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Sun, 20 Sep 2026 23:15:07 -0700 (PDT) Received: from localhost.localdomain ([78.40.184.2]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5b8c78c1398sm1691835e87.7.2026.09.20.23.15.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 20 Sep 2026 23:15:07 -0700 (PDT) From: Roman Demidov To: stable@vger.kernel.org, Greg Kroah-Hartman Cc: Roman Demidov , Jaroslav Kysela , Takashi Iwai , =?UTF-8?q?C=C3=A1ssio=20Gabriel?= , HyeongJun An , bui duc phuc , Kyle Zeng , HanQuan , linux-sound@vger.kernel.org, linux-kernel@vger.kernel.org, lvc-project@linuxtesting.org, Takashi Iwai , Sasha Levin Subject: [PATCH 5.10] ALSA: seq: Clear variable event pointer on read Date: Mon, 21 Sep 2026 09:14:53 +0300 Message-ID: <20260921061454.6421-1-roman.demidov.nn@gmail.com> X-Mailer: git-send-email 2.53.0 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 Content-Type: text/plain; charset="utf-8" From: Kyle Zeng commit 705dd6dcbc0ea87351c660c1a6443f85f1001c76 upstream. snd_seq_read() copies a queued variable-length event header to userspace before expanding the payload. Queued variable-length events use SNDRV_SEQ_EXT_CHAINED internally, and data.ext.ptr points at the first extension cell. The read side strips SNDRV_SEQ_EXT_* bits from data.ext.len before the copy, but it leaves data.ext.ptr untouched. A userspace sequencer client can therefore write a direct variable event to itself and read back the extension-cell kernel address from the returned header. Clear the temporary header pointer before copy_to_user(). The original queued event remains unchanged and is still passed to snd_seq_expand_var_event(), so payload expansion keeps using the internal chain. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Kyle Zeng Link: https://patch.msgid.link/20260607004129.61345-1-kylebot@openai.com Signed-off-by: Takashi Iwai Signed-off-by: Sasha Levin Signed-off-by: Roman Demidov --- Backport fix for CVE-2026-74339 sound/core/seq/seq_clientmgr.c | 1 + 1 file changed, 1 insertion(+) diff --git a/sound/core/seq/seq_clientmgr.c b/sound/core/seq/seq_clientmgr.c index 0363670a56e7..27c8af14a39e 100644 --- a/sound/core/seq/seq_clientmgr.c +++ b/sound/core/seq/seq_clientmgr.c @@ -441,6 +441,7 @@ static ssize_t snd_seq_read(struct file *file, char __u= ser *buf, size_t count, struct snd_seq_event tmpev; tmpev =3D cell->event; tmpev.data.ext.len &=3D ~SNDRV_SEQ_EXT_MASK; + tmpev.data.ext.ptr =3D NULL; if (copy_to_user(buf, &tmpev, sizeof(struct snd_seq_event))) { err =3D -EFAULT; break; --=20 2.53.0