linux-kernel - Re: [PATCH] nvme: Define compat_ioctl again to unbreak 32-bit userspace.

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Message-ID: <20220720042726.GA5574@lst.de>
Date:   Wed, 20 Jul 2022 06:27:26 +0200
From:   Christoph Hellwig <hch@....de>
To:     Nick Bowler <nbowler@...conx.ca>
Cc:     linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH] nvme: Define compat_ioctl again to unbreak 32-bit
 userspace.

On Tue, Jul 19, 2022 at 09:55:38PM -0400, Nick Bowler wrote:
> Commit 89b3d6e60550 ("nvme: simplify the compat ioctl handling") removed
> the initialization of compat_ioctl from the nvme block_device_operations
> structures.
> 
> Presumably the expectation was that 32-bit ioctls would be directed
> through the regular handler but this is not the case: failing to assign
> .compat_ioctl actually means that the compat case is disabled entirely,
> and any attempt to submit nvme ioctls from 32-bit userspace fails
> outright with -ENOTTY.

I don't think wiring up the native version is the right thing to do,
this needs to be blkdev_compat_ptr_ioctl, just like we use
compat_ptr_ioctl for the character device nodes.