From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5FCC05581EA for ; Tue, 8 Sep 2026 13:43:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788875025; cv=none; b=cZ6gAawTWxWxM3L3awI5tDLPrreKi/gSR83pBe1EHWtuFva4BTYF0maTgHoPVTtFDviBvupyDeWsgd2PXY8eDfO00e1uiuLoLyiEMWXZvNbZ5lR5i9vhYltJ+E83d/UTcVD7Jmplie0KiuVBVM2+mE52voE5RDTI2O+23G/g334= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788875025; c=relaxed/simple; bh=MaQaRisVX7XGOjgkCQF137CpRgZ3WSR6x38EcGC8Bus=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=kub1qh8NmX5zuwBbIi4gyA0w7k/vjoKiGa/fxxHZRBDpMAJhzKNwWw+dXpQN7/oB8O+7H0ARlyqpdGfV8EgD596b/He4uXEsA4ZT33MJj36DstZqeGqzELDRdkQAlaaU0FKKLvB/EV0qZ06a1o4S6m68vD8FjUU0yFMEjf0ldTw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=I6D6Ra7r; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="I6D6Ra7r" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E484C1F00ACF; Tue, 8 Sep 2026 13:43:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788875010; bh=UYK4vD8s9SGVDC4XHAo8r+HxMdrzTAftYHkmVnroOOs=; h=Subject:To:Cc:From:Date; b=I6D6Ra7rkf1dMwb8QZi1XjPpSwslgTq7/gYVbj5/q85rzGUTSTcOKcTzqnZ30kBrM hXP9HYTxYn/cjV68e+3foZtoEjZYC19Yzr0LFhDAGGodlFnL9iLNhZ9SN1w1Q3BCRD bXyj4Umj3o4hn0v8E/3DHe31GcNNhpFpn75wWuLU= Subject: FAILED: patch "[PATCH] misc: fastrpc: don't publish fd before copy_to_user()" failed to apply to 6.18-stable tree To: shoubaineng@gmail.com,christian.koenig@amd.com,sumit.semwal@linaro.org Cc: From: Date: Tue, 08 Sep 2026 15:37:20 +0200 Message-ID: <2026090820-renovator-enjoyable-ee8a@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.18-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y git checkout FETCH_HEAD git cherry-pick -x a4a1a2bfcb29785292d634d7787edc6fb550714d # git commit -s git send-email --to '' --in-reply-to '2026090820-renovator-enjoyable-ee8a@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From a4a1a2bfcb29785292d634d7787edc6fb550714d Mon Sep 17 00:00:00 2001 From: Baineng Shou Date: Mon, 17 Aug 2026 13:04:55 +0800 Subject: [PATCH] misc: fastrpc: don't publish fd before copy_to_user() succeeds MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit fastrpc_ioctl_alloc_dmabuf() calls dma_buf_fd() which installs the fd into the caller's fd table before copy_to_user() copies the fd number back to userspace. If copy_to_user() fails, the fd is already visible to other threads in the same process but the ioctl returns -EFAULT. The existing comment in the code even acknowledges the problem: "The usercopy failed, but we can't do much about it, as dma_buf_fd() already called fd_install()..." Now that dma_buf_fd_install() is available (introduced to fix the same issue in dma-heap), apply the same pattern here: reserve the fd with get_unused_fd_flags(), attempt copy_to_user(), and only on success call dma_buf_fd_install() to publish it atomically with the tracepoint. On copy_to_user() failure, put_unused_fd() and dma_buf_put() cleanly unwind without any user-visible side effects. Fixes: 6cffd79504ce ("misc: fastrpc: Add support for dmabuf exporter") Cc: stable@vger.kernel.org Acked-by: Christian König Acked-by: Sumit Semwal Signed-off-by: Baineng Shou Link: https://lore.kernel.org/r/20260817050457.1005285-3-shoubaineng@gmail.com Signed-off-by: Christian König diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c index eb6c2a78d3c7..d7a9e12f5575 100644 --- a/drivers/misc/fastrpc.c +++ b/drivers/misc/fastrpc.c @@ -1712,24 +1712,20 @@ static int fastrpc_dmabuf_alloc(struct fastrpc_user *fl, char __user *argp) return err; } - bp.fd = dma_buf_fd(buf->dmabuf, O_ACCMODE); + bp.fd = get_unused_fd_flags(O_ACCMODE); if (bp.fd < 0) { dma_buf_put(buf->dmabuf); - return -EINVAL; + return bp.fd; } if (copy_to_user(argp, &bp, sizeof(bp))) { - /* - * The usercopy failed, but we can't do much about it, as - * dma_buf_fd() already called fd_install() and made the - * file descriptor accessible for the current process. It - * might already be closed and dmabuf no longer valid when - * we reach this point. Therefore "leak" the fd and rely on - * the process exit path to do any required cleanup. - */ + put_unused_fd(bp.fd); + dma_buf_put(buf->dmabuf); return -EFAULT; } + dma_buf_fd_install(buf->dmabuf, bp.fd); + return 0; }