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=1794408323; b=kGncBU3EJjLMIgb6zESzC20RzAo0isMOOvqiy/tqlpDr9T6Wldy09ADvAbpASbv1HBrS l67IKM2QEXW3D96Vvv+Ndbv9slSWNlYfH5NvvnQzWU0yuQg8dLWy89AtiiBjo/1QdyCE7 Dy2DM+gaUmzh4UqjuU6RqINoD8FMhyseDvxJJiNtSvvFTdOsZRBEayLu4Sg93JphlFxYm Hz/4WX5HpQDbpnzuwzkTYYcTHKIO8ktktFqmJ47K0+phI8ivizChGQhkomL1IPMiMhDx1 zQG59/NEC/mCweFA6QjJn+i3Sk9rMaOXK/n57pGvV42HDgk5EuLgtgE7eaYWN2cmymg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794408323; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=rTiVOnY8HgSOulFoi0YIAWmyA8fU+hSpntGW97c/Kqs=; b=JgsDauhZR7W91y2n/7qqSG3TzQdIzdlvhAH80JQ64Pvk3FN44O7wlPRdCU/5vMyy6u1p x1sUv88QryChSKT61XYPccqk6+qmfbP26hiEFE3y6Pq7Sc6SV6h4Tg4OA03GreZvVClDz hk33br8U1TDhTPRlr/7muGyNw+tGJ8E5grrl3qdoUL9AQxa5CT1iICm55raCwpXDA1NuF uVJ3Fu9TmBnMIHpbiAgOnHmCHlcuF0Ycu7WAQYJf0K2ByWHFqPED1BOxDFD0VHfPcWKWW VDfzWorHgEIpqMrL+Fng50F1Bxi32ID7n12fvpDIR2YmID2G7xoP5aExzRdzmE2/thA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=GBsh7RbD; 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 13C18606A334 for ; Wed, 11 Nov 2026 14:45:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=GBsh7RbD Received: by smtp.kernel.org (Postfix) with ESMTPSA id 561F71F00A05; Wed, 11 Nov 2026 14:45:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794408322; bh=rTiVOnY8HgSOulFoi0YIAWmyA8fU+hSpntGW97c/Kqs=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=GBsh7RbDQiUBZDZNFkvY/spbc5G7MWICrsoWvwfUd/xu01qIynL1KsNfCq3/ZhCXw rSb3+iNS+KG8LTu0/+ThhIlNexy+8YNQxGvlsjM3D26r1WrAw0hQIeBdeMLc5xNSrw E73ingNdaBEsarpb0qvAeOuCy3umBPqtdS1pw6hmb+U4j98ZpjmsUfzU+7n3WwvTEo noos7J9y/FMOhcfY5bwj8/ELqsGn0ZVDiTpbbK7O90PDaOMN4BAAzOXUlgiki6Fa5I KiRG9b3yQWyUpn9L97mOzLZGkKzuhX7MvxmoA4tx6WnYD6+25HAWTBhi54laufxPg5 eQ/wwoZyWnhOw== From: Sasha Levin To: stable@vger.kernel.org Cc: Dominik Maier , Jens Axboe , Sasha Levin Subject: [PATCH 5.10.y] loop: check for read-write open mode on LOOP_SET_STATUS in lo_compat_ioctl() Date: Wed, 11 Nov 2026 09:45:20 -0500 Message-ID: <20261111143400.1667764-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261107062925-failed-5.10-87409eedc543@kernel.org> References: <20261107062925-failed-5.10-87409eedc543@kernel.org> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Dominik Maier [ Upstream commit 87409eedc543d288cdd49c2174f7d61eca7b8db5 ] lo_ioctl() checks for (mode & BLK_OPEN_WRITE) || capable(CAP_SYS_ADMIN) before allowing LOOP_SET_STATUS or LOOP_SET_STATUS64, but not lo_compat_ioctl(), the handler used by 32-bit user space on 64-bit kernels. As a result, on 64-bit kernels with CONFIG_COMPAT=y, a 32-bit unprivileged user-space process holding a read-only (O_RDONLY) file descriptor to an active /dev/loopN device can issue a compat LOOP_SET_STATUS ioctl to modify lo_offset, clear lo_sizelimit to 0 (exposing backing-file data past the configured limit), or alter lo_flags. Enforce the same (mode & BLK_OPEN_WRITE) || capable(CAP_SYS_ADMIN) check on LOOP_SET_STATUS in lo_compat_ioctl(). Cc: stable@vger.kernel.org Assisted-by: ARTIST LLM Signed-off-by: Dominik Maier Reviewed-by: Bart Van Assche bvanassche@acm.org Link: https://patch.msgid.link/20261025200740.2064379-1-dmnk@google.com Signed-off-by: Jens Axboe [ sashal: Replaced BLK_OPEN_WRITE with FMODE_WRITE to match the existing fmode_t interface. ] Signed-off-by: Sasha Levin --- drivers/block/loop.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/block/loop.c b/drivers/block/loop.c index dab31049bd4fa..a25467bb1cc74 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -1850,8 +1850,10 @@ static int lo_compat_ioctl(struct block_device *bdev, fmode_t mode, switch(cmd) { case LOOP_SET_STATUS: - err = loop_set_status_compat(lo, - (const struct compat_loop_info __user *)arg); + err = -EPERM; + if ((mode & FMODE_WRITE) || capable(CAP_SYS_ADMIN)) + err = loop_set_status_compat(lo, + (const struct compat_loop_info __user *)arg); break; case LOOP_GET_STATUS: err = loop_get_status_compat(lo, -- 2.53.0