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 681D541A766; Fri, 4 Sep 2026 06:07:34 +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=1788502055; cv=none; b=t9uziHNlznfrnNboWZJM13tssU2at6lXyXpMKoOBuBf8uCtuhwgzTwJoPoV+NM7xt60kiUIgusS6S30+05VJ0b5EXdg5/guTjbnjzkpA2JC4lDa73bSUTqpyYm0om2HGy8umZDnPsrpkZ74/nkepcXlkVUqMCfm3nEZbvxr5/Xo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788502055; c=relaxed/simple; bh=vlPbUAPXYmdI5hOnURERUJujeWJapbiXTnlheO0DgYU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Q0urevosC4Tk6v4pf6apxYRFrH/BwYHnhsngG7ZVcwHNxxnEKg5gm9BC8gKVwFyl6r0ZkJrOB0N2N+NDZeYA15dNcBEx2bw8A5hVTXa2DY5799qDTEGvujy+q0J85PE39yQKKpLo+3dI8KUhaLHTmJzGPmcfS3fEvkTU32+BRc4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=zw8f47ds; 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="zw8f47ds" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 712721F00A3D; Fri, 4 Sep 2026 06:07:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788502054; bh=3zqkH8RpGWZdnbIIm3TIShX9XHyBrqMMnMH6F6hsmhA=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=zw8f47dsWBj+fdX3fUDcs0BkeBR2YxDXSbNzmldqEUtTNrk19jkoW4UnjlF0nUXpe vseh9gH6ecIgUIt6m9UIGmGqWCwESMp+N85kTfiwGtzhBmw9AhK2eh43pnsxB3YQAR bEmgVgO7J7Y+6PwM+hyoLzqknPkCqVHCQ0Jc+ncs= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Mike Snitzer , Chuck Lever Subject: [PATCH 6.12 072/403] NFSD: remove flawed WARN_ON_ONCE from nfsd_mode_check Date: Fri, 4 Sep 2026 06:57:55 +0200 Message-ID: <20260904045736.472113460@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260904045734.806166532@linuxfoundation.org> References: <20260904045734.806166532@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 6.12-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 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) {