Re: [PATCH v4 4/9] epoll: Add implementation for epoll_ctl_batch

[Fam Zheng]

On Tue, 03/10 09:59, Dan Rosenberg wrote:
> On 03/09/2015 09:49 PM, Fam Zheng wrote:
> > +	if (!cmds || ncmds <= 0 || ncmds > EP_MAX_BATCH)
> > +		return -EINVAL;
> > +	cmd_size = sizeof(struct epoll_ctl_cmd) * ncmds;
> > +	/* TODO: optimize for small arguments like select/poll with a stack
> > +	 * allocated buffer */
> > +
> > +	kcmds = kmalloc(cmd_size, GFP_KERNEL);
> > +	if (!kcmds)
> > +		return -ENOMEM;
> You probably want to define EP_MAX_BATCH as some sane value much less
> than INT_MAX/(sizeof(struct epoll_ctl_cmd)). While this avoids the
> integer overflow from before, any user can cause the kernel to kmalloc
> up to INT_MAX bytes. Probably not a huge deal because it's freed at the
> end of the syscall, but generally not a great idea.
> 

Yeah, makes sense, any suggested value?

Thanks,
Fam
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/