[Readded Larry to the CC]
On Saturday, December 27, 2014 12:15:58 AM Christopher Chavez wrote:
> > My bisection led to a branch commit d17ec4d as the "bad" commit.
> > Rather than finding out where the bisection went bad, I added
> > code to check skb->tail, skb->end, and the length to be added.
> > At the time of the call that panics, there are 6 bytes between
> > tail and end with 8 bytes needed.
> >
> > I will be looking for the place where the driver calculates how
> > large the skb should be.
I think this narrows it down. However, I'm not 100% sure yet if the
problem is just because of "mac80211: don't resize skbs needlessly".
>From looking at a other patch from that time and context. I think: "
commit ca34e3b5c808385b175650605faa29e71e91991b
Author: Ido Yariv <ido@xxxxxxxxxx>
Date: Tue Jul 29 15:38:53 2014 +0300
mac80211: Fix accounting of the tailroom-needed counter [1]
When hw acceleration is enabled, the GENERATE_IV or PUT_IV_SPACE flags
will only require headroom space. Consequently, the tailroom-needed
counter can safely be decremented."
changed/broke things for p54* (note: cw1200 could be affected as well?
This driver also modifies the tailroom for skbs in cw1200_tx_h_crypt).
Previously, the driver didn't need to manage the tailroom. If the
IEEE80211_KEY_FLAG_GENERATE_IV flag was set, mac80211 would take care of
resizing the skb at the right time and just in one place [of course the
downside was that mac80211 did the resize needlessly].
I can think of several ways of dealing with this issue:
1. move the expand and trim tailroom into the driver.
AFAICT this would add an additional resize [at a bad time].
2. add extra IEEE80211_KEY_FLAG_ or HW_FLAG to restore the old behavior.
This should be possible and relatively simple. But we/I have to be
especially careful to differentiate properly between the old and new.
[i.e.: I need to know what the deal is behind:
IEEE80211_KEY_FLAG_GENERATE_IV_MGMT in this case? Looks like it can
be ignored?]
3. suggestions?
[No, I'm not going to touch crypto_tx_tailroom_needed_cnt outside of
mac80211 :D]
Regards,
Christian
[1] <http://www.spinics.net/lists/linux-wireless/msg125374.html>
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