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 C0E2849BD6C for ; Thu, 10 Sep 2026 15:52:37 +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=1789055559; cv=none; b=KmmCX/iHZuMu7pneHp5u4aacitzOJZmKWuSPvoUkvJj1AmkA90TrYqKfywH7j0Mv8tkFeMkzZ3x/IIAhzF4FKZ1jZfDFj/COpWqWwBnRB6SbVNFFoz8FPulPtGHt0UbOnCFO440OjE6T9YiAJHicEPy3UfSAm8G78dkQpoYWPVo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789055559; c=relaxed/simple; bh=XmwJ8V/1mz+8kPYvCf8GcjNmYAeOgK5HrwVVT5cJ4jQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=TjRYNp7wdvE/syI90XnM2Tbgi9gggN8M9TcmM3sYEP1zmrOWUVRLQOkyGr5WwEIlA66AQlJTszutuuWA/3+k+lrcd6l3qy/I75kf9QATWnQfbR+AHDiMYr3Yh81XQiTIuXjeVcOizjJ0wskKoVETqpFg5TvhoE+K6vpfqMfbVAA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=aZywIRen; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="aZywIRen" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B526D1F00898; Thu, 10 Sep 2026 15:52:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789055557; bh=2qOBAmSwWIrCRrcWnsu8mRo+VK7KOUckKIz7g6Eq4E8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=aZywIRendJXdIn4ayQQvJfIegOZu986+J8YQRIH/ivX9qcG8ahjNfZ6MmxgzbccJv nbyS/a9X/PSkiYtChENObH6mIIeacW4QCYPnQbZjm0BKIYkVFK03ONuVjmYNev28+G VSgDsbbjmfYAzhdcTAqaGf1/ICDlH3DUyF4CRcCGCYteaTPuyuRnjsuFFiVHB3qJaX cYwxdI2lqQPkQDCRSS1dPLvQcCfGau1X+KCRJRxt+kJWGnIQJlmtKbPWtkJvhrgnGq YttkqPVO9vPh95fPrLuZ2/2/0zzBhz0V9eETcJc/Hg7ac0r8PjKGjHOmY7zOhl6EnO tyNrrLPYJ2gcQ== From: Sasha Levin To: stable@vger.kernel.org Cc: Baineng Shou , =?UTF-8?q?Christian=20K=C3=B6nig?= , Sumit Semwal , Sasha Levin Subject: [PATCH 6.18.y 2/2] misc: fastrpc: don't publish fd before copy_to_user() succeeds Date: Thu, 10 Sep 2026 11:52:34 -0400 Message-ID: <20260910155234.1080006-2-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260910155234.1080006-1-sashal@kernel.org> References: <2026090820-renovator-enjoyable-ee8a@gregkh> <20260910155234.1080006-1-sashal@kernel.org> 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 From: Baineng Shou [ Upstream commit a4a1a2bfcb29785292d634d7787edc6fb550714d ] 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 Signed-off-by: Sasha Levin --- drivers/misc/fastrpc.c | 16 ++++++---------- 1 file changed, 6 insertions(+), 10 deletions(-) diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c index e240b94644809..29f9003999a07 100644 --- a/drivers/misc/fastrpc.c +++ b/drivers/misc/fastrpc.c @@ -1681,24 +1681,20 @@ 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; } -- 2.53.0