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ALSA: seq: Fix data-race at module auto-loading
commit 3e7e04b747
upstream.
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
parent
e7ee1f3c64
commit
f57ca0e2cd
1 changed files with 5 additions and 7 deletions
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@ -136,13 +136,13 @@ struct snd_seq_client *snd_seq_client_use_ptr(int clientid)
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spin_unlock_irqrestore(&clients_lock, flags);
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#ifdef CONFIG_MODULES
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if (!in_interrupt()) {
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static char client_requested[SNDRV_SEQ_GLOBAL_CLIENTS];
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static char card_requested[SNDRV_CARDS];
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static DECLARE_BITMAP(client_requested, SNDRV_SEQ_GLOBAL_CLIENTS);
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static DECLARE_BITMAP(card_requested, SNDRV_CARDS);
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if (clientid < SNDRV_SEQ_GLOBAL_CLIENTS) {
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int idx;
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if (!client_requested[clientid]) {
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client_requested[clientid] = 1;
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if (!test_and_set_bit(clientid, client_requested)) {
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for (idx = 0; idx < 15; idx++) {
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if (seq_client_load[idx] < 0)
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break;
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@ -157,10 +157,8 @@ struct snd_seq_client *snd_seq_client_use_ptr(int clientid)
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int card = (clientid - SNDRV_SEQ_GLOBAL_CLIENTS) /
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SNDRV_SEQ_CLIENTS_PER_CARD;
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if (card < snd_ecards_limit) {
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if (! card_requested[card]) {
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card_requested[card] = 1;
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if (!test_and_set_bit(card, card_requested))
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snd_request_card(card);
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}
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snd_seq_device_load_drivers();
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}
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}
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