Messages in this thread | | | Subject | Re: [PATCH] ethtool: fix a potential missing-check bug | From | Shannon Nelson <> | Date | Mon, 30 Apr 2018 09:46:51 -0700 |
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On 4/29/2018 6:31 PM, Wenwen Wang wrote: > 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 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 <wang6495@umn.edu> > --- > net/core/ethtool.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/net/core/ethtool.c b/net/core/ethtool.c > index 03416e6..a121034 100644 > --- a/net/core/ethtool.c > +++ b/net/core/ethtool.c > @@ -1032,6 +1032,8 @@ 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;
You might add a comment here to explain why the second check; otherwise someone might come along later and remove this check as redundant code.
sln
> + if (!(info.flow_type & FLOW_RSS)) > + return -EINVAL; > } > > if (info.cmd == ETHTOOL_GRXCLSRLALL) { >
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