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


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