This is a note to let you know that I've just added the patch titled

crypto: n2 - cure use after free

to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: crypto-n2-cure-use-after-free.patch and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From 203f45003a3d03eea8fa28d74cfc74c354416fdb Mon Sep 17 00:00:00 2001

From: Jan Engelhardt jengelh@inai.de Date: Tue, 19 Dec 2017 19:09:07 +0100 Subject: crypto: n2 - cure use after free

From: Jan Engelhardt jengelh@inai.de

commit 203f45003a3d03eea8fa28d74cfc74c354416fdb upstream.

queue_cache_init is first called for the Control Word Queue (n2_crypto_probe). At that time, queue_cache[0] is NULL and a new kmem_cache will be allocated. If the subsequent n2_register_algs call fails, the kmem_cache will be released in queue_cache_destroy, but queue_cache_init[0] is not set back to NULL.

So when the Module Arithmetic Unit gets probed next (n2_mau_probe), queue_cache_init will not allocate a kmem_cache again, but leave it as its bogus value, causing a BUG() to trigger when queue_cache[0] is eventually passed to kmem_cache_zalloc:

n2_crypto: Found N2CP at /virtual-devices@100/n2cp@7 n2_crypto: Registered NCS HVAPI version 2.0 called queue_cache_init n2_crypto: md5 alg registration failed n2cp f028687c: /virtual-devices@100/n2cp@7: Unable to register algorithms. called queue_cache_destroy n2cp: probe of f028687c failed with error -22 n2_crypto: Found NCP at /virtual-devices@100/ncp@6 n2_crypto: Registered NCS HVAPI version 2.0 called queue_cache_init kernel BUG at mm/slab.c:2993! Call Trace: [0000000000604488] kmem_cache_alloc+0x1a8/0x1e0 (inlined) kmem_cache_zalloc (inlined) new_queue (inlined) spu_queue_setup (inlined) handle_exec_unit [0000000010c61eb4] spu_mdesc_scan+0x1f4/0x460 [n2_crypto] [0000000010c62b80] n2_mau_probe+0x100/0x220 [n2_crypto] [000000000084b174] platform_drv_probe+0x34/0xc0

Signed-off-by: Jan Engelhardt jengelh@inai.de Acked-by: David S. Miller davem@davemloft.net Signed-off-by: Herbert Xu herbert@gondor.apana.org.au Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- drivers/crypto/n2_core.c | 3 +++ 1 file changed, 3 insertions(+)

--- a/drivers/crypto/n2_core.c +++ b/drivers/crypto/n2_core.c @@ -1641,6 +1641,7 @@ static int queue_cache_init(void) CWQ_ENTRY_SIZE, 0, NULL); if (!queue_cache[HV_NCS_QTYPE_CWQ - 1]) { kmem_cache_destroy(queue_cache[HV_NCS_QTYPE_MAU - 1]); + queue_cache[HV_NCS_QTYPE_MAU - 1] = NULL; return -ENOMEM; } return 0; @@ -1650,6 +1651,8 @@ static void queue_cache_destroy(void) { kmem_cache_destroy(queue_cache[HV_NCS_QTYPE_MAU - 1]); kmem_cache_destroy(queue_cache[HV_NCS_QTYPE_CWQ - 1]); + queue_cache[HV_NCS_QTYPE_MAU - 1] = NULL; + queue_cache[HV_NCS_QTYPE_CWQ - 1] = NULL; }

static int spu_queue_register(struct spu_queue *p, unsigned long q_type)

Patches currently in stable-queue which might be from jengelh@inai.de are

queue-4.4/crypto-n2-cure-use-after-free.patch