From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ot1-f48.google.com (mail-ot1-f48.google.com [209.85.210.48]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1D2FF40DFC7 for ; Wed, 27 May 2026 16:06:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.48 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779898011; cv=none; b=b6p8B6BnBPngkuJ9gqu2kOKc7fo+K2J4fEwNlPul9KoZ3yDoClwZChoFZBV98vI+NBr1VGe095e7IG43s4jbEXY/GtQgk62fFkkOjNshS0D5baHp3eGzB9/SKtgduPVlcWokh18UyPjphN/mMZcU0jSLe82BrZ/V7kIyVJaelOo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779898011; c=relaxed/simple; bh=fwkxSqx7ty2JQSbgYGjXCJheNp4aXVJfNCMAJtiBUtE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=XnoWxVLdMLicCBhbiCyyJQ+hJ0Ie3EmBDwD7cFmhB6D4Q2xOLzouvxRgOlyOFIz5eSLGWTettd/26wOU5Z5SKy9NsmL5FmSvAeuVtn2VIbzQk/CqhbOa18Z8GDxFhGjn9C8jv0syLTAKhv1erujTz8spaAXVvsG94OutI2r8/hw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.dk; spf=pass smtp.mailfrom=kernel.dk; dkim=pass (2048-bit key) header.d=kernel-dk.20251104.gappssmtp.com header.i=@kernel-dk.20251104.gappssmtp.com header.b=O1aMiL1o; arc=none smtp.client-ip=209.85.210.48 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.dk Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=kernel.dk Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20251104.gappssmtp.com header.i=@kernel-dk.20251104.gappssmtp.com header.b="O1aMiL1o" Received: by mail-ot1-f48.google.com with SMTP id 46e09a7af769-7de431da8fbso9862932a34.1 for ; Wed, 27 May 2026 09:06:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20251104.gappssmtp.com; s=20251104; t=1779898008; x=1780502808; darn=vger.kernel.org; h=content-transfer-encoding:in-reply-to:from:content-language :references:cc:to:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=DDewevQlsNX9Nf5an4WdPkqFyUO5oYIAKU8piRx5pII=; b=O1aMiL1oIFen2XoIfw6SCJALa8Ot1OyXMqMDB/oU7qEd7xqcpJcmD2Obpa7Xhf18Wb Tv/hwDlI7f60fJZz3LA5WSK4ha8sHBqy0Kfvy69FTonSDHkqHImBe3jY7r5kUGVV69g6 DhgWZzngjuvHdU+DNARaOlOBOOyKC+yJ6iCMDZXnpaxkUD82iSBKl0+T6BjDJfWzZiQg 6B27azfpAuiutURWisO1EMMtvonRee30OHl5YFyTxvXi+wBdj4rE79r/FP+yG15cxFY8 kseLG06/4whit0X1Jj2asavVTSHHe2CqrCILfrcIu8BMz8zsF0kxznceQwGoyP4Yuqbv 9JUA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1779898008; x=1780502808; h=content-transfer-encoding:in-reply-to:from:content-language :references:cc:to:subject:user-agent:mime-version:date:message-id :x-gm-gg:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=DDewevQlsNX9Nf5an4WdPkqFyUO5oYIAKU8piRx5pII=; b=Ey+e8ed/7VPkIATJSnj6Qd1p5lfbJ/maeijhw+SBh5+yGHpI9bI74aOJfnjSbjVh07 ZnmJKrs5W9a4ujvn5u46yCunCQbW90hYx+4clr2LBjqmJH4HLtblCG2zsxJXviJwYdLh XF17F2Clv84RyR2XnvpUNCUHlETuNfkjYs4UGM7YqOmxoQvNgAHpvOxWixmOfkM+coqf 6o+4RShlJ3sPSNp4rrEBdsMJmqCQlxcFRXBIdkRCzX8/18pISXZp61dBI+LN7RNnwnRz GLuOfkz8fKC1MaUUFoFjQmkxKbbCDPsOD7DCbXIJ0SJR4efc0gE3CEKHKRl70cbzNMI7 nl1w== X-Forwarded-Encrypted: i=1; AFNElJ/JxLXg+Y0uyeNNqpHodHYCgWGoHCiXKWp7PAYpyuZdsT85v6+llD6oprZOp8djWrDYUhb1oSP166Dr0oU=@vger.kernel.org X-Gm-Message-State: AOJu0YyzRK57/6zpSCfeAIoouMIfUX41hQgTcJdZx9ID3JSBMQF9Nx61 K6sZ68IMZOcWuGl+RpxaF8tzQ5/u7iwt2VnxKEVCMUiGmjbz6Wb4MhcXjePNkURTLJ0= X-Gm-Gg: Acq92OENrk7ywUtsU1+18nAUF5RoPtZHUTBxZctwv0TfTCWDT+x2R3kilsRYOEoH04A zF/yf56YtxexvVUpVcDOZjq5eJGymxDcpxOePOiQI3bDxWibipL90FyX6ClX3UMGV3XPK2LD3Aq Dk1TZ90rW9IhxBwtbJXg5vNPJES/NvX6EEInFm3uaLAiQYxg2MFo/DVMqWxg+np+iDQiZHkXETB ndFSE0h7CCbnfxiGC8dFrpFN7r3uJ7+KS1jlC7lhUu2CogStjiR6WgRo16o6DuWb4XPrfiXjWNl swWwJ2e7en1T8JpWNuiIs6eJu7cUkpGUnGndKeP9DsHFtK+rhz4ZdXdhYrg311V6kxu5nfBJ/ky Q+Wt/KZuSEqwMzuZB2TCoWTjKB7phoGEN1m2ClEyE+gwpiM3XJzDGbeEVFiRTTVKb7gB8chaIhi GKqS9z0MkYxK4MQ6F95K7UdGRB3aiSaGZKxeUsj0b5mAchDX+PNl7EcbugPla/yRMek+JnP4C+6 bA9c1Zitml7Q/UJU8A= X-Received: by 2002:a05:6830:6682:b0:7dc:dd58:50a1 with SMTP id 46e09a7af769-7e5fee5ef73mr15600883a34.15.1779898007969; Wed, 27 May 2026 09:06:47 -0700 (PDT) Received: from [192.168.1.102] ([96.43.243.2]) by smtp.gmail.com with ESMTPSA id 46e09a7af769-7e606459bf7sm11606383a34.1.2026.05.27.09.06.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 27 May 2026 09:06:45 -0700 (PDT) Message-ID: Date: Wed, 27 May 2026 10:06:44 -0600 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] scsi: bsg: copy uring_cmd payload to prevent double-fetch from shared SQE To: Rahul Chandelkar , "James E . J . Bottomley" , "Martin K . Petersen" , FUJITA Tomonori Cc: linux-scsi@vger.kernel.org, linux-block@vger.kernel.org, io-uring@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20260527105931.3950913-1-rc@rexion.ai> Content-Language: en-US From: Jens Axboe In-Reply-To: <20260527105931.3950913-1-rc@rexion.ai> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 5/27/26 4:59 AM, Rahul Chandelkar wrote: > scsi_bsg_uring_cmd() and scsi_bsg_map_user_buffer() read bsg_uring_cmd > fields directly from the shared mmap'd io_uring submission ring via > io_uring_sqe128_cmd(). On the inline execution path, io_uring has not > yet copied the SQE to kernel memory, so a concurrent userspace thread > can modify fields between reads. > > cmd->request_len is read for the bounds check, for the cmd_len > assignment, and for the copy_from_user length. A racing thread can > change request_len between the bounds check (passes with <= 32) and > copy_from_user (uses the enlarged value), overflowing the 32-byte > scmd->cmnd[] buffer into subsequent struct scsi_cmnd fields. > > scsi_bsg_map_user_buffer() independently re-derives its cmd pointer > from the same shared SQE, re-reading dout_xfer_len, din_xfer_len, > dout_xferp, and din_xferp, enabling direction confusion and buffer > length races. > > Copy struct bsg_uring_cmd to a stack-local variable before use in both > functions. The pointer variable 'cmd' is redirected to the local copy > so the rest of each function is unchanged. > > Tested with KASAN on QEMU (virtio-scsi, 2 vCPUs). Without this fix, > a two-thread race produces: > > BUG: KASAN: wild-memory-access in scsi_queue_rq+0x4a3/0x58a0 > Write of size 96 at addr dead000000001000 by task poc/67 > Call Trace: > kasan_report+0xce/0x100 > __asan_memset+0x23/0x50 > scsi_queue_rq+0x4a3/0x58a0 > scsi_bsg_uring_cmd+0x942/0x1570 > io_uring_cmd+0x2f6/0x950 > io_issue_sqe+0xe5/0x22d0 I don't think this is the right way to fix it, ->sqe should've been stable upfront if this ends up happening. Can you share your poc with me? Your trace has been trimmed down way too much to be useful. -- Jens Axboe