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[93.87.121.239]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-afded52ea4asm19026566b.101.2025.08.19.10.39.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 19 Aug 2025 10:39:10 -0700 (PDT) From: =?UTF-8?q?=C5=A0erif=20Rami?= To: Jaroslav Kysela , Takashi Iwai , Stephen Rothwell , =?UTF-8?q?=C5=A0erif=20Rami?= , linux-sound@vger.kernel.org (open list:SOUND), linux-kernel@vger.kernel.org (open list) Cc: kernel test robot , Dan Carpenter Subject: [PATCH] ALSA: usb-audio: us144mkii: Fix null-deref in tascam_midi_in_urb_complete() Date: Tue, 19 Aug 2025 19:38:30 +0200 Message-ID: <20250819173831.30818-1-ramiserifpersia@gmail.com> X-Mailer: git-send-email 2.50.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable The smatch tool reported a potential null pointer dereference in tascam_midi_in_urb_complete(). The 'tascam' variable, derived from 'urb->context', was checked for nullity in one place, but dereferenced without a check in several other places. This patch fixes the issue by adding a null check at the beginning of the function. If 'tascam' is null, the function now safely exits. This prevents any potential crashes from null pointer dereferences. It also fixes a latent bug where 'usb_put_urb()' could be called twice for the same URB on submission failure, which would lead to a use-after-free error. Reported-by: kernel test robot Reported-by: Dan Carpenter Closes: https://lore.kernel.org/r/202508192109.lcMrINK1-lkp@intel.com/ Signed-off-by: =C5=A0erif Rami --- sound/usb/usx2y/us144mkii_midi.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/sound/usb/usx2y/us144mkii_midi.c b/sound/usb/usx2y/us144mkii_m= idi.c index 5759f6010..1aca38f38 100644 --- a/sound/usb/usx2y/us144mkii_midi.c +++ b/sound/usb/usx2y/us144mkii_midi.c @@ -41,6 +41,9 @@ void tascam_midi_in_urb_complete(struct urb *urb) struct tascam_card *tascam =3D urb->context; int ret; =20 + if (!tascam) + goto out; + if (urb->status) { if (urb->status !=3D -ENOENT && urb->status !=3D -ECONNRESET && urb->status !=3D -ESHUTDOWN && urb->status !=3D -EPROTO) { @@ -51,7 +54,7 @@ void tascam_midi_in_urb_complete(struct urb *urb) goto out; } =20 - if (tascam && atomic_read(&tascam->midi_in_active) && + if (atomic_read(&tascam->midi_in_active) && urb->actual_length > 0) { kfifo_in_spinlocked(&tascam->midi_in_fifo, urb->transfer_buffer, urb->actual_length, &tascam->midi_in_lock); @@ -66,11 +69,14 @@ void tascam_midi_in_urb_complete(struct urb *urb) "Failed to resubmit MIDI IN URB: error %d\n", ret); usb_unanchor_urb(urb); usb_put_urb(urb); + goto out; } + out: usb_put_urb(urb); } =20 + /** * tascam_midi_in_open() - Opens the MIDI input substream. * @substream: The ALSA rawmidi substream to open. --=20 2.50.1