From: Šerif Rami Date: Tue, 19 Aug 2025 18:51:33 +0000 (+0200) Subject: ALSA: usb-audio: us144mkii: Fix null-deref in tascam_midi_in_urb_complete() X-Git-Tag: v6.18-rc1~135^2~233 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=0c5e2ae204eca74e4ccbaffc8125c3b41de9c9b8;p=thirdparty%2Flinux.git ALSA: usb-audio: us144mkii: Fix null-deref in tascam_midi_in_urb_complete() 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. Fixes: 67afec157fe6 ("ALSA: usb-audio: us144mkii: Add MIDI support and mixer controls") Reported-by: Dan Carpenter Closes: https://lore.kernel.org/r/202508192109.lcMrINK1-lkp@intel.com/ Signed-off-by: Šerif Rami Link: https://patch.msgid.link/20250819185133.10464-1-ramiserifpersia@gmail.com Signed-off-by: Takashi Iwai --- diff --git a/sound/usb/usx2y/us144mkii_midi.c b/sound/usb/usx2y/us144mkii_midi.c index 5759f601007f8..08b04aa392781 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 = urb->context; int ret; + if (!tascam) + goto out; + if (urb->status) { if (urb->status != -ENOENT && urb->status != -ECONNRESET && urb->status != -ESHUTDOWN && urb->status != -EPROTO) { @@ -51,7 +54,7 @@ void tascam_midi_in_urb_complete(struct urb *urb) goto out; } - 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); @@ -65,8 +68,9 @@ void tascam_midi_in_urb_complete(struct urb *urb) dev_err(tascam->card->dev, "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); }