RE: [EXTERNAL] [PATCH 5.4 303/309] cifs: fix mode bits from dir listing when mounted with modefromsid

[Pavel Shilovskiy]

-----Original Message Begin-----
From: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> 
Sent: Monday, February 10, 2020 4:34 AM
To: linux-kernel@xxxxxxxxxxxxxxx
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>; stable@xxxxxxxxxxxxxxx; Aurelien Aptel <aaptel@xxxxxxxx>; Steven French <Steven.French@xxxxxxxxxxxxx>; Pavel Shilovskiy <pshilov@xxxxxxxxxxxxx>
Subject: [EXTERNAL] [PATCH 5.4 303/309] cifs: fix mode bits from dir listing when mounted with modefromsid

From: Aurelien Aptel <aaptel@xxxxxxxx>

commit e3e056c35108661e418c803adfc054bf683426e7 upstream.

When mounting with -o modefromsid, the mode bits are stored in an ACE. Directory enumeration (e.g. ls -l /mnt) triggers an SMB Query Dir which does not include ACEs in its response. The mode bits in this case are silently set to a default value of 755 instead.

This patch marks the dentry created during the directory enumeration as needing re-evaluation (i.e. additional Query Info with ACEs) so that the mode bits can be properly extracted.

Quick repro:

$ mount.cifs //win19.test/data /mnt -o ...,modefromsid $ touch /mnt/foo && chmod 751 /mnt/foo $ stat /mnt/foo
  # reports 751 (OK)
$ sleep 2
  # dentry older than 1s by default get invalidated $ ls -l /mnt
  # since dentry invalid, ls does a Query Dir
  # and reports foo as 755 (WRONG)

Signed-off-by: Aurelien Aptel <aaptel@xxxxxxxx>
Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
CC: Stable <stable@xxxxxxxxxxxxxxx>
Reviewed-by: Pavel Shilovsky <pshilov@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/cifs/readdir.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/cifs/readdir.c
+++ b/fs/cifs/readdir.c
@@ -174,7 +174,8 @@ cifs_fill_common_info(struct cifs_fattr
 	 * may look wrong since the inodes may not have timed out by the time
 	 * "ls" does a stat() call on them.
 	 */
-	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_CIFS_ACL)
+	if ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_CIFS_ACL) ||
+	    (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MODE_FROM_SID))
 		fattr->cf_flags |= CIFS_FATTR_NEED_REVAL;
 
 	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_UNX_EMUL &&

-----Original Message End-----

Hi Greg,

This patch fixes the following commit that was introduced in v5.5:

commit fdef665ba44ad5ed154af2acfb19ae2ee3bf5dcc
Author: Steve French <stfrench@xxxxxxxxxxxxx>
Date:   Fri Dec 6 02:02:38 2019 -0600

    smb3: fix mode passed in on create for modetosid mount option


Please remove the patch from all stable trees expect 5.5.y.

--
Best regards,
Pavel Shilovsky