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 54A9624A05D; Fri, 4 Sep 2026 05:05:18 +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=1788498319; cv=none; b=TGXRuBqtR5M7ZVqwrPjmydLune7iRFkO6y5c3WA3XPQl+DaV2gYP0bjC46BpSNglzXNMLaOG+JfscrFj9Y+pHg43Y5htbT7XfRxUzoQQ4/h9csCVke2SzdcLWwXoO5QhOiS3zDRFWKPAnuBxi0fLtmfPYltq6Ageim8PIG/NZU0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788498319; c=relaxed/simple; bh=oHIeZp3PKlCp0OJ1iASUnEwVmpDVVaSGJUdAM4KKqCY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=r258Y3a8YSLWZuzWoQklvEgvuN0Vwg6YlkKvySyM5dtfEG8OM2ibFUYPtmklBj1H6H3YT4A+FIMrSKaHrUvkjXHQW8QeNqplGtv8eboPD1nI7jHM14bP7d1IG8Ii8RyR2sZAWIXVEeFYMdGOMSCVuGhWqb2OLqy4abia0q9JCrc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Sg3HUrt7; 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="Sg3HUrt7" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AFEE21F00A3D; Fri, 4 Sep 2026 05:05:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788498318; bh=PFtyjQfmENkyjDW1Q1nMiMInouDBG7FYcN83IrEO3/g=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Sg3HUrt7SLxrTxWRygtSM0trUwpttuoFT9nq3v9w3g2rAnN5JSg/kNg6wMCZfkght 5/pEpv6qjkf4XQG5GmMYMw3eZR2+dLGgqr/1y4B+R9I9TIYtAmiYBP/vb7TGqiU05s FmfcZORh19QvyNx9nHm/il3tbfEEj0pqLeK2PEbw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Vivek Parikh , Amir Goldstein , "Christian Brauner (Amutable)" Subject: [PATCH 7.2 020/713] ovl: fix double end_creating() on the casefold-mismatch path Date: Fri, 4 Sep 2026 06:49:48 +0200 Message-ID: <20260904045804.278441515@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260904045803.810145556@linuxfoundation.org> References: <20260904045803.810145556@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org 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: Vivek Parikh commit 077ab8985ee278c3d8618182d335b0f0cd919e16 upstream. ovl_create_real() releases the new dentry twice when the casefold consistency check fails. The S_IFDIR branch calls end_creating() and sets err, then falls through to the common out: label which calls end_creating() on the same dentry again: case S_IFDIR: newdentry = ovl_do_mkdir(ofs, dir, newdentry, attr->mode); err = PTR_ERR_OR_ZERO(newdentry); if (!err && ofs->casefold != ovl_dentry_casefolded(newdentry)) { pr_warn_ratelimited(...); end_creating(newdentry); /* first */ err = -EINVAL; } break; ... if (err) goto out; ... out: if (err) { end_creating(newdentry); /* second, same dentry */ return ERR_PTR(err); } end_creating() is end_dirop(), which does inode_unlock() on the parent and dput() on the dentry, so the parent directory's i_rwsem is unlocked twice and the dentry is put twice. The second unlock releases a lock that is not held, which is what wedges every later creation under that parent, and the second dput() drops a reference that was never taken. The branch was added by commit dfc7da402ccc ("ovl: Check for casefold consistency when creating new dentries") as a bare dput(), which already released the reference twice; commit fe497f0759e0 ("VFS: change vfs_mkdir() to unlock on failure.") converted both sites to end_creating(), adding the double unlock. This is reachable by an unprivileged user. The casefold consistency of the layers is validated at mount time in ovl_parse_layer(), and again on every lookup in ovl_lookup_single(), but ofs->workdir is the internal "work" subdirectory created inside the user-supplied workdir, and that subdirectory is not re-checked. Marking it casefolded after the mount therefore makes every ovl_create_temp() inherit the wrong state - and that path reaches ovl_create_real() through ovl_start_creating_temp(), which uses start_creating() with a generated name and so never runs the lookup-time check. unshare -Urm mount -t tmpfs -o casefold=utf8-12.1.0 tmpfs mnt mkdir -p mnt/lower/d mnt/upper mnt/work mnt/merged mount -t overlay ovl -o lowerdir=mnt/lower,\ upperdir=mnt/upper,workdir=mnt/work mnt/merged chattr +F mnt/work/work mkdir mnt/merged/d/sub # directory copy-up overlayfs: wrong inherited casefold (work/#5) and the next copy-up blocks forever on the parent's i_rwsem: mkdir D start_creating+0x65/0xb0 ovl_start_creating_temp+0xb0/0xe0 [overlay] ovl_create_temp+0xa3/0x1d0 [overlay] ovl_copy_up_one+0x1f1c/0x21c0 [overlay] ovl_copy_up_flags+0xf5/0x140 [overlay] ovl_create_object+0xb7/0x220 [overlay] ovl_mkdir+0x23/0x40 [overlay] Drop the end_creating() from the branch and let out: own the cleanup, which is what every other error path in this function already does. Fixes: dfc7da402ccc ("ovl: Check for casefold consistency when creating new dentries") Cc: stable@vger.kernel.org Signed-off-by: Vivek Parikh Reviewed-by: Amir Goldstein Signed-off-by: Christian Brauner (Amutable) Signed-off-by: Greg Kroah-Hartman --- fs/overlayfs/dir.c | 1 - 1 file changed, 1 deletion(-) --- a/fs/overlayfs/dir.c +++ b/fs/overlayfs/dir.c @@ -188,7 +188,6 @@ struct dentry *ovl_create_real(struct ov if (!err && ofs->casefold != ovl_dentry_casefolded(newdentry)) { pr_warn_ratelimited("wrong inherited casefold (%pd2)\n", newdentry); - end_creating(newdentry); err = -EINVAL; } break;