linux-kernel - Re: [PATCH 14/33] vfs: Implement a filesystem superblock creation/configuration context [ver #11]

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Date:   Tue, 18 Sep 2018 18:40:53 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     David Howells <dhowells@...hat.com>
Cc:     Guenter Roeck <linux@...ck-us.net>, viro@...iv.linux.org.uk,
        torvalds@...ux-foundation.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Subject: Re: [PATCH 14/33] vfs: Implement a filesystem superblock
 creation/configuration context [ver #11]

On (09/18/18 18:07), Sergey Senozhatsky wrote:
> emergency_remount()
>  do_emergency_remount()
>   do_emergency_remount_callback()
>    reconfigure_super()
> 
> At fc->ops dereference:
> 
>  981         if (fc->ops->reconfigure) {
> 		^^^^^^^^^
>  982                 retval = fc->ops->reconfigure(fc);
>  983                 if (retval == 0) {
>  984                         security_sb_reconfigure(fc);
> 
> 
> So the check either better be
> 
> 	if (fc->ops && fc->ops->reconfigure)

I guess I was pretty lucky to have leading zeroes in that fc.

David, do you want to add a macro which would make `struct fs_context fc'
misuse less possible? There are 3 users right now who don't use
vfs_new_fs_context(), and none of them appear to properly set all of
`struct fs_context fc' members. This can cause problems in the future,
right?

fs/namespace.c: struct fs_context fc = {
fs/super.c:                     struct fs_context fc = {
fs/super.c:     struct fs_context fc = {

	-ss