx_action+0x12c/0x210 [<ffffffff80034254>] __do_softirq+0x17c/0x2ac [<ffffffff800345e0>] irq_exit+0x54/0xb0 [<ffffffff800075a4>] ret_from_irq+0x0/0x4 [<ffffffff800090ec>] rm7k_wait_irqoff+0x24/0x48 [<ffffffff8005e388>] cpu_startup_entry+0xc0/0x148 [<ffffffff805a88b0>] start_kernel+0x37c/0x398 Code: dd0900b8 000330f8 0126302d <dcc60000> 50c0fff1 0047182a a48306a0 03e00008 00000000 ---[ end trace b530b0551467f2fd ]--- Kernel panic - not syncing: Fatal exception in interrupt What happens while auth_enable=0 in that case is, that ep->auth_hmacs is initialized to NULL in sctp_auth_init_hmacs() when endpoint is being created. After that point, if an admin switches over to auth_enable=1, the machine can crash due to NULL pointer dereference during reception of an INIT chunk. When we enter sctp_process_init() via sctp_sf_do_5_1B_init() in order to respond to an INIT chunk, the INIT verification succeeds and while we walk and process all INIT params via sctp_process_param() we find that net->sctp.auth_enable is set, therefore do not fall through, but invoke sctp_auth_asoc_set_default_hmac() instead, and thus, dereference what we have set to NULL during endpoint initialization phase. The fix is to make auth_enable immutable by caching its value during endpoint initialization, so that its original value is being carried along until destruction. The bug seems to originate from the very first days. Fix in joint work with Daniel Borkmann. Reported-by: Joshua Kinard <kumba@gentoo.org> Signed-off-by: Vlad Yasevich <vyasevic@redhat.com> Signed-off-by: Daniel Borkmann <dborkman@redhat.com> Acked-by: Neil Horman <nhorman@tuxdriver.com> Tested-by: Joshua Kinard <kumba@gentoo.org> Signed-off-by: David S. Miller <davem@davemloft.net>
477 lines
12 KiB
C
477 lines
12 KiB
C
/* SCTP kernel implementation
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* (C) Copyright IBM Corp. 2002, 2004
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* Copyright (c) 2002 Intel Corp.
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*
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* This file is part of the SCTP kernel implementation
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*
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* Sysctl related interfaces for SCTP.
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*
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* This SCTP implementation is free software;
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* you can redistribute it and/or modify it under the terms of
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* the GNU General Public License as published by
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* the Free Software Foundation; either version 2, or (at your option)
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* any later version.
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*
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* This SCTP implementation is distributed in the hope that it
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* will be useful, but WITHOUT ANY WARRANTY; without even the implied
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* ************************
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* warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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* See the GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with GNU CC; see the file COPYING. If not, see
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* <http://www.gnu.org/licenses/>.
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*
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* Please send any bug reports or fixes you make to the
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* email address(es):
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* lksctp developers <linux-sctp@vger.kernel.org>
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*
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* Written or modified by:
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* Mingqin Liu <liuming@us.ibm.com>
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* Jon Grimm <jgrimm@us.ibm.com>
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* Ardelle Fan <ardelle.fan@intel.com>
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* Ryan Layer <rmlayer@us.ibm.com>
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* Sridhar Samudrala <sri@us.ibm.com>
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*/
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#include <net/sctp/structs.h>
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#include <net/sctp/sctp.h>
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#include <linux/sysctl.h>
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static int zero = 0;
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static int one = 1;
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static int timer_max = 86400000; /* ms in one day */
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static int int_max = INT_MAX;
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static int sack_timer_min = 1;
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static int sack_timer_max = 500;
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static int addr_scope_max = 3; /* check sctp_scope_policy_t in include/net/sctp/constants.h for max entries */
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static int rwnd_scale_max = 16;
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static unsigned long max_autoclose_min = 0;
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static unsigned long max_autoclose_max =
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(MAX_SCHEDULE_TIMEOUT / HZ > UINT_MAX)
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? UINT_MAX : MAX_SCHEDULE_TIMEOUT / HZ;
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extern long sysctl_sctp_mem[3];
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extern int sysctl_sctp_rmem[3];
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extern int sysctl_sctp_wmem[3];
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static int proc_sctp_do_hmac_alg(struct ctl_table *ctl, int write,
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void __user *buffer, size_t *lenp,
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loff_t *ppos);
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static int proc_sctp_do_rto_min(struct ctl_table *ctl, int write,
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void __user *buffer, size_t *lenp,
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loff_t *ppos);
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static int proc_sctp_do_rto_max(struct ctl_table *ctl, int write,
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void __user *buffer, size_t *lenp,
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loff_t *ppos);
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static int proc_sctp_do_auth(struct ctl_table *ctl, int write,
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void __user *buffer, size_t *lenp,
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loff_t *ppos);
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static struct ctl_table sctp_table[] = {
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{
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.procname = "sctp_mem",
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.data = &sysctl_sctp_mem,
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.maxlen = sizeof(sysctl_sctp_mem),
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.mode = 0644,
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.proc_handler = proc_doulongvec_minmax
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},
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{
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.procname = "sctp_rmem",
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.data = &sysctl_sctp_rmem,
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.maxlen = sizeof(sysctl_sctp_rmem),
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.mode = 0644,
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.proc_handler = proc_dointvec,
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},
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{
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.procname = "sctp_wmem",
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.data = &sysctl_sctp_wmem,
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.maxlen = sizeof(sysctl_sctp_wmem),
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.mode = 0644,
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.proc_handler = proc_dointvec,
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},
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{ /* sentinel */ }
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};
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static struct ctl_table sctp_net_table[] = {
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{
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.procname = "rto_initial",
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.data = &init_net.sctp.rto_initial,
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.maxlen = sizeof(unsigned int),
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.mode = 0644,
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.proc_handler = proc_dointvec_minmax,
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.extra1 = &one,
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.extra2 = &timer_max
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},
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{
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.procname = "rto_min",
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.data = &init_net.sctp.rto_min,
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.maxlen = sizeof(unsigned int),
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.mode = 0644,
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.proc_handler = proc_sctp_do_rto_min,
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.extra1 = &one,
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.extra2 = &init_net.sctp.rto_max
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},
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{
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.procname = "rto_max",
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.data = &init_net.sctp.rto_max,
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.maxlen = sizeof(unsigned int),
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.mode = 0644,
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.proc_handler = proc_sctp_do_rto_max,
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.extra1 = &init_net.sctp.rto_min,
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.extra2 = &timer_max
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},
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{
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.procname = "rto_alpha_exp_divisor",
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.data = &init_net.sctp.rto_alpha,
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.maxlen = sizeof(int),
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.mode = 0444,
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.proc_handler = proc_dointvec,
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},
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{
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.procname = "rto_beta_exp_divisor",
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.data = &init_net.sctp.rto_beta,
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.maxlen = sizeof(int),
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.mode = 0444,
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.proc_handler = proc_dointvec,
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},
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{
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.procname = "max_burst",
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.data = &init_net.sctp.max_burst,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec_minmax,
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.extra1 = &zero,
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.extra2 = &int_max
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},
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{
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.procname = "cookie_preserve_enable",
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.data = &init_net.sctp.cookie_preserve_enable,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec,
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},
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{
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.procname = "cookie_hmac_alg",
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.data = &init_net.sctp.sctp_hmac_alg,
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.maxlen = 8,
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.mode = 0644,
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.proc_handler = proc_sctp_do_hmac_alg,
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},
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{
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.procname = "valid_cookie_life",
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.data = &init_net.sctp.valid_cookie_life,
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.maxlen = sizeof(unsigned int),
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.mode = 0644,
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.proc_handler = proc_dointvec_minmax,
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.extra1 = &one,
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.extra2 = &timer_max
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},
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{
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.procname = "sack_timeout",
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.data = &init_net.sctp.sack_timeout,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec_minmax,
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.extra1 = &sack_timer_min,
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.extra2 = &sack_timer_max,
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},
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{
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.procname = "hb_interval",
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.data = &init_net.sctp.hb_interval,
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.maxlen = sizeof(unsigned int),
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.mode = 0644,
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.proc_handler = proc_dointvec_minmax,
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.extra1 = &one,
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.extra2 = &timer_max
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},
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{
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.procname = "association_max_retrans",
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.data = &init_net.sctp.max_retrans_association,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec_minmax,
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.extra1 = &one,
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.extra2 = &int_max
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},
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{
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.procname = "path_max_retrans",
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.data = &init_net.sctp.max_retrans_path,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec_minmax,
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.extra1 = &one,
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.extra2 = &int_max
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},
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{
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.procname = "max_init_retransmits",
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.data = &init_net.sctp.max_retrans_init,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec_minmax,
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.extra1 = &one,
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.extra2 = &int_max
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},
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{
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.procname = "pf_retrans",
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.data = &init_net.sctp.pf_retrans,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec_minmax,
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.extra1 = &zero,
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.extra2 = &int_max
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},
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{
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.procname = "sndbuf_policy",
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.data = &init_net.sctp.sndbuf_policy,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec,
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},
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{
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.procname = "rcvbuf_policy",
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.data = &init_net.sctp.rcvbuf_policy,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec,
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},
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{
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.procname = "default_auto_asconf",
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.data = &init_net.sctp.default_auto_asconf,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec,
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},
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{
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.procname = "addip_enable",
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.data = &init_net.sctp.addip_enable,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec,
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},
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{
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.procname = "addip_noauth_enable",
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.data = &init_net.sctp.addip_noauth,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec,
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},
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{
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.procname = "prsctp_enable",
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.data = &init_net.sctp.prsctp_enable,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec,
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},
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{
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.procname = "auth_enable",
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.data = &init_net.sctp.auth_enable,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_sctp_do_auth,
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},
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{
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.procname = "addr_scope_policy",
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.data = &init_net.sctp.scope_policy,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec_minmax,
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.extra1 = &zero,
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.extra2 = &addr_scope_max,
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},
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{
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.procname = "rwnd_update_shift",
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.data = &init_net.sctp.rwnd_upd_shift,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = &proc_dointvec_minmax,
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.extra1 = &one,
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.extra2 = &rwnd_scale_max,
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},
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{
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.procname = "max_autoclose",
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.data = &init_net.sctp.max_autoclose,
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.maxlen = sizeof(unsigned long),
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.mode = 0644,
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.proc_handler = &proc_doulongvec_minmax,
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.extra1 = &max_autoclose_min,
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.extra2 = &max_autoclose_max,
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},
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{ /* sentinel */ }
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};
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static int proc_sctp_do_hmac_alg(struct ctl_table *ctl, int write,
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void __user *buffer, size_t *lenp,
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loff_t *ppos)
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{
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struct net *net = current->nsproxy->net_ns;
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char tmp[8];
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struct ctl_table tbl;
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int ret;
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int changed = 0;
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char *none = "none";
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memset(&tbl, 0, sizeof(struct ctl_table));
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if (write) {
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tbl.data = tmp;
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tbl.maxlen = 8;
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} else {
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tbl.data = net->sctp.sctp_hmac_alg ? : none;
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tbl.maxlen = strlen(tbl.data);
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}
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ret = proc_dostring(&tbl, write, buffer, lenp, ppos);
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if (write) {
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#ifdef CONFIG_CRYPTO_MD5
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if (!strncmp(tmp, "md5", 3)) {
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net->sctp.sctp_hmac_alg = "md5";
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changed = 1;
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}
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#endif
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#ifdef CONFIG_CRYPTO_SHA1
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if (!strncmp(tmp, "sha1", 4)) {
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net->sctp.sctp_hmac_alg = "sha1";
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changed = 1;
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}
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#endif
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if (!strncmp(tmp, "none", 4)) {
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net->sctp.sctp_hmac_alg = NULL;
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changed = 1;
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}
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if (!changed)
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ret = -EINVAL;
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}
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return ret;
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}
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static int proc_sctp_do_rto_min(struct ctl_table *ctl, int write,
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void __user *buffer, size_t *lenp,
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loff_t *ppos)
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{
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struct net *net = current->nsproxy->net_ns;
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int new_value;
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struct ctl_table tbl;
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unsigned int min = *(unsigned int *) ctl->extra1;
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unsigned int max = *(unsigned int *) ctl->extra2;
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int ret;
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memset(&tbl, 0, sizeof(struct ctl_table));
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tbl.maxlen = sizeof(unsigned int);
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if (write)
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tbl.data = &new_value;
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else
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tbl.data = &net->sctp.rto_min;
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ret = proc_dointvec(&tbl, write, buffer, lenp, ppos);
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if (write) {
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if (ret || new_value > max || new_value < min)
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return -EINVAL;
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net->sctp.rto_min = new_value;
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}
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return ret;
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}
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static int proc_sctp_do_rto_max(struct ctl_table *ctl, int write,
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void __user *buffer, size_t *lenp,
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loff_t *ppos)
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{
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struct net *net = current->nsproxy->net_ns;
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int new_value;
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struct ctl_table tbl;
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unsigned int min = *(unsigned int *) ctl->extra1;
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unsigned int max = *(unsigned int *) ctl->extra2;
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int ret;
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memset(&tbl, 0, sizeof(struct ctl_table));
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tbl.maxlen = sizeof(unsigned int);
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if (write)
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tbl.data = &new_value;
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else
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tbl.data = &net->sctp.rto_max;
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ret = proc_dointvec(&tbl, write, buffer, lenp, ppos);
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if (write) {
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if (ret || new_value > max || new_value < min)
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return -EINVAL;
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net->sctp.rto_max = new_value;
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}
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return ret;
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}
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static int proc_sctp_do_auth(struct ctl_table *ctl, int write,
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void __user *buffer, size_t *lenp,
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loff_t *ppos)
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{
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struct net *net = current->nsproxy->net_ns;
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struct ctl_table tbl;
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int new_value, ret;
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memset(&tbl, 0, sizeof(struct ctl_table));
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tbl.maxlen = sizeof(unsigned int);
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if (write)
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tbl.data = &new_value;
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else
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tbl.data = &net->sctp.auth_enable;
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ret = proc_dointvec(&tbl, write, buffer, lenp, ppos);
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if (write) {
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struct sock *sk = net->sctp.ctl_sock;
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net->sctp.auth_enable = new_value;
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/* Update the value in the control socket */
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lock_sock(sk);
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sctp_sk(sk)->ep->auth_enable = new_value;
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release_sock(sk);
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}
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return ret;
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}
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int sctp_sysctl_net_register(struct net *net)
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|
{
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|
struct ctl_table *table = sctp_net_table;
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|
|
|
if (!net_eq(net, &init_net)) {
|
|
int i;
|
|
|
|
table = kmemdup(sctp_net_table, sizeof(sctp_net_table), GFP_KERNEL);
|
|
if (!table)
|
|
return -ENOMEM;
|
|
|
|
for (i = 0; table[i].data; i++)
|
|
table[i].data += (char *)(&net->sctp) - (char *)&init_net.sctp;
|
|
}
|
|
|
|
net->sctp.sysctl_header = register_net_sysctl(net, "net/sctp", table);
|
|
return 0;
|
|
}
|
|
|
|
void sctp_sysctl_net_unregister(struct net *net)
|
|
{
|
|
struct ctl_table *table;
|
|
|
|
table = net->sctp.sysctl_header->ctl_table_arg;
|
|
unregister_net_sysctl_table(net->sctp.sysctl_header);
|
|
kfree(table);
|
|
}
|
|
|
|
static struct ctl_table_header *sctp_sysctl_header;
|
|
|
|
/* Sysctl registration. */
|
|
void sctp_sysctl_register(void)
|
|
{
|
|
sctp_sysctl_header = register_net_sysctl(&init_net, "net/sctp", sctp_table);
|
|
}
|
|
|
|
/* Sysctl deregistration. */
|
|
void sctp_sysctl_unregister(void)
|
|
{
|
|
unregister_net_sysctl_table(sctp_sysctl_header);
|
|
}
|