linux-kernel - [PATCH 3.16 076/178] bna: integer overflow bug in debugfs

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Date:   Sun, 16 Jul 2017 14:56:46 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Rasesh Mody" <rasesh.mody@...ium.com>,
        "David S. Miller" <davem@...emloft.net>,
        "Dan Carpenter" <dan.carpenter@...cle.com>
Subject: [PATCH 3.16 076/178] bna: integer overflow bug in debugfs

3.16.46-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Dan Carpenter <dan.carpenter@...cle.com>

commit 13e2d5187f6b965ba3556caedb914baf81b98ed2 upstream.

We could allocate less memory than intended because we do:

	bnad->regdata = kzalloc(len << 2, GFP_KERNEL);

The shift can overflow leading to a crash.  This is debugfs code so the
impact is very small.

Fixes: 7afc5dbde091 ("bna: Add debugfs interface.")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
Acked-by: Rasesh Mody <rasesh.mody@...ium.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/net/ethernet/brocade/bna/bnad_debugfs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/net/ethernet/brocade/bna/bnad_debugfs.c
+++ b/drivers/net/ethernet/brocade/bna/bnad_debugfs.c
@@ -331,7 +331,7 @@ bnad_debugfs_write_regrd(struct file *fi
 	}
 
 	rc = sscanf(kern_buf, "%x:%x", &addr, &len);
-	if (rc < 2) {
+	if (rc < 2 || len > UINT_MAX >> 2) {
 		pr_warn("bna %s: Failed to read user buffer\n",
 			pci_name(bnad->pcidev));
 		kfree(kern_buf);