netdev - [PATCH net-next] ethtool: copy reglen to userspace

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Message-Id: <20190528205848.21208-1-vivien.didelot@gmail.com>
Date:   Tue, 28 May 2019 16:58:48 -0400
From:   Vivien Didelot <vivien.didelot@...il.com>
To:     netdev@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, kernel@...oirfairelinux.com,
        Vivien Didelot <vivien.didelot@...il.com>,
        "David S. Miller" <davem@...emloft.net>, linville@...hat.com,
        f.fainelli@...il.com
Subject: [PATCH net-next] ethtool: copy reglen to userspace

ethtool_get_regs() allocates a buffer of size reglen obtained from
ops->get_regs_len(), thus only this value must be used when copying
the buffer back to userspace. Also no need to check regbuf twice.

Signed-off-by: Vivien Didelot <vivien.didelot@...il.com>
---
 net/core/ethtool.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/ethtool.c b/net/core/ethtool.c
index 4a593853cbf2..f3369f31d93a 100644
--- a/net/core/ethtool.c
+++ b/net/core/ethtool.c
@@ -1338,38 +1338,38 @@ static noinline_for_stack int ethtool_set_rxfh(struct net_device *dev,
 static int ethtool_get_regs(struct net_device *dev, char __user *useraddr)
 {
 	struct ethtool_regs regs;
 	const struct ethtool_ops *ops = dev->ethtool_ops;
 	void *regbuf;
 	int reglen, ret;
 
 	if (!ops->get_regs || !ops->get_regs_len)
 		return -EOPNOTSUPP;
 
 	if (copy_from_user(&regs, useraddr, sizeof(regs)))
 		return -EFAULT;
 
 	reglen = ops->get_regs_len(dev);
 	if (reglen <= 0)
 		return reglen;
 
 	if (regs.len > reglen)
 		regs.len = reglen;
 
 	regbuf = vzalloc(reglen);
 	if (!regbuf)
 		return -ENOMEM;
 
 	ops->get_regs(dev, &regs, regbuf);
 
 	ret = -EFAULT;
 	if (copy_to_user(useraddr, &regs, sizeof(regs)))
 		goto out;
 	useraddr += offsetof(struct ethtool_regs, data);
-	if (regbuf && copy_to_user(useraddr, regbuf, regs.len))
+	if (copy_to_user(useraddr, regbuf, reglen))
 		goto out;
 	ret = 0;
 
  out:
 	vfree(regbuf);
 	return ret;
 }
-- 
2.21.0