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Sat, 12 Sep 2026 16:21:53 +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 96k6DSF8pWpHZwAAD6G6ig (envelope-from ); Sat, 12 Sep 2026 16:21:53 +0000 From: Takashi Iwai To: linux-sound@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Farhad Alemi Subject: [PATCH v2] ALSA: core: Fix potential UAF after asynchronous card release Date: Sat, 12 Sep 2026 18:21:42 +0200 Message-ID: <20260912162150.455144-1-tiwai@suse.de> X-Mailer: git-send-email 2.55.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Spam-Score: -3.01 X-Rspamd-Queue-Id: 82F6921D61 X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Spam-Level: X-Rspamd-Action: no action X-Spamd-Result: default: False [-3.01 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; MID_CONTAINS_FROM(1.00)[]; 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)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,imap1.dmz-prg2.suse.org:rdns,suse.de:dkim,suse.de:email,suse.de:mid]; FROM_HAS_DN(0.00)[]; ARC_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; TO_DN_SOME(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; RCVD_TLS_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; FROM_EQ_ENVFROM(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; RCPT_COUNT_THREE(0.00)[3]; DKIM_TRACE(0.00)[suse.de:+] X-Spam-Flag: NO Content-Type: text/plain; charset="utf-8" Usually a sound driver releases the resources assigned to the card via snd_card_free(), and it synchronizes with the whole release procedure. However, when the card is released asynchronously via snd_card_free_when_closed() like USB-audio driver, the situation is slightly different; although the snd_card_disconnect() call at the disconnection guarantees that any newer accesses will be gated, the in-flight tasks might be still accessing to the underlying card->dev device even after the disconnection, which would cause a use-after-free in the end, as reported by fuzzers. For addressing the bug above, this patch takes the refcount of card->dev at initialization of the card object, and releases at its destructor. This assures the availability of the card->dev in its whole lifecycle. Reported-by: Farhad Alemi Closes: https://lore.kernel.org/CA+0ovChexj4TrZL_2iG_P0WBEbZc5+73GfB3DkciQi= =3DR8pZOnA@mail.gmail.com Closes: https://lore.kernel.org/CA+0ovCgQUQNN=3DZ1tJTouiCsDaXR5M-3-SQEGk-cp= PXQkM5Xh+w@mail.gmail.com Cc: Signed-off-by: Takashi Iwai --- v1->v2: move put_device() before complete() that may free card object for devres-managed case sound/core/init.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/sound/core/init.c b/sound/core/init.c index 2f7f83a7611b..d05bea3c87f5 100644 --- a/sound/core/init.c +++ b/sound/core/init.c @@ -310,7 +310,7 @@ static int snd_card_init(struct snd_card *card, struct = device *parent, kfree(card); /* manually free here, as no destructor called */ return err; } - card->dev =3D parent; + card->dev =3D get_device(parent); card->number =3D idx; WARN_ON(IS_MODULE(CONFIG_SND) && !module); card->module =3D module; @@ -603,6 +603,7 @@ static int snd_card_do_free(struct snd_card *card) dev_warn(card->dev, "unable to free card info\n"); /* Not fatal error */ } + put_device(card->dev); if (card->release_completion) complete(card->release_completion); if (!managed) --=20 2.55.0