linux-kernel - Re: [PATCH v2] nvme: Define compat_ioctl again to unbreak 32-bit userspace.

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Message-ID: <06b571a5-4d0f-2112-c73b-35618b652a3b@linux.alibaba.com>
Date:   Thu, 21 Jul 2022 14:34:45 +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 v2] nvme: Define compat_ioctl again to unbreak 32-bit
 userspace.

LGTM,

Reviewed-by: Guixin Liu <kanie@...ux.alibaba.com>

在 2022/7/21 11:57, 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
>
> The blkdev_compat_ptr_ioctl helper can be used to direct compat calls
> through the main ioctl handler and makes things work again.
>
> Fixes: 89b3d6e60550 ("nvme: simplify the compat ioctl handling")
> Signed-off-by: Nick Bowler <nbowler@...conx.ca>
> ---
>
> v2: use blkdev_compat_ptr_ioctl as suggested by Christoph Hellwig
>
>   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 6a12a906a11e..9c75d7378d31 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -2123,6 +2123,7 @@ 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	= blkdev_compat_ptr_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 d3e2440d8abb..432ea9793a84 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	= blkdev_compat_ptr_ioctl,
>   	.getgeo		= nvme_getgeo,
>   	.report_zones	= nvme_ns_head_report_zones,
>   	.pr_ops		= &nvme_pr_ops,