On Mon, May 26, 2025 at 05:19:03PM +0800, Wentao Liang wrote:
> The function ieee80211_chsw_switch_vifs() calls the function
> ieee80211_link_get_chanctx(), but does not check its return value.
> The return value is a null pointer if the ieee80211_link_get_chanctx()
> fails. This will lead to a null pointer dereference in the following
> code "&old_ctx->conf". A proper implementation can be found in
> ieee80211_link_use_reserved_assign().
>
> Add a null pointer check and goto error handling path if the
> function fails.
>
> Fixes: 5d52ee811019 ("mac80211: allow reservation of a running chanctx")
> Cc: stable@xxxxxxxxxxxxxxx # v3.16
> Signed-off-by: Wentao Liang <vulab@xxxxxxxxxxx>
> ---
> v2: Fix code error.
>
> net/mac80211/chan.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/net/mac80211/chan.c b/net/mac80211/chan.c
> index a442cb667520..c9b703c283e7 100644
> --- a/net/mac80211/chan.c
> +++ b/net/mac80211/chan.c
> @@ -1503,6 +1503,10 @@ static int ieee80211_chsw_switch_vifs(struct ieee80211_local *local,
> continue;
>
> old_ctx = ieee80211_link_get_chanctx(link);
> + if (WARN_ON(!old_ctx)) {
You just caused the machine to crash and reboot on billions of Linux
systems if this ever is triggered. So please never do that :(
thanks,
greg k-h
