From nobody Tue Apr 7 21:24:03 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 A108336922D; Wed, 11 Mar 2026 21:56:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773266199; cv=none; b=I4ESwIsdzQA962FkCoU5TQuUar0Yvx1qzBa6RkgedX77Ngb2m36S4lzkhasSjPC9rPXPf4FWJ1aZtOXrmNAd1hCu9CBdMAeRK4a1E1vSJCUh6mpBefsXv8ma10modnkOrDLf/W9YqUZomcNB8mTJDc7zL6ANKcu71JJWw+jtVlY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773266199; c=relaxed/simple; bh=aJXunCWUMwo/RoSO3Pr5eSrF9qPQim1AZ9jP0b2ptO0=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=nydrLjF2VkIdlJsmmWVMPxEazPnurJjUvJ3tU8r8lRuuT7TmDmv7QhO66YNblEMzdgUJwoiKq61zoH3iX58apgKXP8DAMFKyD/5xgTT866w1KFnFAWxAh6XDNNklMyHAFZT2m4BhAvsPONylDfRTft9XuU4SwaZ485l/z/Uoqlo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=TJp2G6OT; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="TJp2G6OT" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6795DC116C6; Wed, 11 Mar 2026 21:56:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773266199; bh=aJXunCWUMwo/RoSO3Pr5eSrF9qPQim1AZ9jP0b2ptO0=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=TJp2G6OTzu/6nnsaqW4Cz+osmsS4bx7y5wQT0CzW3JUItLgwURYj/ZO/YtUrLGcYb pN+8FYiVWfJan9bAsg2nBoP1857W9wLMqnCyLeLpk00HektiL1PszGYa4phbPTO0gG US/3+xX59eGPmsGcK8hsIRmwvrB+9W2wlAjA9rtXKDPdLj4WhnD/OtJ/c5BkccBu5y j7SOVfyKrhSwRwPPJeiSGPrnt2GmKndHMm6GroQFs07egwDT70xPvZ9ktPedV161VQ Tkfi2+43vjK9CLbjZLN3k7Pq4PEAMpmxdsLg3OsTxLGjamr65ICazCDl4sikZ67Bge 2CT/9Fu6tTgSQ== From: Christian Brauner Date: Wed, 11 Mar 2026 22:43:54 +0100 Subject: [PATCH RFC v3 11/26] coredump: use scoped_with_init_fs() for coredump path resolution Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260311-work-kthread-nullfs-v3-11-3dd2cbe92ad0@kernel.org> References: <20260311-work-kthread-nullfs-v3-0-3dd2cbe92ad0@kernel.org> In-Reply-To: <20260311-work-kthread-nullfs-v3-0-3dd2cbe92ad0@kernel.org> To: linux-fsdevel@vger.kernel.org Cc: Linus Torvalds , linux-kernel@vger.kernel.org, Alexander Viro , Jens Axboe , Jan Kara , Tejun Heo , Jann Horn , Christian Brauner X-Mailer: b4 0.15-dev-9fd7c X-Developer-Signature: v=1; a=openpgp-sha256; l=1539; i=brauner@kernel.org; h=from:subject:message-id; bh=aJXunCWUMwo/RoSO3Pr5eSrF9qPQim1AZ9jP0b2ptO0=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMWRufPIz3nvqV949z8u8VZa9rNqX1LiI50vJvKWPNcOuH Xhu2JlR2lHKwiDGxSArpsji0G4SLrecp2KzUaYGzBxWJpAhDFycAjCRib8Y/jtVF/KskWiaXnl1 5YkQh4W1J+ze/J5y7O3UuBlH/XK/mi5lZLhurzdRIGD6zne5E66pvdhx+27F0Sc7TE+xTvVn0Wa 6JMMEAA== X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 Use scoped_with_init_fs() to temporarily override current->fs for the filp_open() call so the coredump path lookup happens in init's filesystem context. This replaces the init_root() + file_open_root() pattern with the simpler scoped override. coredump_file() =E2=86=90 do_coredump() =E2=86=90 vfs_coredump() =E2=86=90 = get_signal() =E2=80=94 runs as the crashing userspace process Uses init's root to prevent a chrooted/user-namespaced process from controlling where suid coredumps land. Not a kthread, but intentionally needs init's fs for security. Signed-off-by: Christian Brauner --- fs/coredump.c | 11 +++-------- 1 file changed, 3 insertions(+), 8 deletions(-) diff --git a/fs/coredump.c b/fs/coredump.c index 29df8aa19e2e..7428349f10bf 100644 --- a/fs/coredump.c +++ b/fs/coredump.c @@ -919,15 +919,10 @@ static bool coredump_file(struct core_name *cn, struc= t coredump_params *cprm, * with a fully qualified path" rule is to control where * coredumps may be placed using root privileges, * current->fs->root must not be used. Instead, use the - * root directory of init_task. + * root directory of PID 1. */ - struct path root; - - task_lock(&init_task); - get_fs_root(init_task.fs, &root); - task_unlock(&init_task); - file =3D file_open_root(&root, cn->corename, open_flags, 0600); - path_put(&root); + scoped_with_init_fs() + file =3D filp_open(cn->corename, open_flags, 0600); } else { file =3D filp_open(cn->corename, open_flags, 0600); } --=20 2.47.3