linux-kernel - Re: [PATCH 3/9] VFS: Introduce a mount context

lists.openwall.net		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 linux-hardening linux-cve-announce 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:   Wed, 03 May 2017 11:43:47 -0700
From:   Joe Perches <joe@...ches.com>
To:     David Howells <dhowells@...hat.com>
Cc:     Jeff Layton <jlayton@...chiereds.net>, viro@...iv.linux.org.uk,
        linux-fsdevel@...r.kernel.org, linux-nfs@...r.kernel.org,
        linux-kernel@...r.kernel.org, mszeredi@...hat.com
Subject: Re: [PATCH 3/9] VFS: Introduce a mount context

On Wed, 2017-05-03 at 19:37 +0100, David Howells wrote:
> Joe Perches <joe@...ches.com> wrote:
> 
> > krealloc would probably be more efficient and possible
> > readable as likely there's already padding in the original
> > allocation.
> 
> The problem is if krealloc() fails: you've lost all those pointers to things
> you then need to free.

Huh?  How could that happen?

krealloc must always use a temporary.
If krealloc returns NULL, the original allocation is kept.

> > Are there no locking constraints?
> 
> Generally, no, not until you do the ->mount() op.  Also remounting needs a
> lock, but that's already done with the sb->s_umount lock.
> 
> However, that said, if you do:
> 
> 	fd = fsopen("foofs");
> 	write(fd, "o foo=bar", ...);
> 	fsmount(fd, "/foo");
> 
> then the fsmount() and write() calls have to lock against other fsmount() and
> write() calls.  I use the inode lock for this.  [Note that it probably should
> be interruptible rather than just killable, but there's no primitive for that
> as yet].
> 
> David