In ethtool_get_rxnfc(), the object "info" is firstly copied from
user-space. If the FLOW_RSS flag is set in the member field flow_type of
"info" (and cmd is ETHTOOL_GRXFH), info needs to be copied again from
user-space because FLOW_RSS is newer and has new definition, as mentioned
in the comment. However, given that the user data resides in user-space, a
malicious user can race to change the data after the first copy. By doing
so, the user can inject inconsistent data. For example, in the second
copy, the FLOW_RSS flag could be cleared in the field flow_type of "info".
In the following execution, "info" will be used in the function
ops->get_rxnfc(). Such inconsistent data can potentially lead to unexpected
information leakage since ops->get_rxnfc() will prepare various types of
data according to flow_type, and the prepared data will be eventually
copied to user-space. This inconsistent data may also cause undefined
behaviors based on how ops->get_rxnfc() is implemented.
This patch simply re-verifies the flow_type field of "info" after the
second copy. If the value is not as expected, an error code will be
returned.
Signed-off-by: Wenwen Wang <[email protected]>
---
net/core/ethtool.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/net/core/ethtool.c b/net/core/ethtool.c
index 03416e6..ba02f0d 100644
--- a/net/core/ethtool.c
+++ b/net/core/ethtool.c
@@ -1032,6 +1032,11 @@ static noinline_for_stack int ethtool_get_rxnfc(struct net_device *dev,
info_size = sizeof(info);
if (copy_from_user(&info, useraddr, info_size))
return -EFAULT;
+ /* Since malicious users may modify the original data,
+ * we need to check whether FLOW_RSS is still requested.
+ */
+ if (!(info.flow_type & FLOW_RSS))
+ return -EINVAL;
}
if (info.cmd == ETHTOOL_GRXCLSRLALL) {
--
2.7.4
From: Wenwen Wang <[email protected]>
Date: Mon, 30 Apr 2018 12:31:13 -0500
> In ethtool_get_rxnfc(), the object "info" is firstly copied from
> user-space. If the FLOW_RSS flag is set in the member field flow_type of
> "info" (and cmd is ETHTOOL_GRXFH), info needs to be copied again from
> user-space because FLOW_RSS is newer and has new definition, as mentioned
> in the comment. However, given that the user data resides in user-space, a
> malicious user can race to change the data after the first copy. By doing
> so, the user can inject inconsistent data. For example, in the second
> copy, the FLOW_RSS flag could be cleared in the field flow_type of "info".
> In the following execution, "info" will be used in the function
> ops->get_rxnfc(). Such inconsistent data can potentially lead to unexpected
> information leakage since ops->get_rxnfc() will prepare various types of
> data according to flow_type, and the prepared data will be eventually
> copied to user-space. This inconsistent data may also cause undefined
> behaviors based on how ops->get_rxnfc() is implemented.
>
> This patch simply re-verifies the flow_type field of "info" after the
> second copy. If the value is not as expected, an error code will be
> returned.
>
> Signed-off-by: Wenwen Wang <[email protected]>
Applied, thanks.