Re: [scsi] 6aded12b10: kernel_BUG_at_mm/usercopy.c

[Kees Cook]

On Wed, Mar 23, 2022 at 04:47:39PM +0100, Christoph Hellwig wrote:
> On Wed, Mar 23, 2022 at 08:40:30AM -0700, Kees Cook wrote:
> > Regardless, I'm concerned that disabling PAGESPAN will just uncover
> > further checks, though. Where is allocation happening? The check is here:
> 
> blk_mq_alloc_rqs, using alloc_pages_node.  This hasn't actually changed
> with this comment.  Just the size of the allocation shrunk, probably
> leading to the span of pages.

Okay, the page allocator _should_ be fine for that. In the mean time,
lkp should probably just disable PAGESPAN.

> > I *think* the allocation is happening in scsi_ioctl_reset()? But that's
> > a plain kmalloc(), so I'm not sure why PAGESPAN would have tripped...
> > are there other allocation paths?
> 
> scsi_ioctl_reset is the odd one out and does also allocate a request,
> but that request is never used for user copies (and that whole hacky
> side path needs to go away, there is a huge series that needs to be
> finished to sort this out).

Gotcha!

-- 
Kees Cook