[linux] 02/02: sctp: fix race on protocol/netns initialization (CVE-2015-5283)
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Fri Oct 2 03:09:27 UTC 2015
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benh pushed a commit to branch jessie-security
in repository linux.
commit d7125c8d9d012239b43baaeabb13d332f476182b
Author: Ben Hutchings <ben at decadent.org.uk>
Date: Fri Oct 2 02:43:26 2015 +0100
sctp: fix race on protocol/netns initialization (CVE-2015-5283)
---
debian/changelog | 1 +
...fix-race-on-protocol-netns-initialization.patch | 227 +++++++++++++++++++++
debian/patches/series | 1 +
3 files changed, 229 insertions(+)
diff --git a/debian/changelog b/debian/changelog
index 8b0fb39..83d60e7 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,6 +1,7 @@
linux (3.16.7-ckt11-1+deb8u5) UNRELEASED; urgency=medium
* USB: whiteheat: fix potential null-deref at probe (CVE-2015-5257)
+ * sctp: fix race on protocol/netns initialization (CVE-2015-5283)
-- Ben Hutchings <ben at decadent.org.uk> Fri, 02 Oct 2015 02:39:36 +0100
diff --git a/debian/patches/bugfix/all/sctp-fix-race-on-protocol-netns-initialization.patch b/debian/patches/bugfix/all/sctp-fix-race-on-protocol-netns-initialization.patch
new file mode 100644
index 0000000..b128cd4
--- /dev/null
+++ b/debian/patches/bugfix/all/sctp-fix-race-on-protocol-netns-initialization.patch
@@ -0,0 +1,227 @@
+From: Marcelo Ricardo Leitner <marcelo.leitner at gmail.com>
+Date: Thu, 10 Sep 2015 17:31:15 -0300
+Subject: sctp: fix race on protocol/netns initialization
+Origin: https://git.kernel.org/linus/8e2d61e0aed2b7c4ecb35844fe07e0b2b762dee4
+
+Consider sctp module is unloaded and is being requested because an user
+is creating a sctp socket.
+
+During initialization, sctp will add the new protocol type and then
+initialize pernet subsys:
+
+ status = sctp_v4_protosw_init();
+ if (status)
+ goto err_protosw_init;
+
+ status = sctp_v6_protosw_init();
+ if (status)
+ goto err_v6_protosw_init;
+
+ status = register_pernet_subsys(&sctp_net_ops);
+
+The problem is that after those calls to sctp_v{4,6}_protosw_init(), it
+is possible for userspace to create SCTP sockets like if the module is
+already fully loaded. If that happens, one of the possible effects is
+that we will have readers for net->sctp.local_addr_list list earlier
+than expected and sctp_net_init() does not take precautions while
+dealing with that list, leading to a potential panic but not limited to
+that, as sctp_sock_init() will copy a bunch of blank/partially
+initialized values from net->sctp.
+
+The race happens like this:
+
+ CPU 0 | CPU 1
+ socket() |
+ __sock_create | socket()
+ inet_create | __sock_create
+ list_for_each_entry_rcu( |
+ answer, &inetsw[sock->type], |
+ list) { | inet_create
+ /* no hits */ |
+ if (unlikely(err)) { |
+ ... |
+ request_module() |
+ /* socket creation is blocked |
+ * the module is fully loaded |
+ */ |
+ sctp_init |
+ sctp_v4_protosw_init |
+ inet_register_protosw |
+ list_add_rcu(&p->list, |
+ last_perm); |
+ | list_for_each_entry_rcu(
+ | answer, &inetsw[sock->type],
+ sctp_v6_protosw_init | list) {
+ | /* hit, so assumes protocol
+ | * is already loaded
+ | */
+ | /* socket creation continues
+ | * before netns is initialized
+ | */
+ register_pernet_subsys |
+
+Simply inverting the initialization order between
+register_pernet_subsys() and sctp_v4_protosw_init() is not possible
+because register_pernet_subsys() will create a control sctp socket, so
+the protocol must be already visible by then. Deferring the socket
+creation to a work-queue is not good specially because we loose the
+ability to handle its errors.
+
+So, as suggested by Vlad, the fix is to split netns initialization in
+two moments: defaults and control socket, so that the defaults are
+already loaded by when we register the protocol, while control socket
+initialization is kept at the same moment it is today.
+
+Fixes: 4db67e808640 ("sctp: Make the address lists per network namespace")
+Signed-off-by: Vlad Yasevich <vyasevich at gmail.com>
+Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner at gmail.com>
+Signed-off-by: David S. Miller <davem at davemloft.net>
+---
+ net/sctp/protocol.c | 64 ++++++++++++++++++++++++++++++++++-------------------
+ 1 file changed, 41 insertions(+), 23 deletions(-)
+
+--- a/net/sctp/protocol.c
++++ b/net/sctp/protocol.c
+@@ -1166,7 +1166,7 @@ static void sctp_v4_del_protocol(void)
+ unregister_inetaddr_notifier(&sctp_inetaddr_notifier);
+ }
+
+-static int __net_init sctp_net_init(struct net *net)
++static int __net_init sctp_defaults_init(struct net *net)
+ {
+ int status;
+
+@@ -1259,12 +1259,6 @@ static int __net_init sctp_net_init(stru
+
+ sctp_dbg_objcnt_init(net);
+
+- /* Initialize the control inode/socket for handling OOTB packets. */
+- if ((status = sctp_ctl_sock_init(net))) {
+- pr_err("Failed to initialize the SCTP control sock\n");
+- goto err_ctl_sock_init;
+- }
+-
+ /* Initialize the local address list. */
+ INIT_LIST_HEAD(&net->sctp.local_addr_list);
+ spin_lock_init(&net->sctp.local_addr_lock);
+@@ -1280,9 +1274,6 @@ static int __net_init sctp_net_init(stru
+
+ return 0;
+
+-err_ctl_sock_init:
+- sctp_dbg_objcnt_exit(net);
+- sctp_proc_exit(net);
+ err_init_proc:
+ cleanup_sctp_mibs(net);
+ err_init_mibs:
+@@ -1291,15 +1282,12 @@ err_sysctl_register:
+ return status;
+ }
+
+-static void __net_exit sctp_net_exit(struct net *net)
++static void __net_exit sctp_defaults_exit(struct net *net)
+ {
+ /* Free the local address list */
+ sctp_free_addr_wq(net);
+ sctp_free_local_addr_list(net);
+
+- /* Free the control endpoint. */
+- inet_ctl_sock_destroy(net->sctp.ctl_sock);
+-
+ sctp_dbg_objcnt_exit(net);
+
+ sctp_proc_exit(net);
+@@ -1307,9 +1295,32 @@ static void __net_exit sctp_net_exit(str
+ sctp_sysctl_net_unregister(net);
+ }
+
+-static struct pernet_operations sctp_net_ops = {
+- .init = sctp_net_init,
+- .exit = sctp_net_exit,
++static struct pernet_operations sctp_defaults_ops = {
++ .init = sctp_defaults_init,
++ .exit = sctp_defaults_exit,
++};
++
++static int __net_init sctp_ctrlsock_init(struct net *net)
++{
++ int status;
++
++ /* Initialize the control inode/socket for handling OOTB packets. */
++ status = sctp_ctl_sock_init(net);
++ if (status)
++ pr_err("Failed to initialize the SCTP control sock\n");
++
++ return status;
++}
++
++static void __net_init sctp_ctrlsock_exit(struct net *net)
++{
++ /* Free the control endpoint. */
++ inet_ctl_sock_destroy(net->sctp.ctl_sock);
++}
++
++static struct pernet_operations sctp_ctrlsock_ops = {
++ .init = sctp_ctrlsock_init,
++ .exit = sctp_ctrlsock_exit,
+ };
+
+ /* Initialize the universe into something sensible. */
+@@ -1443,8 +1454,11 @@ static __init int sctp_init(void)
+ sctp_v4_pf_init();
+ sctp_v6_pf_init();
+
+- status = sctp_v4_protosw_init();
++ status = register_pernet_subsys(&sctp_defaults_ops);
++ if (status)
++ goto err_register_defaults;
+
++ status = sctp_v4_protosw_init();
+ if (status)
+ goto err_protosw_init;
+
+@@ -1452,9 +1466,9 @@ static __init int sctp_init(void)
+ if (status)
+ goto err_v6_protosw_init;
+
+- status = register_pernet_subsys(&sctp_net_ops);
++ status = register_pernet_subsys(&sctp_ctrlsock_ops);
+ if (status)
+- goto err_register_pernet_subsys;
++ goto err_register_ctrlsock;
+
+ status = sctp_v4_add_protocol();
+ if (status)
+@@ -1470,12 +1484,14 @@ out:
+ err_v6_add_protocol:
+ sctp_v4_del_protocol();
+ err_add_protocol:
+- unregister_pernet_subsys(&sctp_net_ops);
+-err_register_pernet_subsys:
++ unregister_pernet_subsys(&sctp_ctrlsock_ops);
++err_register_ctrlsock:
+ sctp_v6_protosw_exit();
+ err_v6_protosw_init:
+ sctp_v4_protosw_exit();
+ err_protosw_init:
++ unregister_pernet_subsys(&sctp_defaults_ops);
++err_register_defaults:
+ sctp_v4_pf_exit();
+ sctp_v6_pf_exit();
+ sctp_sysctl_unregister();
+@@ -1508,12 +1524,14 @@ static __exit void sctp_exit(void)
+ sctp_v6_del_protocol();
+ sctp_v4_del_protocol();
+
+- unregister_pernet_subsys(&sctp_net_ops);
++ unregister_pernet_subsys(&sctp_ctrlsock_ops);
+
+ /* Free protosw registrations */
+ sctp_v6_protosw_exit();
+ sctp_v4_protosw_exit();
+
++ unregister_pernet_subsys(&sctp_defaults_ops);
++
+ /* Unregister with socket layer. */
+ sctp_v6_pf_exit();
+ sctp_v4_pf_exit();
diff --git a/debian/patches/series b/debian/patches/series
index 64972a0..4201a5e 100644
--- a/debian/patches/series
+++ b/debian/patches/series
@@ -649,3 +649,4 @@ bugfix/all/namei-lift-open-coded-terminate_walk-in-follow_dotdo.patch
bugfix/all/dcache-handle-escaped-paths-in-prepend_path.patch
bugfix/all/vfs-test-for-and-handle-paths-that-are-unreachable-f.patch
bugfix/all/usb-whiteheat-fix-potential-null-deref-at-probe.patch
+bugfix/all/sctp-fix-race-on-protocol-netns-initialization.patch
--
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