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| author | Takashi Iwai <tiwai@suse.de> | 2017-10-09 11:02:56 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-10-18 10:20:42 +0300 |
| commit | ca2523c9c569186e1e39f5f9db6b593d3f4ccf87 (patch) | |
| tree | 516529db5029c8304902f9c687dfbb1863c98795 /include | |
| parent | 23709ae9b61429502fcd4686e7a97333f3b3544a (diff) | |
| download | linux-ca2523c9c569186e1e39f5f9db6b593d3f4ccf87.tar.xz | |
ALSA: seq: Fix copy_from_user() call inside lock
commit 5803b023881857db32ffefa0d269c90280a67ee0 upstream.
The event handler in the virmidi sequencer code takes a read-lock for
the linked list traverse, while it's calling snd_seq_dump_var_event()
in the loop. The latter function may expand the user-space data
depending on the event type. It eventually invokes copy_from_user(),
which might be a potential dead-lock.
The sequencer core guarantees that the user-space data is passed only
with atomic=0 argument, but snd_virmidi_dev_receive_event() ignores it
and always takes read-lock(). For avoiding the problem above, this
patch introduces rwsem for non-atomic case, while keeping rwlock for
atomic case.
Also while we're at it: the superfluous irq flags is dropped in
snd_virmidi_input_open().
Reported-by: Jia-Ju Bai <baijiaju1990@163.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/sound/seq_virmidi.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/include/sound/seq_virmidi.h b/include/sound/seq_virmidi.h index a03acd0d398a..695257ae64ac 100644 --- a/include/sound/seq_virmidi.h +++ b/include/sound/seq_virmidi.h @@ -60,6 +60,7 @@ struct snd_virmidi_dev { int port; /* created/attached port */ unsigned int flags; /* SNDRV_VIRMIDI_* */ rwlock_t filelist_lock; + struct rw_semaphore filelist_sem; struct list_head filelist; }; |