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authorVivien Didelot <vivien.didelot@gmail.com>2019-06-03 16:57:13 -0400
committerDavid S. Miller <davem@davemloft.net>2019-06-05 17:15:27 -0700
commit0ee4e76937d69128a6a66861ba393ebdc2ffc8a2 (patch)
treeaf339fbc4798df5ef78a3c3241327ef8c3556999 /net/core
parent0a8dd9f67cd0da7dc284f48b032ce00db1a68791 (diff)
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 <vivien.didelot@gmail.com> Reviewed-by: Michal Kubecek <mkubecek@suse.cz> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/core')
-rw-r--r--net/core/ethtool.c5
1 files changed, 4 insertions, 1 deletions
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, &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;