[3.8.y.z extended stable] Patch "crypto: ccm - Fix handling of zero plaintext when computing mac" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    crypto: ccm - Fix handling of zero plaintext when computing mac

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.15.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From cc1cebf8678e6014b12719152fb16f2182822ced Mon Sep 17 00:00:00 2001
From: Horia Geanta <horia.geanta at freescale.com>
Date: Thu, 28 Nov 2013 15:11:15 +0200
Subject: crypto: ccm - Fix handling of zero plaintext when computing mac

commit 5638cabf3e4883f38dfb246c30980cebf694fbda upstream.

There are cases when cryptlen can be zero in crypto_ccm_auth():
-encryptiom: input scatterlist length is zero (no plaintext)
-decryption: input scatterlist contains only the mac
plus the condition of having different source and destination buffers
(or else scatterlist length = max(plaintext_len, ciphertext_len)).

These are not handled correctly, leading to crashes like:

root at p4080ds:~/crypto# insmod tcrypt.ko mode=45
------------[ cut here ]------------
kernel BUG at crypto/scatterwalk.c:37!
Oops: Exception in kernel mode, sig: 5 [#1]
SMP NR_CPUS=8 P4080 DS
Modules linked in: tcrypt(+) crc32c xts xcbc vmac pcbc ecb gcm ghash_generic gf128mul ccm ctr seqiv
CPU: 3 PID: 1082 Comm: cryptomgr_test Not tainted 3.11.0 #14
task: ee12c5b0 ti: eecd0000 task.ti: eecd0000
NIP: c0204d98 LR: f9225848 CTR: c0204d80
REGS: eecd1b70 TRAP: 0700   Not tainted  (3.11.0)
MSR: 00029002 <CE,EE,ME>  CR: 22044022  XER: 20000000

GPR00: f9225c94 eecd1c20 ee12c5b0 eecd1c28 ee879400 ee879400 00000000 ee607464
GPR08: 00000001 00000001 00000000 006b0000 c0204d80 00000000 00000002 c0698e20
GPR16: ee987000 ee895000 fffffff4 ee879500 00000100 eecd1d58 00000001 00000000
GPR24: ee879400 00000020 00000000 00000000 ee5b2800 ee607430 00000004 ee607460
NIP [c0204d98] scatterwalk_start+0x18/0x30
LR [f9225848] get_data_to_compute+0x28/0x2f0 [ccm]
Call Trace:
[eecd1c20] [f9225974] get_data_to_compute+0x154/0x2f0 [ccm] (unreliable)
[eecd1c70] [f9225c94] crypto_ccm_auth+0x184/0x1d0 [ccm]
[eecd1cb0] [f9225d40] crypto_ccm_encrypt+0x60/0x2d0 [ccm]
[eecd1cf0] [c020d77c] __test_aead+0x3ec/0xe20
[eecd1e20] [c020f35c] test_aead+0x6c/0xe0
[eecd1e40] [c020f420] alg_test_aead+0x50/0xd0
[eecd1e60] [c020e5e4] alg_test+0x114/0x2e0
[eecd1ee0] [c020bd1c] cryptomgr_test+0x4c/0x60
[eecd1ef0] [c0047058] kthread+0xa8/0xb0
[eecd1f40] [c000eb0c] ret_from_kernel_thread+0x5c/0x64
Instruction dump:
0f080000 81290024 552807fe 0f080000 5529003a 4bffffb4 90830000 39400000
39000001 8124000c 2f890000 7d28579e <0f090000> 81240008 91230004 4e800020
---[ end trace 6d652dfcd1be37bd ]---

Cc: Jussi Kivilinna <jussi.kivilinna at mbnet.fi>
Signed-off-by: Horia Geanta <horia.geanta at freescale.com>
Signed-off-by: Herbert Xu <herbert at gondor.apana.org.au>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 crypto/ccm.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/crypto/ccm.c b/crypto/ccm.c
index 32fe1bb..18d64ad 100644
--- a/crypto/ccm.c
+++ b/crypto/ccm.c
@@ -271,7 +271,8 @@ static int crypto_ccm_auth(struct aead_request *req, struct scatterlist *plain,
 	}

 	/* compute plaintext into mac */
-	get_data_to_compute(cipher, pctx, plain, cryptlen);
+	if (cryptlen)
+		get_data_to_compute(cipher, pctx, plain, cryptlen);

 out:
 	return err;
--
1.8.3.2