lkml.org 
[lkml]   [2018]   [Oct]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v6 1/1] ns: add binfmt_misc to the user namespace
From
Date
On 2018-10-10 18:14, Laurent Vivier wrote:

> + /* create a new binfmt namespace
> + * if we are not in the first user namespace
> + * but the binfmt namespace is the first one
> + */
> + if (READ_ONCE(ns->binfmt_ns) == NULL) {
> + struct binfmt_namespace *new_ns;
> +
> + new_ns = kmalloc(sizeof(struct binfmt_namespace),
> + GFP_KERNEL);
> + if (new_ns == NULL)
> + return -ENOMEM;
> + INIT_LIST_HEAD(&new_ns->entries);
> + new_ns->enabled = 1;
> + rwlock_init(&new_ns->entries_lock);
> + new_ns->bm_mnt = NULL;
> + new_ns->entry_count = 0;
> + /* ensure new_ns is completely initialized before sharing it */
> + smp_wmb();
> + WRITE_ONCE(ns->binfmt_ns, new_ns);
> + }

If ns->binfmt_ns can really change under us (given you use READ_ONCE),
what prevents two instances of this code running at the same time, in
which case one of them would leak its new_ns instance? Also, there
doesn't seem to be any smp_rmb() buddy to that wmb(), I don't think
that's implied by READ_ONCE() in binfmt_ns().

Rasmus

\
 
 \ /
  Last update: 2018-10-16 12:14    [W:0.093 / U:8.188 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site