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 9DB402264AB; Sat, 12 Sep 2026 19:22:04 +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=1789240925; cv=none; b=HjYkZ90MzaElm5v9tY0g7bF2kkIs52GyiUpWv1I9YjjiDHF02IWuao9+Rp31chjPLcBUQdoLx22+VCRVE0YdEK+ov6Ye5w1/hUgmJXhrFppFnUpAPOrRUC/pwpeQDcVSuzP6y+nWtL6A6JvzR1556mGAx7csdPQrvINiCZxO6u8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789240925; c=relaxed/simple; bh=022RcbU7Muu2wv8YXlQzvwlZUP+1NPE5Nv7ojHEeJOk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=RTJ+ty43pcsT0qiM6MF/jY5n/AuxP3LcHRk0TAtSioK3wiTgqAbUnL6r3qUaI7yxGq6DmdXQxzs983LPGtU/GULyk9lyxWN9S94gCwSyYj7+qx1joS2LA7UOAVqKr3/77sNtLcF8Yd19qaNyCVwF9EOOuqnx4U5vWilBO3KGwwI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=wvB3uSn4; 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="wvB3uSn4" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BB0BA1F000FF; Sat, 12 Sep 2026 19:22:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789240924; bh=702d2z+OgCbstKfukgCXfXwMOwtnq9hY7ph6+6xyVu8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=wvB3uSn4o3vSSB30SP7Fc6kwSEdOt+ulJQq87u2rVd0/FNZtBTAnPOVJmtf/CZ0Xr j5y1EAXvGn1/KIL7MlaIEh0Y0eLudnGQZqorPxsbxIcGEl53jk/RoiWfANK4mQ5Tu/ MVojJVGmBO3pjkwRWSYKGv8c+XoBO5olA7lC+r+s= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Mike Snitzer , Chuck Lever Subject: [PATCH 5.10 031/798] NFSD: remove flawed WARN_ON_ONCE from nfsd_mode_check Date: Sat, 12 Sep 2026 08:54:19 +0200 Message-ID: <20260912065517.675468505@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260912065516.948645775@linuxfoundation.org> References: <20260912065516.948645775@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 5.10-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 @@ -69,10 +69,8 @@ nfsd_mode_check(struct svc_rqst *rqstp, 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; } /*