On Tue, Apr 04, 2023 at 05:58:13PM +0800, Jia-Ju Bai wrote:
> Hi Simon,
>
> Thanks for your reply, and sorry for the delay.
>
> On 2023/3/26 23:05, Simon Horman wrote:
> > On Tue, Mar 21, 2023 at 05:31:22PM +0800, Jia-Ju Bai wrote:
> > > In a previous commit 69403bad97aa ("wifi: mac80211: sdata can be NULL
> > > during AMPDU start"), sta->sdata can be NULL, and thus it should be
> > > checked before being used.
> > >
> > > 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
> > >
> > > Thus, to avoid possible null-pointer dereferences, the related checks
> > > should be added.
> > >
> > > These bugs are reported by a static analysis tool implemented by myself,
> > > and they are found by extending a known bug fixed in the previous commit.
> > > Thus, they could be theoretical bugs.
> > >
> > > Signed-off-by: Jia-Ju Bai <baijiaju@xxxxxxxxxxx>
> > > ---
> > > v2:
> > > * Fix an error reported by checkpatch.pl, and make the bug finding
> > > process more clear in the description. Thanks for Simon's advice.
> > > ---
> > > net/mac80211/agg-rx.c | 68 ++++++++++++++++++++++++++-----------------
> > > net/mac80211/agg-tx.c | 16 ++++++++--
> > > 2 files changed, 55 insertions(+), 29 deletions(-)
> > >
> > > diff --git a/net/mac80211/agg-rx.c b/net/mac80211/agg-rx.c
> > > index c6fa53230450..6616970785a2 100644
> > > --- a/net/mac80211/agg-rx.c
> > > +++ b/net/mac80211/agg-rx.c
> > > @@ -80,19 +80,21 @@ void ___ieee80211_stop_rx_ba_session(struct sta_info *sta, u16 tid,
> > > RCU_INIT_POINTER(sta->ampdu_mlme.tid_rx[tid], NULL);
> > > __clear_bit(tid, sta->ampdu_mlme.agg_session_valid);
> > > - ht_dbg(sta->sdata,
> > > - "Rx BA session stop requested for %pM tid %u %s reason: %d\n", > - sta->sta.addr, tid,
> > > - initiator == WLAN_BACK_RECIPIENT ? "recipient" : "initiator",
> > > - (int)reason);
> > > + if (sta->sdata) {
> > > + ht_dbg(sta->sdata,
> > > + "Rx BA session stop requested for %pM tid %u %s reason: %d\n",
> > > + sta->sta.addr, tid,
> > > + initiator == WLAN_BACK_RECIPIENT ? "recipient" : "initiator",
> > > + (int)reason);
> > > + }
> > The first line of the body of ___ieee80211_stop_rx_ba_session() is:
> >
> > struct ieee80211_local *local = sta->sdata->local;
> >
> > So a NULL pointer dereference will have occurred before
> > the checks this change adds to that function.
>
> I checked the source code again (including the latest version 6.3-rc5).
> The first line of the body of ___ieee80211_stop_rx_ba_session() is:
>
> struct ieee80211_local *local = sta->local;
>
> Thus, there is no dereference of sta->sdata.
My mistake, sorry about that.
> In a different function, namely ___ieee80211_start_rx_ba_session(), the
> first line is:
>
> struct ieee80211_local *local = sta->sdata->local;
Yes, I see that too.
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