[PATCH v2 0/2] ASoC: soc-core: fix use-after-free in close_delayed_work

["matteo.cotifava" <cotifavamatteo@gmail.com>]

Fix a use-after-free in snd_soc_dapm_stream_event() triggered when a
sound card is unbound while a PCM close delayed work is pending.

As Mark pointed out in v1 review, flush_delayed_work() does handle
pending timers correctly. The actual issue appears to be new work
getting scheduled after the flush: snd_card_disconnect_sync() inside
soc_cleanup_card_resources() can trigger PCM closes which call
snd_soc_dapm_stream_stop(), scheduling new delayed work after the
flush in snd_soc_unbind_card() has already completed. If the timer
fires after soc_remove_link_components() frees the DAPM widgets,
the work accesses freed memory.

v1 -> v2:
- Split into two patches as requested
- Dropped cancel_delayed_work_sync() approach, kept flush as suggested
- Added a flush in soc_cleanup_card_resources() after disconnect_sync
  (so no new work can be scheduled) and before DAIs/widgets are freed

matteo.cotifava (2):
  ASoC: soc-core: drop delayed_work_pending() check before flush
  ASoC: soc-core: flush delayed work before removing DAIs and widgets

 sound/soc/soc-core.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

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2.39.5