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| author | Takashi Iwai <tiwai@suse.de> | 2022-08-23 10:27:17 +0300 |
|---|---|---|
| committer | Takashi Iwai <tiwai@suse.de> | 2022-08-24 08:59:06 +0300 |
| commit | 3e7e04b747adea36f349715d9f0998eeebf15d72 (patch) | |
| tree | 52bffb03307aa12eaa13ac76a801703759705473 /sound/core | |
| parent | 22dec134dbfa825b963f8a1807ad19b943e46a56 (diff) | |
| download | linux-3e7e04b747adea36f349715d9f0998eeebf15d72.tar.xz | |
ALSA: seq: Fix data-race at module auto-loading
It's been reported that there is a possible data-race accessing to the
global card_requested[] array at ALSA sequencer core, which is used
for determining whether to call request_module() for the card or not.
This data race itself is almost harmless, as it might end up with one
extra request_module() call for the already loaded module at most.
But it's still better to fix.
This patch addresses the possible data race of card_requested[] and
client_requested[] arrays by replacing them with bitmask.
It's an atomic operation and can work without locks.
Reported-by: Abhishek Shah <abhishek.shah@columbia.edu>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/CAEHB24_ay6YzARpA1zgCsE7=H9CSJJzux618E=Ka4h0YdKn=qA@mail.gmail.com
Link: https://lore.kernel.org/r/20220823072717.1706-2-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'sound/core')
| -rw-r--r-- | sound/core/seq/seq_clientmgr.c | 12 |
1 files changed, 5 insertions, 7 deletions
diff --git a/sound/core/seq/seq_clientmgr.c b/sound/core/seq/seq_clientmgr.c index 2e9d695d336c..2d707afa1ef1 100644 --- a/sound/core/seq/seq_clientmgr.c +++ b/sound/core/seq/seq_clientmgr.c @@ -121,13 +121,13 @@ struct snd_seq_client *snd_seq_client_use_ptr(int clientid) spin_unlock_irqrestore(&clients_lock, flags); #ifdef CONFIG_MODULES if (!in_interrupt()) { - static char client_requested[SNDRV_SEQ_GLOBAL_CLIENTS]; - static char card_requested[SNDRV_CARDS]; + static DECLARE_BITMAP(client_requested, SNDRV_SEQ_GLOBAL_CLIENTS); + static DECLARE_BITMAP(card_requested, SNDRV_CARDS); + if (clientid < SNDRV_SEQ_GLOBAL_CLIENTS) { int idx; - if (!client_requested[clientid]) { - client_requested[clientid] = 1; + if (!test_and_set_bit(clientid, client_requested)) { for (idx = 0; idx < 15; idx++) { if (seq_client_load[idx] < 0) break; @@ -142,10 +142,8 @@ struct snd_seq_client *snd_seq_client_use_ptr(int clientid) int card = (clientid - SNDRV_SEQ_GLOBAL_CLIENTS) / SNDRV_SEQ_CLIENTS_PER_CARD; if (card < snd_ecards_limit) { - if (! card_requested[card]) { - card_requested[card] = 1; + if (!test_and_set_bit(card, card_requested)) snd_request_card(card); - } snd_seq_device_load_drivers(); } } |