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

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Date:   Wed, 20 Jul 2022 11:51:01 +0800
From:   Guixin Liu <kanie@...ux.alibaba.com>
To:     Nick Bowler <nbowler@...conx.ca>, linux-nvme@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Cc:     Christoph Hellwig <hch@....de>
Subject: Re: [PATCH] nvme: Define compat_ioctl again to unbreak 32-bit
 userspace.

Hi Nick,

Should this in the brace of "#ifdef CONFIG_COMPAT" and "#endif"?

best regards,

Guixin Liu

在 2022/7/20 09:55, Nick Bowler 写道:
> 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.
>
> For example:
>
>    % smartctl -x /dev/nvme0n1
>    [...]
>    Read NVMe Identify Controller failed: NVME_IOCTL_ADMIN_CMD: Inappropriate ioctl for device
>
> Direct .compat_ioctl to the main ioctl handlers in order to make things
> work again.
>
> Fixes: 89b3d6e60550 ("nvme: simplify the compat ioctl handling")
> Signed-off-by: Nick Bowler <nbowler@...conx.ca>
> ---
>   drivers/nvme/host/core.c      | 1 +
>   drivers/nvme/host/multipath.c | 1 +
>   2 files changed, 2 insertions(+)
>
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index a2862a56fadc..30e105dbc178 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -2093,6 +2093,7 @@ static int nvme_report_zones(struct gendisk *disk, sector_t sector,
>   static const struct block_device_operations nvme_bdev_ops = {
>   	.owner		= THIS_MODULE,
>   	.ioctl		= nvme_ioctl,
> +	.compat_ioctl	= nvme_ioctl,
>   	.open		= nvme_open,
>   	.release	= nvme_release,
>   	.getgeo		= nvme_getgeo,
> diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
> index d464fdf978fb..0f38a5feec22 100644
> --- a/drivers/nvme/host/multipath.c
> +++ b/drivers/nvme/host/multipath.c
> @@ -408,6 +408,7 @@ const struct block_device_operations nvme_ns_head_ops = {
>   	.open		= nvme_ns_head_open,
>   	.release	= nvme_ns_head_release,
>   	.ioctl		= nvme_ns_head_ioctl,
> +	.compat_ioctl	= nvme_ns_head_ioctl,
>   	.getgeo		= nvme_getgeo,
>   	.report_zones	= nvme_ns_head_report_zones,
>   	.pr_ops		= &nvme_pr_ops,