lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Thu, 31 Jan 2019 09:40:59 -0800
From:   "Darrick J. Wong" <>
To:     Dave Chinner <>
Cc:     Wang Shilong <>,,,, Wang Shilong <>,
        Andreas Dilger <>, Li Xi <>
Subject: Re: [RFC PATCH] ext4: add link file support for {GET,SET}XATTR ioctl

On Thu, Jan 31, 2019 at 02:41:06PM +1100, Dave Chinner wrote:
> On Thu, Jan 31, 2019 at 10:47:12AM +0900, Wang Shilong wrote:
> > From: Wang Shilong <>
> > 
> > Currently there is no way to change project ID of
> > symlink file itself, this is important to implement
> > Directory quota for an existed directory.
> This seems like something open(O_PATH|O_NOFOLLOW) should allow.
> from open(2):

...but I thought O_PATH|O_NOFOLLOW file descriptions didn't allow ioctl

$ ln -sf urk /mnt/cow
$ xfs_io -c 'open -PL /mnt/cow' -c 'chproj 6'
setprojid: Bad file descriptor
$ ls -la /mnt/
lrwxrwxrwx 1 root root 3 Jan 31 09:30 /mnt/cow -> moo

> 	If pathname is a symbolic link and the O_NOFOLLOW flag is
> 	also specified, then the call returns a file  descriptor
> 	referring  to  the symbolic  link.  This  file  descriptor
> 	can  be used as the dirfd argument in calls to fchownat(2),
> 	fstatat(2), linkat(2), and read¿ linkat(2) with an empty
> 	pathname to have the calls operate on the symbolic link.
> Changing the project id is the equivalent of fchownat().....

/me & others wonder (on the ext4 call) if maybe we should promote
project id to a vfs level concept?  i.e. store project id in struct
inode instead of the fs-specific inode structures.  Then we can use the
existing setattr infrastructure to persist those changes.

As for fchownat, how about a new flag that means "use the value in the
gid field to set the project id"?


> Cheers,
> Dave.
> -- 
> Dave Chinner

Powered by blists - more mailing lists