Tetsuo Handa [off-list ref] wrote:

syzbot is reporting that del_timer_sync() is called from
mwifiex_usb_cleanup_tx_aggr() from mwifiex_unregister_dev() without
checking timer_setup() from mwifiex_usb_tx_init() was called [1].

Ganapathi Bhat proposed a possibly cleaner fix, but it seems that
that fix was forgotten [2].

"grep -FrB1 'del_timer' drivers/ | grep -FA1 '.function)'" says that
currently there are 28 locations which call del_timer[_sync]() only if
that timer's function field was initialized (because timer_setup() sets
that timer's function field). Therefore, let's use same approach here.

[1] https://syzkaller.appspot.com/bug?id=26525f643f454dd7be0078423e3cdb0d57744959
[2] https://lkml.kernel.org/r/CA+ASDXMHt2gq9Hy+iP_BYkWXsSreWdp3_bAfMkNcuqJ3K+-jbQ@mail.gmail.com

Reported-by: syzbot <redacted>
Cc: Ganapathi Bhat <redacted>
Cc: Brian Norris <briannorris@chromium.org>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reviewed-by: Brian Norris <briannorris@chromium.org>
Acked-by: Ganapathi Bhat <redacted>

Patch applied to wireless-drivers-next.git, thanks.

621a3a8b1c0e mwifiex: don't call del_timer_sync() on uninitialized timer

-- 
https://patchwork.kernel.org/patch/11728607/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches