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Wed, 7 Oct 2026 17:20:55 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id 8rcALXZ/xmp1CgAAD6G6ig:T9 (envelope-from ); Wed, 07 Oct 2026 17:20:55 +0000 From: Takashi Iwai To: linux-sound@vger.kernel.org Cc: linux-kernel@vger.kernel.org Subject: [PATCH v3 8/8] ALSA: core: Add missing barriers for power_ref vs card->shutdown Date: Wed, 7 Oct 2026 19:20:44 +0200 Message-ID: <20261007172051.13240-9-tiwai@suse.de> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20261007172051.13240-1-tiwai@suse.de> References: <20261007172051.13240-1-tiwai@suse.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spam-Flag: NO X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Spamd-Result: default: False [-3.01 / 50.00]; BAYES_HAM(-3.00)[100.00%]; MID_CONTAINS_FROM(1.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_MISSING_CHARSET(0.50)[]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; DNSWL_BLOCKED(0.00)[2a07:de40:b281:104:10:150:64:97:from,2a07:de40:b281:106:10:150:64:167:received]; RCVD_VIA_SMTP_AUTH(0.00)[]; MIME_TRACE(0.00)[0:+]; ARC_NA(0.00)[]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; RCPT_COUNT_TWO(0.00)[2]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,imap1.dmz-prg2.suse.org:rdns,suse.de:email,suse.de:dkim]; RCVD_TLS_ALL(0.00)[]; TO_DN_NONE(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DKIM_TRACE(0.00)[suse.de:+] X-Rspamd-Action: no action X-Spam-Score: -3.01 X-Spam-Level: X-Rspamd-Queue-Id: DD50B1F44F snd_power_ref_and_wait() increments card->power_ref and then reads card->shutdown (and the power state) locklessly, while snd_card_disconnect() sets card->shutdown and then waits for power_ref to drop to zero via snd_power_sync_ref(). Due to the missing barrier on both sides, the caller proceeds with shutdown still seen as false, while the disconnect side sees a zero refcount and continues tearing down incorrectly. For addressing the potential race, add smp_mb__after_atomic() after the refcount increment and smp_mb() before snd_power_sync_ref() in snd_card_disconnect(). Fixes: e94fdbd7b25d ("ALSA: control: Track in-flight control read/write/tlv accesses") Reported-by: Sashiko Assisted-by: LLM Signed-off-by: Takashi Iwai --- sound/core/init.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/sound/core/init.c b/sound/core/init.c index 7878c0e6103c..dbe2acfa59fe 100644 --- a/sound/core/init.c +++ b/sound/core/init.c @@ -535,6 +535,8 @@ void snd_card_disconnect(struct snd_card *card) clear_bit(card->number, snd_cards_lock); } + /* order card->shutdown store against power_ref read */ + smp_mb(); snd_power_sync_ref(card); } EXPORT_SYMBOL(snd_card_disconnect); @@ -1152,6 +1154,8 @@ EXPORT_SYMBOL(snd_card_file_remove); int snd_power_ref_and_wait(struct snd_card *card) { snd_power_ref(card); + /* order power_ref increment against card->shutdown read */ + smp_mb__after_atomic(); if (snd_power_get_state(card) != SNDRV_CTL_POWER_D0) { wait_event_cmd(card->power_sleep, card->shutdown || -- 2.55.0