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=1794063691; b=SVEdhPN1BYjN07bRd+1UwHtHS+iioX+1h6Phi0O4Ry2d6oVR2vXhlbo9NNkM5quyzUP+ jQU3xOIaek+VwQxwmAGBpi39laXf4yIQN+Mv5zVMS/psAzQEiF+RJ+7PTglU/IxDlIXuC VONDorB7kF83CIthkfIWmBdmuQ/porzx/IV4O434UGtN18AEh99SyapKCn8A7RrMF6kt1 wRVXyNeSPOo5//k198sPltfTxEy5UDXd8iksCJJOmz3rvP4vxisitYBOGZvgmmSzninpp C0tMVk85Amt+9A1jbEHvdETqc1eiAD8hUBeR1/L0nO0YMUDBQYjWf923QcDEMCDsINA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794063691; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=eeA49f8JeRLRTGiOktfxjkmbp6GS9Op0k/Agmpjuj9A=; b=eL67JtZh8e7/ASENYbAaEjbKL8CuQjVVuTh3CtKi42NfRo9JaIoXzQhdrGVamGEjz3eq +U5LtgF31xi2Yvs/yCMDDRot4maDNkl3lcb2onpqu3xQoTcnBGuw2/ItkzEgFe667AYUp O6Ql/Ace1mg5jPtqivXAOEuF2ycQvTNFYv0KMR11vjfeE3zb78mSKG3FsdCYJkaf8g/Iw l/z3lPDzxiK7cMkJGNsfN2kb6BPWOmwtFRDe5jpOBW+JL8b5D+2ogh8tmd2z+MyrQvvjI UQ/RMVCWc7C2ykADF8WfM+IWJjv5AoEd3ryxmocVo2MgyW4v1UyCgVuz4yz4nmWtJ4A== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=DUwnbP1r; 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 9AB83606A32C; Sat, 7 Nov 2026 15:01:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=DUwnbP1r Received: by smtp.kernel.org (Postfix) with ESMTPSA id 49B461F0089F; Sat, 7 Nov 2026 15:01:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794063691; bh=eeA49f8JeRLRTGiOktfxjkmbp6GS9Op0k/Agmpjuj9A=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=DUwnbP1rSOeMf9YiWJzYQ8aVNjnzmLIGDkCHdV7VD2doLHZs8pqc7EhfOAa7lu+8A GmhtcCQ3FIOrr+XySIwx4DpDZYCWy3APf0wrMLoeEQ7ANM1+/uf0M9LuzTGW5Mozi6 1OvafivT3/mzb9dK8M+EiFG+9v23fwSzmYTsVFV8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Dominik Maier , Jens Axboe , Sasha Levin Subject: [PATCH 6.18 797/869] loop: check for read-write open mode on LOOP_SET_STATUS in lo_compat_ioctl() Date: Sat, 7 Nov 2026 08:57:59 -0500 Message-ID: <20261107134919.825913383@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261107134852.069646174@linuxfoundation.org> References: <20261107134852.069646174@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore 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 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ 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 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 13ce229d450cd..57d3babbd63bf 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -1686,8 +1686,10 @@ static int lo_compat_ioctl(struct block_device *bdev, blk_mode_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 & BLK_OPEN_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