linux-kernel - [PATCH 3.12 020/101] hwrng: pseries - port to new read API and fix stack corruption

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <50e52368e667f2a8d5a43c0c9f60b4391a5bc715.1417605922.git.jslaby@suse.cz>
Date:	Wed,  3 Dec 2014 12:25:42 +0100
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Greg Kurz <gkurz@...ux.vnet.ibm.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 020/101] hwrng: pseries - port to new read API and fix stack corruption

From: Greg Kurz <gkurz@...ux.vnet.ibm.com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit 24c65bc7037e7d0f362c0df70d17dd72ee64b8b9 upstream.

The add_early_randomness() function in drivers/char/hw_random/core.c passes
a 16-byte buffer to pseries_rng_data_read(). Unfortunately, plpar_hcall()
returns four 64-bit values and trashes 16 bytes on the stack.

This bug has been lying around for a long time. It got unveiled by:

commit d3cc7996473a7bdd33256029988ea690754e4e2a
Author: Amit Shah <amit.shah@...hat.com>
Date:   Thu Jul 10 15:42:34 2014 +0530

    hwrng: fetch randomness only after device init

It may trig a oops while loading or unloading the pseries-rng module for both
PowerVM and PowerKVM guests.

This patch does two things:
- pass an intermediate well sized buffer to plpar_hcall(). This is acceptalbe
  since we're not on a hot path.
- move to the new read API so that we know the return buffer size for sure.

Signed-off-by: Greg Kurz <gkurz@...ux.vnet.ibm.com>
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 drivers/char/hw_random/pseries-rng.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/char/hw_random/pseries-rng.c b/drivers/char/hw_random/pseries-rng.c
index b761459a3436..ab11c16352f8 100644
--- a/drivers/char/hw_random/pseries-rng.c
+++ b/drivers/char/hw_random/pseries-rng.c
@@ -26,18 +26,21 @@
 
 #define MODULE_NAME "pseries-rng"
 
-static int pseries_rng_data_read(struct hwrng *rng, u32 *data)
+static int pseries_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
 {
+	u64 buffer[PLPAR_HCALL_BUFSIZE];
+	size_t size = max < 8 ? max : 8;
 	int rc;
 
-	rc = plpar_hcall(H_RANDOM, (unsigned long *)data);
+	rc = plpar_hcall(H_RANDOM, (unsigned long *)buffer);
 	if (rc != H_SUCCESS) {
 		pr_err_ratelimited("H_RANDOM call failed %d\n", rc);
 		return -EIO;
 	}
+	memcpy(data, buffer, size);
 
 	/* The hypervisor interface returns 64 bits */
-	return 8;
+	return size;
 }
 
 /**
@@ -56,7 +59,7 @@ static unsigned long pseries_rng_get_desired_dma(struct vio_dev *vdev)
 
 static struct hwrng pseries_rng = {
 	.name		= MODULE_NAME,
-	.data_read	= pseries_rng_data_read,
+	.read		= pseries_rng_read,
 };
 
 static int __init pseries_rng_probe(struct vio_dev *dev,
-- 
2.1.3

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/