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 716524B7A4D; Thu, 17 Sep 2026 15:41:41 +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=1789659712; cv=none; b=uT9KSTKtXCL3KR5sRhZkwJLyQirQGaZ+Gi7vvebD0YQBz84Yh7a0NaooXoiayD8EvqhCIY8oM/3n8f1qDZ05uFivIOGTwvm0MwOnYp3o876lPzOMQvZo8EM/geWcpiqYWfKCyd00sT2A3XDobkSiy3ypfLXSsPtMUFaAvet9d54= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789659712; c=relaxed/simple; bh=+nUZpWf38BR1z1Xq4GYiF8hhDXDOFr2KLt0+0bzfUlo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=tcHeU0ACdBdZ/gdYl7gsaW81p2bhoaCtNU+6Lj8MrxfAcuf4HmZK0dwygQ4KI8oWcicJkGkgKJU9Pa1+GbVsHjDBWcAscSh8YWQa2KWN+QB1gfx322357yequ3mztxPeROTzwMhCSXIdQkhbCKbkcTQ8GcFhERwnKY5qxC0a8HI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=tafA+US8; 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="tafA+US8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 179951F00899; Thu, 17 Sep 2026 15:41:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789659699; bh=tSF2hhzx1YUhP+RIJ7WEBaZwjpAePGh3IhAH6nele0M=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=tafA+US86KreoNjzYTfi3WwjI1DFk2YOEjCqe0mThrnuaYvHSiPlRRKqIQJO9kmlN kfGbc8AM72F7MzDV5H+W6htN6mQXiAc/TOW0ptq7du8CMdthVOitiRHH4ozKm3oFxK kyqr49AmTWf7EtacKaUyJ4vzbL8B9uORn2xOr41k= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Yu Zhang , "Michael S. Tsirkin" , Sasha Levin Subject: [PATCH 7.2 345/733] vhost-vdpa: dont install the eventfd_ctx_fdget() error in config_ctx Date: Thu, 17 Sep 2026 16:10:53 +0100 Message-ID: <20260917151400.157479126@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260917151350.597953846@linuxfoundation.org> References: <20260917151350.597953846@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Yu Zhang [ Upstream commit e74a9fa50749b9940b4fb13199652325e08d3c4a ] vhost_vdpa_set_config_call() swaps the eventfd_ctx_fdget() return value into v->config_ctx before checking it, so on failure the field briefly holds an ERR_PTR: ctx = fd == VHOST_FILE_UNBIND ? NULL : eventfd_ctx_fdget(fd); swap(ctx, v->config_ctx); if (!IS_ERR_OR_NULL(ctx)) eventfd_ctx_put(ctx); if (IS_ERR(v->config_ctx)) { long ret = PTR_ERR(v->config_ctx); v->config_ctx = NULL; return ret; } Commit 0bde59c1723a ("vhost-vdpa: set v->config_ctx to NULL if eventfd_ctx_fdget() fails") added that clearing, and spelled out the invariant the rest of the file relies on: "we consider 'v->config_ctx' valid if it is not NULL". The window between the swap and the clearing still breaks it. vhost_vdpa_config_cb() only tests for NULL, so a config interrupt delivered inside the window hands the ERR_PTR to eventfd_signal(). Check the fd before installing it instead. That closes the window and matches how vhost_vring_ioctl() handles the same failure for the vq call fd. It also stops a rejected fd from tearing down a config interrupt that was working: until now the swap replaced the live context and put it, so after an EBADF the device silently stopped delivering config interrupts until userspace installed a new fd. Fixes: 776f395004d8 ("vhost_vdpa: Support config interrupt in vdpa") Signed-off-by: Yu Zhang Signed-off-by: Michael S. Tsirkin Message-ID: <20260807100025.19750-2-yuz08559@gmail.com> Signed-off-by: Sasha Levin --- drivers/vhost/vdpa.c | 12 ++++-------- 1 file changed, 4 insertions(+), 8 deletions(-) diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c index 4eb1eb5e5c79d..3e5165b7c094e 100644 --- a/drivers/vhost/vdpa.c +++ b/drivers/vhost/vdpa.c @@ -546,18 +546,14 @@ static long vhost_vdpa_set_config_call(struct vhost_vdpa *v, u32 __user *argp) return -EFAULT; ctx = fd == VHOST_FILE_UNBIND ? NULL : eventfd_ctx_fdget(fd); + if (IS_ERR(ctx)) + return PTR_ERR(ctx); + swap(ctx, v->config_ctx); - if (!IS_ERR_OR_NULL(ctx)) + if (ctx) eventfd_ctx_put(ctx); - if (IS_ERR(v->config_ctx)) { - long ret = PTR_ERR(v->config_ctx); - - v->config_ctx = NULL; - return ret; - } - v->vdpa->config->set_config_cb(v->vdpa, &cb); return 0; -- 2.53.0