From 0ee4e76937d69128a6a66861ba393ebdc2ffc8a2 Mon Sep 17 00:00:00 2001 From: Vivien Didelot Date: Mon, 3 Jun 2019 16:57:13 -0400 Subject: [PATCH] ethtool: fix potential userspace buffer overflow ethtool_get_regs() allocates a buffer of size ops->get_regs_len(), and pass it to the kernel driver via ops->get_regs() for filling. There is no restriction about what the kernel drivers can or cannot do with the open ethtool_regs structure. They usually set regs->version and ignore regs->len or set it to the same size as ops->get_regs_len(). But if userspace allocates a smaller buffer for the registers dump, we would cause a userspace buffer overflow in the final copy_to_user() call, which uses the regs.len value potentially reset by the driver. To fix this, make this case obvious and store regs.len before calling ops->get_regs(), to only copy as much data as requested by userspace, up to the value returned by ops->get_regs_len(). While at it, remove the redundant check for non-null regbuf. Signed-off-by: Vivien Didelot Reviewed-by: Michal Kubecek Signed-off-by: David S. Miller --- net/core/ethtool.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/net/core/ethtool.c b/net/core/ethtool.c index 43e9add58340..1a0196fbb49c 100644 --- a/net/core/ethtool.c +++ b/net/core/ethtool.c @@ -1359,13 +1359,16 @@ static int ethtool_get_regs(struct net_device *dev, char __user *useraddr) if (!regbuf) return -ENOMEM; + if (regs.len < reglen) + reglen = regs.len; + ops->get_regs(dev, ®s, regbuf); ret = -EFAULT; if (copy_to_user(useraddr, ®s, 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; -- 2.30.2