linux-kernel - [PATCH 5.4 17/72] cifs: fix DFS mount with cifsacl/modefromsid

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Message-Id: <20200921163122.692523738@linuxfoundation.org>
Date:   Mon, 21 Sep 2020 18:30:56 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ronnie Sahlberg <lsahlber@...hat.com>,
        "Paulo Alcantara (SUSE)" <pc@....nz>,
        Steve French <stfrench@...rosoft.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 17/72] cifs: fix DFS mount with cifsacl/modefromsid

From: Ronnie Sahlberg <lsahlber@...hat.com>

[ Upstream commit 01ec372cef1e5afa4ab843bbaf88a6fcb64dc14c ]

RHBZ: 1871246

If during cifs_lookup()/get_inode_info() we encounter a DFS link
and we use the cifsacl or modefromsid mount options we must suppress
any -EREMOTE errors that triggers or else we will not be able to follow
the DFS link and automount the target.

This fixes an issue with modefromsid/cifsacl where these mountoptions
would break DFS and we would no longer be able to access the share.

Signed-off-by: Ronnie Sahlberg <lsahlber@...hat.com>
Reviewed-by: Paulo Alcantara (SUSE) <pc@....nz>
Signed-off-by: Steve French <stfrench@...rosoft.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/cifs/inode.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index eb2e3db3916f0..17df90b5f57a2 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -898,6 +898,8 @@ cifs_get_inode_info(struct inode **inode, const char *full_path,
 	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MODE_FROM_SID) {
 		rc = cifs_acl_to_fattr(cifs_sb, &fattr, *inode, true,
 				       full_path, fid);
+		if (rc == -EREMOTE)
+			rc = 0;
 		if (rc) {
 			cifs_dbg(FYI, "%s: Get mode from SID failed. rc=%d\n",
 				__func__, rc);
@@ -906,6 +908,8 @@ cifs_get_inode_info(struct inode **inode, const char *full_path,
 	} else if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_CIFS_ACL) {
 		rc = cifs_acl_to_fattr(cifs_sb, &fattr, *inode, false,
 				       full_path, fid);
+		if (rc == -EREMOTE)
+			rc = 0;
 		if (rc) {
 			cifs_dbg(FYI, "%s: Getting ACL failed with error: %d\n",
 				 __func__, rc);
-- 
2.25.1