Re: [PATCH net] i40e: prevent crash on probe if hw registers have invalid values

[Simon Horman <horms@kernel.org>]

On Fri, Oct 06, 2023 at 01:11:39PM +0200, Michal Schmidt wrote:
> The hardware provides the indexes of the first and the last available
> queue and VF. From the indexes, the driver calculates the numbers of
> queues and VFs. In theory, a faulty device might say the last index is
> smaller than the first index. In that case, the driver's calculation
> would underflow, it would attempt to write to non-existent registers
> outside of the ioremapped range and crash.
> 
> I ran into this not by having a faulty device, but by an operator error.
> I accidentally ran a QE test meant for i40e devices on an ice device.
> The test used 'echo i40e > /sys/...ice PCI device.../driver_override',
> bound the driver to the device and crashed in one of the wr32 calls in
> i40e_clear_hw.
> 
> Add checks to prevent underflows in the calculations of num_queues and
> num_vfs. With this fix, the wrong device probing reports errors and
> returns a failure without crashing.
> 
> Fixes: 838d41d92a90 ("i40e: clear all queues and interrupts")
> Signed-off-by: Michal Schmidt <mschmidt@redhat.com>

Reviewed-by: Simon Horman <horms@kernel.org>