linux-kernel - [PATCH AUTOSEL 4.9 2/3] cifs: Set CIFS_MOUNT_USE_PREFIX_PATH flag on setting cifs

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Message-Id: <20210215183716.122333-2-sashal@kernel.org>
Date:   Mon, 15 Feb 2021 13:37:15 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Shyam Prasad N <sprasad@...rosoft.com>,
        Aurelien Aptel <aaptel@...e.com>,
        Steve French <stfrench@...rosoft.com>,
        Sasha Levin <sashal@...nel.org>, linux-cifs@...r.kernel.org,
        samba-technical@...ts.samba.org
Subject: [PATCH AUTOSEL 4.9 2/3] cifs: Set CIFS_MOUNT_USE_PREFIX_PATH flag on setting cifs_sb->prepath.

From: Shyam Prasad N <sprasad@...rosoft.com>

[ Upstream commit a738c93fb1c17e386a09304b517b1c6b2a6a5a8b ]

While debugging another issue today, Steve and I noticed that if a
subdir for a file share is already mounted on the client, any new
mount of any other subdir (or the file share root) of the same share
results in sharing the cifs superblock, which e.g. can result in
incorrect device name.

While setting prefix path for the root of a cifs_sb,
CIFS_MOUNT_USE_PREFIX_PATH flag should also be set.
Without it, prepath is not even considered in some places,
and output of "mount" and various /proc/<>/*mount* related
options can be missing part of the device name.

Signed-off-by: Shyam Prasad N <sprasad@...rosoft.com>
Reviewed-by: Aurelien Aptel <aaptel@...e.com>
Signed-off-by: Steve French <stfrench@...rosoft.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/cifs/connect.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index af78de9ef036c..8508dc8270593 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -3488,6 +3488,7 @@ int cifs_setup_cifs_sb(struct smb_vol *pvolume_info,
 		cifs_sb->prepath = kstrdup(pvolume_info->prepath, GFP_KERNEL);
 		if (cifs_sb->prepath == NULL)
 			return -ENOMEM;
+		cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_USE_PREFIX_PATH;
 	}
 
 	return 0;
-- 
2.27.0