Re: [PATCH] proc: use vmalloc for our kernel buffer

[Josef Bacik]

On 8/13/20 12:19 PM, David Laight wrote:
> From: Josef Bacik
> > Sent: 13 August 2020 15:53
> >
> >    sysctl: pass kernel pointers to ->proc_handler
> >
> > we have been pre-allocating a buffer to copy the data from the proc
> > handlers into, and then copying that to userspace.  The problem is this
> > just blind kmalloc()'s the buffer size passed in from the read, which in
> > the case of our 'cat' binary was 64kib.  Order-4 allocations are not
> > awesome, and since we can potentially allocate up to our maximum order,
> > use vmalloc for these buffers.
>
> What happens if I run 'dd bs=16M ...' ?
>
> 	David

        /* don't even try if the size is too large */
        error = -ENOMEM;
        if (count >= KMALLOC_MAX_SIZE)
                goto out;

is above this code, thanks,

Josef