net-sctp: CVE-2015-1421

Fix slab corruption from use after free on INIT collisions

Reference:
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-1421

Upstream fix:
https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/patch/
?id=43e39c2f63240f67a67b4060882f67dac1a6f339

Signed-off-by: Sona Sarmadi <sona.sarmadi@enea.com>
Signed-off-by: Zhenhua Luo <zhenhua.luo@nxp.com>

2 files changed, 139 insertions, 0 deletions

diff --git a/recipes-kernel/linux/files/net-sctp-CVE-2015-1421.patch b/recipes-kernel/linux/files/net-sctp-CVE-2015-1421.patch
new file mode 100644
index 0000000..37e04f5
--- /dev/null
+++ b/recipes-kernel/linux/files/net-sctp-CVE-2015-1421.patch
@@ -0,0 +1,138 @@
+commit 43e39c2f63240f67a67b4060882f67dac1a6f339
+Author: Daniel Borkmann <dborkman@redhat.com>
+Date: Thu, 22 Jan 2015 18:26:54 +0100
+Subject: net: sctp: fix slab corruption from use after free on INIT collisions
+
+[ Upstream commit 600ddd6825543962fb807884169e57b580dba208 ]
+
+When hitting an INIT collision case during the 4WHS with AUTH enabled, as
+already described in detail in commit 1be9a950c646 ("net: sctp: inherit
+auth_capable on INIT collisions"), it can happen that we occasionally
+still remotely trigger the following panic on server side which seems to
+have been uncovered after the fix from commit 1be9a950c646 ...
+
+[  533.876389] BUG: unable to handle kernel paging request at 00000000ffffffff
+[  533.913657] IP: [<ffffffff811ac385>] __kmalloc+0x95/0x230
+[  533.940559] PGD 5030f2067 PUD 0
+[  533.957104] Oops: 0000 [#1] SMP
+[  533.974283] Modules linked in: sctp mlx4_en [...]
+[  534.939704] Call Trace:
+[  534.951833]  [<ffffffff81294e30>] ? crypto_init_shash_ops+0x60/0xf0
+[  534.984213]  [<ffffffff81294e30>] crypto_init_shash_ops+0x60/0xf0
+[  535.015025]  [<ffffffff8128c8ed>] __crypto_alloc_tfm+0x6d/0x170
+[  535.045661]  [<ffffffff8128d12c>] crypto_alloc_base+0x4c/0xb0
+[  535.074593]  [<ffffffff8160bd42>] ? _raw_spin_lock_bh+0x12/0x50
+[  535.105239]  [<ffffffffa0418c11>] sctp_inet_listen+0x161/0x1e0 [sctp]
+[  535.138606]  [<ffffffff814e43bd>] SyS_listen+0x9d/0xb0
+[  535.166848]  [<ffffffff816149a9>] system_call_fastpath+0x16/0x1b
+
+... or depending on the the application, for example this one:
+
+[ 1370.026490] BUG: unable to handle kernel paging request at 00000000ffffffff
+[ 1370.026506] IP: [<ffffffff811ab455>] kmem_cache_alloc+0x75/0x1d0
+[ 1370.054568] PGD 633c94067 PUD 0
+[ 1370.070446] Oops: 0000 [#1] SMP
+[ 1370.085010] Modules linked in: sctp kvm_amd kvm [...]
+[ 1370.963431] Call Trace:
+[ 1370.974632]  [<ffffffff8120f7cf>] ? SyS_epoll_ctl+0x53f/0x960
+[ 1371.000863]  [<ffffffff8120f7cf>] SyS_epoll_ctl+0x53f/0x960
+[ 1371.027154]  [<ffffffff812100d3>] ? anon_inode_getfile+0xd3/0x170
+[ 1371.054679]  [<ffffffff811e3d67>] ? __alloc_fd+0xa7/0x130
+[ 1371.080183]  [<ffffffff816149a9>] system_call_fastpath+0x16/0x1b
+
+With slab debugging enabled, we can see that the poison has been overwritten:
+
+[  669.826368] BUG kmalloc-128 (Tainted: G        W     ): Poison overwritten
+[  669.826385] INFO: 0xffff880228b32e50-0xffff880228b32e50. First byte 0x6a instead of 0x6b
+[  669.826414] INFO: Allocated in sctp_auth_create_key+0x23/0x50 [sctp] age=3 cpu=0 pid=18494
+[  669.826424]  __slab_alloc+0x4bf/0x566
+[  669.826433]  __kmalloc+0x280/0x310
+[  669.826453]  sctp_auth_create_key+0x23/0x50 [sctp]
+[  669.826471]  sctp_auth_asoc_create_secret+0xcb/0x1e0 [sctp]
+[  669.826488]  sctp_auth_asoc_init_active_key+0x68/0xa0 [sctp]
+[  669.826505]  sctp_do_sm+0x29d/0x17c0 [sctp] [...]
+[  669.826629] INFO: Freed in kzfree+0x31/0x40 age=1 cpu=0 pid=18494
+[  669.826635]  __slab_free+0x39/0x2a8
+[  669.826643]  kfree+0x1d6/0x230
+[  669.826650]  kzfree+0x31/0x40
+[  669.826666]  sctp_auth_key_put+0x19/0x20 [sctp]
+[  669.826681]  sctp_assoc_update+0x1ee/0x2d0 [sctp]
+[  669.826695]  sctp_do_sm+0x674/0x17c0 [sctp]
+
+Since this only triggers in some collision-cases with AUTH, the problem at
+heart is that sctp_auth_key_put() on asoc->asoc_shared_key is called twice
+when having refcnt 1, once directly in sctp_assoc_update() and yet again
+from within sctp_auth_asoc_init_active_key() via sctp_assoc_update() on
+the already kzfree'd memory, which is also consistent with the observation
+of the poison decrease from 0x6b to 0x6a (note: the overwrite is detected
+at a later point in time when poison is checked on new allocation).
+
+Reference counting of auth keys revisited:
+
+Shared keys for AUTH chunks are being stored in endpoints and associations
+in endpoint_shared_keys list. On endpoint creation, a null key is being
+added; on association creation, all endpoint shared keys are being cached
+and thus cloned over to the association. struct sctp_shared_key only holds
+a pointer to the actual key bytes, that is, struct sctp_auth_bytes which
+keeps track of users internally through refcounting. Naturally, on assoc
+or enpoint destruction, sctp_shared_key are being destroyed directly and
+the reference on sctp_auth_bytes dropped.
+
+User space can add keys to either list via setsockopt(2) through struct
+sctp_authkey and by passing that to sctp_auth_set_key() which replaces or
+adds a new auth key. There, sctp_auth_create_key() creates a new sctp_auth_bytes
+with refcount 1 and in case of replacement drops the reference on the old
+sctp_auth_bytes. A key can be set active from user space through setsockopt()
+on the id via sctp_auth_set_active_key(), which iterates through either
+endpoint_shared_keys and in case of an assoc, invokes (one of various places)
+sctp_auth_asoc_init_active_key().
+
+sctp_auth_asoc_init_active_key() computes the actual secret from local's
+and peer's random, hmac and shared key parameters and returns a new key
+directly as sctp_auth_bytes, that is asoc->asoc_shared_key, plus drops
+the reference if there was a previous one. The secret, which where we
+eventually double drop the ref comes from sctp_auth_asoc_set_secret() with
+intitial refcount of 1, which also stays unchanged eventually in
+sctp_assoc_update(). This key is later being used for crypto layer to
+set the key for the hash in crypto_hash_setkey() from sctp_auth_calculate_hmac().
+
+To close the loop: asoc->asoc_shared_key is freshly allocated secret
+material and independant of the sctp_shared_key management keeping track
+of only shared keys in endpoints and assocs. Hence, also commit 4184b2a79a76
+("net: sctp: fix memory leak in auth key management") is independant of
+this bug here since it concerns a different layer (though same structures
+being used eventually). asoc->asoc_shared_key is reference dropped correctly
+on assoc destruction in sctp_association_free() and when active keys are
+being replaced in sctp_auth_asoc_init_active_key(), it always has a refcount
+of 1. Hence, it's freed prematurely in sctp_assoc_update(). Simple fix is
+to remove that sctp_auth_key_put() from there which fixes these panics.
+
+Fixes CVE-2015-1421
+Upstream-Status: Backport
+
+Fixes: 730fc3d05cd4 ("[SCTP]: Implete SCTP-AUTH parameter processing")
+Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
+Acked-by: Vlad Yasevich <vyasevich@gmail.com>
+Acked-by: Neil Horman <nhorman@tuxdriver.com>
+Signed-off-by: David S. Miller <davem@davemloft.net>
+Signed-off-by: Jiri Slaby <jslaby@suse.cz>
+Signed-off-by: Sona Sarmadi <sona.sarmadi@enea.com>
+---
+ net/sctp/associola.c | 1 -
+ 1 file changed, 1 deletion(-)
+
+diff --git a/net/sctp/associola.c b/net/sctp/associola.c
+index 737050f..88ca530 100644
+--- a/net/sctp/associola.c
++++ b/net/sctp/associola.c
+@@ -1282,7 +1282,6 @@ void sctp_assoc_update(struct sctp_association *asoc,
+        asoc->peer.peer_hmacs = new->peer.peer_hmacs;
+        new->peer.peer_hmacs = NULL;
+ 
+-       sctp_auth_key_put(asoc->asoc_shared_key);
+        sctp_auth_asoc_init_active_key(asoc, GFP_ATOMIC);
+ }
+ 
+-- 
+cgit v0.11.2
+
diff --git a/recipes-kernel/linux/linux-qoriq_3.12.bb b/recipes-kernel/linux/linux-qoriq_3.12.bb
index e89a289..8587b48 100644
--- a/recipes-kernel/linux/linux-qoriq_3.12.bb
+++ b/recipes-kernel/linux/linux-qoriq_3.12.bb
@@ -35,6 +35,7 @@ SRC_URI = "git://git.freescale.com/ppc/sdk/linux.git;nobranch=1 \
     file://udp-CVE-2015-5364_CVE-2015-5366.patch \
     file://mm-CVE-2014-3122.patch \
     file://media-ttusb-dec-CVE-2014-8884.patch \
+    file://net-sctp-CVE-2015-1421.patch \
 "
 SRCREV = "6619b8b55796cdf0cec04b66a71288edd3057229"