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Fri, 12 Jun 2026 07:53:22 +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 +sQPOvK6K2qrIwAAD6G6ig (envelope-from ); Fri, 12 Jun 2026 07:53:22 +0000 Date: Fri, 12 Jun 2026 09:53:22 +0200 Message-ID: <87y0gki499.wl-tiwai@suse.de> From: Takashi Iwai To: WenTao Liang Cc: perex@perex.cz, tiwai@suse.com, chenziqing@xiaomi.com, broonie@kernel.org, cezary.rojewski@intel.com, kees@kernel.org, linux-sound@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] sound/core: fix refcount leak in snd_ctl_elem_info_user() In-Reply-To: <20260612022121.14329-1-vulab@iscas.ac.cn> References: <20260612022121.14329-1-vulab@iscas.ac.cn> User-Agent: Wanderlust/2.15.9 (Almost Unreal) Emacs/30.2 Mule/6.0 Precedence: bulk X-Mailing-List: linux-sound@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-Spam-Flag: NO X-Rspamd-Action: no action X-Spam-Level: X-Spamd-Result: default: False [-3.51 / 50.00]; BAYES_HAM(-3.00)[100.00%]; MID_CONTAINS_FROM(1.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; 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)[]; FUZZY_RATELIMITED(0.00)[rspamd.com]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; TO_DN_SOME(0.00)[]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; RCVD_TLS_ALL(0.00)[]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_SEVEN(0.00)[10]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,imap1.dmz-prg2.suse.org:rdns,suse.de:mid,suse.de:dkim]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; DKIM_TRACE(0.00)[suse.de:+] X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Rspamd-Queue-Id: 4BA1575C2A X-Spam-Score: -3.51 On Fri, 12 Jun 2026 04:21:21 +0200, WenTao Liang wrote: > > snd_ctl_elem_info_user() calls snd_power_ref_and_wait() to obtain > a power reference for the sound card. If that function returns an > error (e.g. -ENODEV when the card is shutting down), the reference > is still held because snd_power_ref_and_wait() always acquires it > unconditionally. However, the error path in snd_ctl_elem_info_user() > directly returns the error without releasing the reference, causing > a refcount leak. > > Fix it by calling snd_power_unref() before returning the error, > matching the successful path that already does the paired unref. > > Cc: stable@vger.kernel.org > Fixes: fcc62b19104a ("ALSA: control: Take power_ref lock primarily") > Signed-off-by: WenTao Liang Judging from the current code patterns, it's better to fix the function behavior itself -- unreference in snd_power_ref_and_wait() itself when returning an error; otherwise there are way too many callers to fix up, and the current behavior is rather confusing. Could you try the patch below instead? thanks, Takashi -- 8< -- --- a/sound/core/init.c +++ b/sound/core/init.c @@ -1139,7 +1139,7 @@ EXPORT_SYMBOL(snd_card_file_remove); * typically around calling control ops. * * The caller needs to pull down the refcount via snd_power_unref() later - * no matter whether the error is returned from this function or not. + * when this function returns 0. * * Return: Zero if successful, or a negative error code. */ @@ -1152,7 +1152,11 @@ int snd_power_ref_and_wait(struct snd_card *card) card->shutdown || snd_power_get_state(card) == SNDRV_CTL_POWER_D0, snd_power_unref(card), snd_power_ref(card)); - return card->shutdown ? -ENODEV : 0; + if (card->shutdown) { + snd_power_unref(card); + return -ENODEV; + } + return 0; } EXPORT_SYMBOL_GPL(snd_power_ref_and_wait); @@ -1169,7 +1173,8 @@ int snd_power_wait(struct snd_card *card) int ret; ret = snd_power_ref_and_wait(card); - snd_power_unref(card); + if (!ret) + snd_power_unref(card); return ret; } EXPORT_SYMBOL(snd_power_wait);