From: Johannes Berg <johannes@xxxxxxxxxxxxxxxx> Date: Tue, 05 Dec 2017 17:34:21 +0100 > On Tue, 2017-12-05 at 11:31 -0500, David Miller wrote: >> >> > We could try to fix up the big endian problem here, but we >> > don't know *how* userspace misbehaved - if using nla_put_u32 >> > then we could, but we also found a debug tool (which we'll >> > ignore for the purposes of this regression) that was putting >> > the padding into the length. > >> We're stuck with this thing forever... I'd like to consider other >> options. >> >> I've seen this problem at least one time before, therefore I >> suggest when we see a U8 attribute with a U32's length: >> >> 1) We access it as a u32, this takes care of all endianness >> issues. > > Possible, but as I said above, I've seen at least one tool (a debug > only script) now that will actually emit a U8 followed by 3 bytes of > padding to make it netlink-aligned, but set the length to 4. That would > be broken by making this change. There is no reasonable interpretation for what that application is doing, so I think we can safely call that case as buggy. We are only trying to handle the situation where a U8 attribute is presented as a bonafide U32 or a correct U8. Does this make sense?
