From: Ben Hutchings <bhutchings@solarflare.com>
Date: Thu, 21 Jul 2011 22:25:30 +0000 (-0700)
Subject: ethtool: Allow zero-length register dumps again
X-Git-Tag: firefly_0821_release~7541^2~3096
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=3de8ae6c0d1c0fb73243992adf87c7174028a531;p=firefly-linux-kernel-4.4.55.git

ethtool: Allow zero-length register dumps again

commit 67ae7cf1eeda777f79259c4c6cb17a0bd28dee71 upstream.

Some drivers (ab)use the ethtool_ops::get_regs operation to expose
only a hardware revision ID.  Commit
a77f5db361ed9953b5b749353ea2c7fed2bf8d93 ('ethtool: Allocate register
dump buffer with vmalloc()') had the side-effect of breaking these, as
vmalloc() returns a null pointer for size=0 whereas kmalloc() did not.

For backward-compatibility, allow zero-length dumps again.

Reported-by: Kalle Valo <kvalo@qca.qualcomm.com>
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---

diff --git a/net/core/ethtool.c b/net/core/ethtool.c
index fd14116ad7f0..4fb77049e83d 100644
--- a/net/core/ethtool.c
+++ b/net/core/ethtool.c
@@ -1227,7 +1227,7 @@ static int ethtool_get_regs(struct net_device *dev, char __user *useraddr)
 		regs.len = reglen;
 
 	regbuf = vzalloc(reglen);
-	if (!regbuf)
+	if (reglen && !regbuf)
 		return -ENOMEM;
 
 	ops->get_regs(dev, &regs, regbuf);
@@ -1236,7 +1236,7 @@ static int ethtool_get_regs(struct net_device *dev, char __user *useraddr)
 	if (copy_to_user(useraddr, &regs, sizeof(regs)))
 		goto out;
 	useraddr += offsetof(struct ethtool_regs, data);
-	if (copy_to_user(useraddr, regbuf, regs.len))
+	if (regbuf && copy_to_user(useraddr, regbuf, regs.len))
 		goto out;
 	ret = 0;