On Thu, 2014-01-09 at 10:51 -0500, Steven Rostedt wrote:
> On Thu, 9 Jan 2014 10:31:55 -0500
> Eric Paris <eparis@xxxxxxxxxxxxxx> wrote:
>
> > Didn't Al find this/something very similar. I really hate this
>
> I'm not involved with the vfs, so I'm unaware of other solutions
> presented. I just hit this now and solving bugs is where I get a chance
> to learn about other aspects of the kernel. ;-)
>
> > solution. Why should every LSM try to understand the intimate
> > lifetime rules of the parent subsystems? The real problem is that
> > inode_free_security() is being called while the inode is still in use.
> > While I agree with the assessment, I disagree with the solution. Let
> > me try to find where Al and Christoph talked about this....
> >
>
> The other obvious solution (but not as trivial to implement) is to call
> the security_inode_free() and friends (probably __destroy_inode()
> itself) after a synchronize_rcu().
>
> Perhaps something like this?
I can't for the life of me find that conversation! Maybe I'm just
making it all up... Usually I forget conversations, not remember ones
that didn't happen...
Assuming the VFS guys say that delaying __destroy_inode() is safe like
that, I like it better. It also means that this is fixed for all LSMs,
not just SELinux...
-Eric
>
> -- Steve
>
> diff --git a/fs/inode.c b/fs/inode.c
> index 4bcdad3..a8f3b88 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -252,16 +252,17 @@ EXPORT_SYMBOL(__destroy_inode);
> static void i_callback(struct rcu_head *head)
> {
> struct inode *inode = container_of(head, struct inode, i_rcu);
> + __destroy_inode(inode);
> kmem_cache_free(inode_cachep, inode);
> }
>
> static void destroy_inode(struct inode *inode)
> {
> BUG_ON(!list_empty(&inode->i_lru));
> - __destroy_inode(inode);
> - if (inode->i_sb->s_op->destroy_inode)
> + if (inode->i_sb->s_op->destroy_inode) {
> + __destroy_inode(inode);
> inode->i_sb->s_op->destroy_inode(inode);
> - else
> + } else
> call_rcu(&inode->i_rcu, i_callback);
> }
>
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