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Tue, 13 Oct 2026 12:05:36 +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 6Ox+GJAezmrxFQAAD6G6ig:T4 (envelope-from ); Tue, 13 Oct 2026 12:05:36 +0000 From: Takashi Iwai To: linux-sound@vger.kernel.org Cc: linux-kernel@vger.kernel.org Subject: [PATCH 3/4] ALSA: pcm: Protect delay DMA sync in forward and rewind, too Date: Tue, 13 Oct 2026 14:05:24 +0200 Message-ID: <20261013120528.52586-4-tiwai@suse.de> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20261013120528.52586-1-tiwai@suse.de> References: <20261013120528.52586-1-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-Rspamd-Action: no action X-Spam-Score: -3.01 X-Spam-Flag: NO 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)[]; DNSWL_BLOCKED(0.00)[2a07:de40:b281:104:10:150:64:97:from]; MIME_TRACE(0.00)[0:+]; RCVD_VIA_SMTP_AUTH(0.00)[]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; ARC_NA(0.00)[]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; DWL_DNSWL_BLOCKED(0.00)[suse.de:dkim]; RCPT_COUNT_TWO(0.00)[2]; RCVD_TLS_ALL(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:email,suse.de:dkim,imap1.dmz-prg2.suse.org:helo,imap1.dmz-prg2.suse.org:rdns]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; TO_DN_NONE(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; DKIM_TRACE(0.00)[suse.de:+] X-Spam-Level: X-Rspamd-Queue-Id: 4735421F3B X-Rspamd-Server: rspamd2.dmz-prg2.suse.org Like the previous fix for snd_pcm_delay() (in the commit 50f413b83b31 "ALSA: pcm: Protect delay DMA sync against concurrent HW_FREE"), the snd_pcm_dma_buffer_sync() call in snd_pcm_forward() and snd_pcm_rewind() needs the similar protection against the concurrent hw_free action for avoiding potential UAFs. Fixes: a25684a95646 ("ALSA: memalloc: Support for non-contiguous page allocation") Reported-by: Sashiko Signed-off-by: Takashi Iwai --- sound/core/pcm_native.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c index f774358629bb..c1bad92a4e9f 100644 --- a/sound/core/pcm_native.c +++ b/sound/core/pcm_native.c @@ -3078,11 +3078,15 @@ static snd_pcm_sframes_t rewind_appl_ptr(struct snd_pcm_substream *substream, static snd_pcm_sframes_t snd_pcm_rewind(struct snd_pcm_substream *substream, snd_pcm_uframes_t frames) { + struct snd_pcm_runtime *runtime = substream->runtime; snd_pcm_sframes_t ret; if (frames == 0) return 0; + /* Keep the DMA buffer alive through the sync below. */ + if (!atomic_inc_unless_negative(&runtime->buffer_accessing)) + return -EBUSY; scoped_guard(pcm_stream_lock_irq, substream) { ret = do_pcm_hwsync(substream); if (!ret) @@ -3091,17 +3095,22 @@ static snd_pcm_sframes_t snd_pcm_rewind(struct snd_pcm_substream *substream, } if (ret >= 0) snd_pcm_dma_buffer_sync(substream, SNDRV_DMA_SYNC_DEVICE); + atomic_dec(&runtime->buffer_accessing); return ret; } static snd_pcm_sframes_t snd_pcm_forward(struct snd_pcm_substream *substream, snd_pcm_uframes_t frames) { + struct snd_pcm_runtime *runtime = substream->runtime; snd_pcm_sframes_t ret; if (frames == 0) return 0; + /* Keep the DMA buffer alive through the sync below. */ + if (!atomic_inc_unless_negative(&runtime->buffer_accessing)) + return -EBUSY; scoped_guard(pcm_stream_lock_irq, substream) { ret = do_pcm_hwsync(substream); if (!ret) @@ -3110,6 +3119,7 @@ static snd_pcm_sframes_t snd_pcm_forward(struct snd_pcm_substream *substream, } if (ret >= 0) snd_pcm_dma_buffer_sync(substream, SNDRV_DMA_SYNC_DEVICE); + atomic_dec(&runtime->buffer_accessing); return ret; } -- 2.55.0