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Date: Fri, 6 Oct 2023 14:13:41 +0200
From: Simon Horman <horms@kernel.org>
To: Michal Schmidt <mschmidt@redhat.com>
Cc: intel-wired-lan@lists.osuosl.org, netdev@vger.kernel.org,
	Jeff Kirsher <jeffrey.t.kirsher@intel.com>,
	Shannon Nelson <shannon.nelson@amd.com>,
	Tony Nguyen <anthony.l.nguyen@intel.com>,
	Jesse Brandeburg <jesse.brandeburg@intel.com>
Subject: Re: [PATCH net] i40e: prevent crash on probe if hw registers have
 invalid values
Message-ID: <ZR/59YSFavmHAHC7@kernel.org>
References: <20231006111139.1560132-1-mschmidt@redhat.com>
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In-Reply-To: <20231006111139.1560132-1-mschmidt@redhat.com>

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>