Re: [PATCH] net: mac80211: Add NULL checks for sta->sdata

Jia-Ju Bai <baijiaju@xxxxxxxxxxx> · Tue, 21 Mar 2023 17:37:06 +0800

On 2023/3/21 16:36, Simon Horman wrote:
However, in the same call stack, sta->sdata is also used in the
following functions:

ieee80211_ba_session_work()
    ___ieee80211_stop_rx_ba_session(sta)
      ht_dbg(sta->sdata, ...); -> No check
      sdata_info(sta->sdata, ...); -> No check
      ieee80211_send_delba(sta->sdata, ...) -> No check
    ___ieee80211_start_rx_ba_session(sta)
      ht_dbg(sta->sdata, ...); -> No check
      ht_dbg_ratelimited(sta->sdata, ...); -> No check
    ieee80211_tx_ba_session_handle_start(sta)
      sdata = sta->sdata; if (!sdata) -> Add check by previous commit
    ___ieee80211_stop_tx_ba_session(sdata)
      ht_dbg(sta->sdata, ...); -> No check
    ieee80211_start_tx_ba_cb(sdata)
      sdata = sta->sdata; local = sdata->local -> No check
    ieee80211_stop_tx_ba_cb(sdata)
      ht_dbg(sta->sdata, ...); -> No check
I wonder if it would be better to teach ht_* do do nothing
if the first argument is NULL.
Okay, I will use this way in patch v2.
Maybe it is not a good idea.
But I think it is worth trying, at least locally, to see how it goes.

After checking the code, I find that ht_* is actually a macro from _sdata_*.
Many code points use ht_* and _sdata_*, and thus I am not sure it is 
fine to try this way.

For simplification, I still think checking sdata before the calls to 
ht_* or _sdata_* should be more proper :)

Also, are these theoretical bugs?
Or something that has been observed?
And has a reproducer?
These bugs are found by my static analysis tool, by extending a known bug
fixed in a previous commit 69403bad97aa.
Thus, they could be theoretical bugs.
Thanks, understood.
I think it would be worth making that a bit clearer in the
patch description (commit message).

Okay.

I have sent the v2 patch, please have a look.
Thanks a lot :)

Best wishes,
Jia-Ju Bai