From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793831640; b=PFKN2s+mW/NyZPUqVyo5LEQmWdGWNeBHKMyCTiprxTcKW1hblmPkV9/OCzM66s6aWhGz MgykNWIRKYoPX4H1avC175gnreHTyUNblBCcuE+nB71usHFwxTsA2sn4lCOzfD8JsvIOq wBaADmmuXfMWnBS3jgp+5sJcYda02XcJunHamM5Ctj1juwErgLVyalQApOgXtEHFFdooY RMT7y6oqEEUCKYiww56frzgrmolLjbg6r7XNrX9w6wgmdgWoxJWdWXvCbZLuxT3KeYXOE pCmkPWnugnl8d8ECiq6IeziiSSG2GpQe+Zq+ZV8a6Gn48Djz8211voAzR12HQPisAlQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793831640; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=x7NsFW++CaIcuSO8oCPGi//28Sueru9w6y7Nb+qSNT0=; b=YRjqhRAu5fiMBRF8Lydhaa5b11Be/l+4vT1Dw1d4lqZ80E9dKUIh25cjCUbmTWI5/1c1 BoYAjnayM02SVsCqEH0vySV1pzsAhbU8LQQoWyds0qlPWJ4qlrVKpwh7Gmf5wUY5FOfPs ioiN0HZccY2hAQeosM/l7bLZkpXOPV6aQ+bjFOX7R+SJC98CZ2LUNw9WvO3nuL+oNGjEy ekPbjdDXlcw8ZeFW5FxZ2zAcuUsFKxW5Uxmsk2y1CZ/tTDxTWd328rA4FPWwEBnzGltDI SCQ0/pR0pFZGz9zcO1vrKAIQbxOyhYQbnTQjOUutLY9seV9ygOldaIDkEQsp4FZTjkw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=SiKCUrGM; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F40B1606B2C6; Wed, 4 Nov 2026 22:33:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=SiKCUrGM Received: by smtp.kernel.org (Postfix) with ESMTPSA id 904D01F000C1; Wed, 4 Nov 2026 22:33:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793831639; bh=x7NsFW++CaIcuSO8oCPGi//28Sueru9w6y7Nb+qSNT0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=SiKCUrGMs93xur5LC8Uh9frc0lVyw8M4ecry/PE9qjMAteI5d8jjx9iNEXNn2W3n9 gEBRdk5qFdaC5fA+0GyYACBbcHsD7EvVoJLcuy5HbppYDgKA7I+73bD0PKewGtJNsT MiRQt2o5NMmHdcEICIngofxVX5j6KvUwYm583ck8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+37a57a84893052ab6071@syzkaller.appspotmail.com, Aleksandr Nogikh , Hans Verkuil , Sasha Levin Subject: [PATCH 6.18 0826/1005] media: usbtv: fix null-pointer dereference on disconnect Date: Wed, 4 Nov 2026 16:09:19 -0500 Message-ID: <20261104211106.473201352@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261104211043.516122098@linuxfoundation.org> References: <20261104211043.516122098@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Aleksandr Nogikh [ Upstream commit cb705f75d03e946a4514488beb9e3bac9bcdb2e6 ] A null-pointer dereference can occur in usb_make_path() when called from usbtv_querycap() (and other ioctl handlers) during device disconnection. Oops: general protection fault, probably for non-canonical address 0xdffffc000000000a: 0000 [#1] SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000050-0x0000000000000057] RIP: 0010:usb_make_path include/linux/usb.h:985 [inline] RIP: 0010:usbtv_querycap+0x9c/0x100 drivers/media/usb/usbtv/usbtv-video.c:612 ... Call Trace: v4l_querycap+0x236/0x470 drivers/media/v4l2-core/v4l2-ioctl.c:1106 __video_do_ioctl+0x8af/0xc70 drivers/media/v4l2-core/v4l2-ioctl.c:3133 video_usercopy+0x860/0x1430 drivers/media/v4l2-core/v4l2-ioctl.c:3475 v4l2_ioctl+0x18d/0x1e0 drivers/media/v4l2-core/v4l2-dev.c:366 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94 This happens due to a race condition between the USB device disconnect routine (usbtv_disconnect()) and V4L2 ioctls. When the device is disconnected, usbtv_disconnect() sets usbtv->udev = NULL without holding the usbtv->v4l2_lock mutex. Concurrently, an ioctl handler like usbtv_querycap() can be executing under the v4l2_lock and attempt to use usbtv->udev, leading to a crash. To fix this, move the usbtv->udev = NULL assignment into usbtv_video_free() and protect it with mutex_lock(&usbtv->v4l2_lock). This ensures that no non-queue ioctl handler can run concurrently with the pointer being nullified. If an ioctl is already running, the mutex will block the disconnect path until the ioctl finishes. If an ioctl is blocked waiting for the lock, it will acquire it after the disconnect routine releases it, but will then check video_is_registered() (which was cleared by vb2_video_unregister_device()) and safely return -ENODEV. Acquiring v4l2_lock after vb2_video_unregister_device() avoids reintroducing a historical deadlock issue, and usbtv_audio_free() remains safe as it is called before usbtv_video_free(). Fixes: 65e6a2773d65 ("media: usbtv: Remove useless locks in usbtv_video_free()") Cc: stable@vger.kernel.org Assisted-by: Gemini:gemini-3.6-flash Gemini:gemini-3.1-pro-preview syzbot Reported-by: syzbot+37a57a84893052ab6071@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=37a57a84893052ab6071 Link: https://syzkaller.appspot.com/ai_job?id=5abbe65a-5853-4bc2-9135-5c75f88d51ed Signed-off-by: Aleksandr Nogikh Signed-off-by: Hans Verkuil Signed-off-by: Sasha Levin --- drivers/media/usb/usbtv/usbtv-core.c | 2 -- drivers/media/usb/usbtv/usbtv-video.c | 4 ++++ 2 files changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/media/usb/usbtv/usbtv-core.c b/drivers/media/usb/usbtv/usbtv-core.c index 4925113af9603..a444ef56b4668 100644 --- a/drivers/media/usb/usbtv/usbtv-core.c +++ b/drivers/media/usb/usbtv/usbtv-core.c @@ -136,8 +136,6 @@ static void usbtv_disconnect(struct usb_interface *intf) usbtv_audio_free(usbtv); usbtv_video_free(usbtv); - usbtv->udev = NULL; - /* the usbtv structure will be deallocated when v4l2 will be done using it */ v4l2_device_put(&usbtv->v4l2_dev); diff --git a/drivers/media/usb/usbtv/usbtv-video.c b/drivers/media/usb/usbtv/usbtv-video.c index de0328100a60d..ef066df712469 100644 --- a/drivers/media/usb/usbtv/usbtv-video.c +++ b/drivers/media/usb/usbtv/usbtv-video.c @@ -968,5 +968,9 @@ void usbtv_video_free(struct usbtv *usbtv) vb2_video_unregister_device(&usbtv->vdev); v4l2_device_disconnect(&usbtv->v4l2_dev); + mutex_lock(&usbtv->v4l2_lock); + usbtv->udev = NULL; + mutex_unlock(&usbtv->v4l2_lock); + v4l2_device_put(&usbtv->v4l2_dev); } -- 2.53.0