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    Subject[PATCH 5.18 719/879] wifi: mac80211: fix use-after-free in chanctx code
    Date
    From: Johannes Berg <johannes.berg@intel.com>

    commit 2965c4cdf7ad9ce0796fac5e57debb9519ea721e upstream.

    In ieee80211_vif_use_reserved_context(), when we have an
    old context and the new context's replace_state is set to
    IEEE80211_CHANCTX_REPLACE_NONE, we free the old context
    in ieee80211_vif_use_reserved_reassign(). Therefore, we
    cannot check the old_ctx anymore, so we should set it to
    NULL after this point.

    However, since the new_ctx replace state is clearly not
    IEEE80211_CHANCTX_REPLACES_OTHER, we're not going to do
    anything else in this function and can just return to
    avoid accessing the freed old_ctx.

    Cc: stable@vger.kernel.org
    Fixes: 5bcae31d9cb1 ("mac80211: implement multi-vif in-place reservations")
    Signed-off-by: Johannes Berg <johannes.berg@intel.com>
    Signed-off-by: Kalle Valo <kvalo@kernel.org>
    Link: https://lore.kernel.org/r/20220601091926.df419d91b165.I17a9b3894ff0b8323ce2afdb153b101124c821e5@changeid
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/mac80211/chan.c | 7 ++-----
    1 file changed, 2 insertions(+), 5 deletions(-)

    --- a/net/mac80211/chan.c
    +++ b/net/mac80211/chan.c
    @@ -1749,12 +1749,9 @@ int ieee80211_vif_use_reserved_context(s

    if (new_ctx->replace_state == IEEE80211_CHANCTX_REPLACE_NONE) {
    if (old_ctx)
    - err = ieee80211_vif_use_reserved_reassign(sdata);
    - else
    - err = ieee80211_vif_use_reserved_assign(sdata);
    + return ieee80211_vif_use_reserved_reassign(sdata);

    - if (err)
    - return err;
    + return ieee80211_vif_use_reserved_assign(sdata);
    }

    /*

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