commit 67ae7cf1eeda777f79259c4c6cb17a0bd28dee71
author Ben Hutchings <bhutchings@solarflare.com> Thu Jul 21 15:25:30 2011 -0700
committer David S. Miller <davem@davemloft.net> Thu Jul 21 15:25:30 2011 -0700
tree 3644c9018a246df166b220b35d6073efa48a385c
parent 1511022c9aabf253253e35730a6a3b945a2a53a9

ethtool: Allow zero-length register dumps again

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>
Cc: stable@kernel.org [2.6.37+]
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/ethtool.c

diff --git a/net/core/ethtool.c b/net/core/ethtool.c
index b7c12a6..6cdba5f 100644
--- a/net/core/ethtool.c
+++ b/net/core/ethtool.c
@@ -923,7 +923,7 @@
 		regs.len = reglen;
 
 	regbuf = vzalloc(reglen);
-	if (!regbuf)
+	if (reglen && !regbuf)
 		return -ENOMEM;
 
 	ops->get_regs(dev, &regs, regbuf);
@@ -932,7 +932,7 @@
 	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;