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 B89E13F9F2F; Fri, 4 Sep 2026 05:11:03 +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=1788498664; cv=none; b=FL0tXGWwywZWG4TtTZbCKAD/aFOtWxFRHBhZnK7y67RaSE2bHv6wWcXkkWI9xS4UbvuU+udvp6PrwG9bPZQDALpAx4SU5v90XaBWsB43nQCA0TczvEC4CFafRAPfmUvyOVJCdhx3BAkwAoEibc1KVdfefPqfsNAp9WwI5KS4MZ4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788498664; c=relaxed/simple; bh=XhgQiucMw4eWCtbkeDb2GTPQKI16x0R4Vm2/C81bGYo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=iGdTIaq0XqP1jkVbN9lIIVe30ycx/9bEjXeJN05Ij6r5Pyya9eW6s5uVybXFegtflOk+xoWCeuXT9qOWIRpku4QwGAZ8IWinc99ezSRxlRrjj62n7QkDwryZrlS8a8548XqTZnqi+4RBhQrpW3l7yCEtgfQ8wR57qHu4LGUBiTc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=15ccJQdq; 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="15ccJQdq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 198421F00A3D; Fri, 4 Sep 2026 05:11:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788498663; bh=XeYpvgSI4mMKaj0QfbHylLGTto1fe6MMCTlfa50x7xo=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=15ccJQdq4m+JLTh18Yw7rgiRXtm0VtLmFNDM3YUUKslVDdxZycl7b3z5y3IH68TSg O2YjtFvXgFDdzEjffEEIhcq10BVww/LedpPJ3FALUPT9WznfNh0GER3Qxon70YJDY9 kCXc6mNs5PT7pt4pg+dVi90vXH7LwKFR5tu9DKE8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Mike Snitzer , Chuck Lever Subject: [PATCH 7.2 143/713] NFSD: remove flawed WARN_ON_ONCE from nfsd_mode_check Date: Fri, 4 Sep 2026 06:51:51 +0200 Message-ID: <20260904045807.034693896@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: patches@lists.linux.dev 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: Mike Snitzer commit aa0cf48a448c5a9fe1a1e880899ecd589ce39e6e upstream. The header for commit e75b23f9e323 ("nfsd: check d_can_lookup in fh_verify of directories") details the assumption that justified adding the WARN_ON_ONCE to nfsd_mode_check(), that assumption is invalid (in the case of NFS reexport). When NFSD exports an NFS filesystem it is very possible for nfsd_mode_check() to encounter a @dentry that doesn't have i_op->lookup (see nfs_fhget()'s NFS_ATTR_FATTR_MOUNTPOINT and NFS_ATTR_FATTR_V4_REFERRAL handling, and d_flags_for_inode()). So remove nfsd_mode_check()'s WARN_ON_ONCE(). The nfserr_notdir return on that branch must stay. It guards the subsequent lookup_one_unlocked() -> __lookup_slow() path, which calls inode->i_op->lookup() with no NULL check, so returning nfserr_notdir is what keeps a client LOOKUP into such a @dentry from dereferencing a NULL method pointer. Fixes: e75b23f9e323 ("nfsd: check d_can_lookup in fh_verify of directories") Cc: stable@vger.kernel.org Signed-off-by: Mike Snitzer Link: https://patch.msgid.link/20260612191410.50177-1-snitzer@kernel.org Signed-off-by: Chuck Lever Signed-off-by: Greg Kroah-Hartman --- fs/nfsd/nfsfh.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) --- a/fs/nfsd/nfsfh.c +++ b/fs/nfsd/nfsfh.c @@ -70,10 +70,8 @@ nfsd_mode_check(struct dentry *dentry, u if (requested == 0) /* the caller doesn't care */ return nfs_ok; if (mode == requested) { - if (mode == S_IFDIR && !d_can_lookup(dentry)) { - WARN_ON_ONCE(1); + if (mode == S_IFDIR && !d_can_lookup(dentry)) return nfserr_notdir; - } return nfs_ok; } if (mode == S_IFLNK) {