linux-kernel - [PATCH] sparc64: viohs: Remove VLA usage

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Message-ID: <20180905220351.GA48213@beast>
Date:   Wed, 5 Sep 2018 15:03:51 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "David S. Miller" <davem@...emloft.net>
Cc:     Allen Pais <allen.pais@...cle.com>,
        Philippe Ombredanne <pombredanne@...b.com>,
        sparclinux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] sparc64: viohs: Remove VLA usage

In the quest to remove all stack VLA usage from the kernel[1], this
allocates a fixed size array for the maximum number of cookies and
adds a runtime sanity check.

[1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1
RqZWA@...l.gmail.com

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 arch/sparc/kernel/viohs.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/arch/sparc/kernel/viohs.c b/arch/sparc/kernel/viohs.c
index 635d67ffc9a3..7db5aabe9708 100644
--- a/arch/sparc/kernel/viohs.c
+++ b/arch/sparc/kernel/viohs.c
@@ -180,11 +180,17 @@ static int send_dreg(struct vio_driver_state *vio)
 		struct vio_dring_register pkt;
 		char all[sizeof(struct vio_dring_register) +
 			 (sizeof(struct ldc_trans_cookie) *
-			  dr->ncookies)];
+			  VIO_MAX_RING_COOKIES)];
 	} u;
+	size_t bytes = sizeof(struct vio_dring_register) +
+		       (sizeof(struct ldc_trans_cookie) *
+			dr->ncookies);
 	int i;
 
-	memset(&u, 0, sizeof(u));
+	if (WARN_ON(bytes > sizeof(u)))
+		return -EINVAL;
+
+	memset(&u, 0, bytes);
 	init_tag(&u.pkt.tag, VIO_TYPE_CTRL, VIO_SUBTYPE_INFO, VIO_DRING_REG);
 	u.pkt.dring_ident = 0;
 	u.pkt.num_descr = dr->num_entries;
@@ -206,7 +212,7 @@ static int send_dreg(struct vio_driver_state *vio)
 		       (unsigned long long) u.pkt.cookies[i].cookie_size);
 	}
 
-	return send_ctrl(vio, &u.pkt.tag, sizeof(u));
+	return send_ctrl(vio, &u.pkt.tag, bytes);
 }
 
 static int send_rdx(struct vio_driver_state *vio)
-- 
2.17.1


-- 
Kees Cook
Pixel Security