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=1793895826; b=zDYGcxR3UbgQFupgbwdYGF53cOb/+bAShs318Ng20JgJMpmFHgxc6x/edJP1Tw9FrJ7c /5MDN+4vyD0lODMzIsFf91cPuYnZ6h3F6Q234y/Cdg+YsgcSkRflVIlOOVs6IVsNO31Ql uibK93Drww9D9gG0+qzWMaoBsLVshy2bHzhEDwZdaW6rg4gku04WdAJyEcpBPWg6Bl+J3 uzxdR5gipkO5osSlX9Zgo5Jf1PqQW7furKJEFCBTheoO71NB6R1C+OG+Ci6jreCxGigg8 gTR3I08IAaKq4/Qhsy3840t5e4WGvTkmsDj79UZikAyiUIIse+mFR58pUAJ7Ghr8oAA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793895826; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=T5xP3xmvTREeNhGaQXZoBDRJasarUYjMXHgROJqFmHI=; b=e861ZBWSG826JTKDWlzx9QuOwWFP3usmRFetB4akecsXm6mScCWcGRF5IdVZ5C+l+Wfe j1HNpdN5TyKsTYW8nEX6ovdDeCkfAQX0nF7D2w0crfZpRBx1r1K6dFiL3Ohp2THq5FRuc pbm+xPMxodqMBLlYhD7FDdaCTnRNDCAgfxABycZgqgwxsAAcQU26u08pxa0yGhIOJoKEM I33f3LzGS3frXu06MgHLwwmsiudBWuzAON4NMN7Tuy6G74uLFidQXJW88TmSK9u3hiUAP e17KExqajQ/s1+c6BAZUDt4eLR5ixIGUdp2y2bE00IcNbt5Yi4LmMm5lmEMb1g2EyHg== 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=Z0t3Jxza; 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 338C1606A335 for ; Thu, 5 Nov 2026 16:23:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Z0t3Jxza Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7FA0D1F0093A; Thu, 5 Nov 2026 16:23:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793895826; bh=T5xP3xmvTREeNhGaQXZoBDRJasarUYjMXHgROJqFmHI=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Z0t3JxzaAhz63nMk0AobuhioVKJ/Ypw64MzmhRLZ9/xF53A0wSdEwOLjtF9d41JcI Z1dVgGblTF9AyzeiuyKGAT9H7W7M4987Fq805+pE6D1XlMjVWtjQ42xniPZBmGAhku FF6OGNkVBYEWDtmrWMcUD09/hmTKwbQirzlLvuUdXjveUz13Mhidm3J/ox8NdkL/Y5 5Thu4549WN+jit0C4zqW1rTghe9TktQAlNH62AORNvdCRMxVwzsVeYJvo+KwiJBgn6 wgd+9VnlkEd9lOtpU27oro9abTM6vGLl3IjeBQoJYsQx1YD0dCVxUb5m7UZkJODyIy mJXAwcSbnHRJw== From: Sasha Levin To: stable@vger.kernel.org Cc: Chris Mason , Josef Bacik , Amir Goldstein , Sasha Levin Subject: [PATCH 5.10.y] ovl: check that the parents of volatile/dirty are dirs Date: Thu, 5 Nov 2026 11:23:44 -0500 Message-ID: <20261105162313.1978922-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026110454-overstate-universe-e323@gregkh> References: <2026110454-overstate-universe-e323@gregkh> 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: Chris Mason [ Upstream commit e34d2ef818e4c7676d8d8e1bf43e6a1ed39efb2a ] An unprivileged user crashes the kernel by mounting overlayfs with the volatile option. A dentry that serves as the parent of a lookup must be a directory. ovl_create_volatile_dirty() walks work/incompat/volatile/dirty by name, and ovl_lookup_or_create() returns an existing entry whatever its type. A file or a symlink that another task creates during the mount becomes the parent of the next lookup, which calls a NULL ->lookup. An unprivileged user mounted overlayfs with "volatile" in a user namespace while a second process created a symlink named work/incompat, and the mount task oopsed on a NULL ->lookup call. Fix this by returning -ENOTDIR from ovl_lookup_or_create() when the caller asked for a directory and the existing entry is a non-dir. Fixes: c86243b090bc ("ovl: provide a mount option "volatile"") Cc: stable@vger.kernel.org Signed-off-by: Chris Mason Signed-off-by: Josef Bacik Signed-off-by: Amir Goldstein [ sashal: replaced end_creating(child) with dput(child) while retaining the existing explicit parent unlock ] Signed-off-by: Sasha Levin --- fs/overlayfs/super.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index 5d7df839902df..5b50a3c2289aa 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -1242,16 +1242,23 @@ static int ovl_check_rename_whiteout(struct dentry *workdir) } static struct dentry *ovl_lookup_or_create(struct dentry *parent, - const char *name, umode_t mode) + const char *name, bool is_dir) { size_t len = strlen(name); struct dentry *child; inode_lock_nested(parent->d_inode, I_MUTEX_PARENT); child = lookup_one_len(name, parent, len); - if (!IS_ERR(child) && !child->d_inode) - child = ovl_create_real(parent->d_inode, child, - OVL_CATTR(mode)); + if (!IS_ERR(child)) { + if (!child->d_inode) { + child = ovl_create_real(parent->d_inode, child, + OVL_CATTR(is_dir ? S_IFDIR : + S_IFREG)); + } else if (is_dir && !d_can_lookup(child)) { + dput(child); + child = ERR_PTR(-ENOTDIR); + } + } inode_unlock(parent->d_inode); dput(parent); @@ -1272,7 +1279,7 @@ static int ovl_create_volatile_dirty(struct ovl_fs *ofs) const char *const *name = volatile_path; for (ctr = ARRAY_SIZE(volatile_path); ctr; ctr--, name++) { - d = ovl_lookup_or_create(d, *name, ctr > 1 ? S_IFDIR : S_IFREG); + d = ovl_lookup_or_create(d, *name, ctr > 1); if (IS_ERR(d)) return PTR_ERR(d); } -- 2.53.0