RE: [PATCH V2] nvme: Add compat_ioctl handler for NVME_IOCTL_SUBMIT_IO

[<masahiro31.yamada@kioxia.com>]

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>Currently 32 bit application gets ENOTTY when it calls
>compat_ioctl with NVME_IOCTL_SUBMIT_IO in 64 bit kernel.
>
>The cause is that the results of sizeof(struct nvme_user_io),
>which is used to define NVME_IOCTL_SUBMIT_IO,
>are not same between 32 bit compiler and 64 bit compiler.
>
>* 32 bit: the result of sizeof nvme_user_io is 44.
>* 64 bit: the result of sizeof nvme_user_io is 48.
>
>64 bit compiler seems to add 32 bit padding for multiple of 8 bytes.
>
>This patch adds a compat_ioctl handler.
>The handler replaces NVME_IOCTL_SUBMIT_IO32 with NVME_IOCTL_SUBMIT_IO
>in case 32 bit application calls compat_ioctl for submit in 64 bit kernel.
>Then, it calls nvme_ioctl as usual.
>
>Signed-off-by: Masahiro Yamada (KIOXIA) <masahiro31.yamada@kioxia.com>
>---
>v2:
>- Add a comment explaining what is going on in nvme_compat_ioctl()
>- Put nvme_compat_ioctl() under CONFIG_COMPAT and add #else branch
>- Move struct nvme_user_io32 #ifdef CONFIG_COMPAT block in core.c
>- Fix packed pragma warning by checkpatch.pl
>  WARNING: __packed is preferred over __attribute__((packed))
>
> drivers/nvme/host/core.c | 45 ++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 43 insertions(+), 2 deletions(-)
>
>diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
>index 641c07347e8d..8c6998920b2a 100644
>--- a/drivers/nvme/host/core.c
>+++ b/drivers/nvme/host/core.c
>@@ -1584,6 +1584,47 @@ static int nvme_ioctl(struct block_device *bdev, fmode_t mode,
> 	return ret;
> }
> 
>+#ifdef CONFIG_COMPAT
>+struct nvme_user_io32 {
>+	__u8	opcode;
>+	__u8	flags;
>+	__u16	control;
>+	__u16	nblocks;
>+	__u16	rsvd;
>+	__u64	metadata;
>+	__u64	addr;
>+	__u64	slba;
>+	__u32	dsmgmt;
>+	__u32	reftag;
>+	__u16	apptag;
>+	__u16	appmask;
>+} __attribute__((__packed__));
>+
>+#define NVME_IOCTL_SUBMIT_IO32	_IOW('N', 0x42, struct nvme_user_io32)
>+
>+static int nvme_compat_ioctl(struct block_device *bdev, fmode_t mode,
>+		unsigned int cmd, unsigned long arg)
>+{
>+	/*
>+	 * Corresponds to the difference of NVME_IOCTL_SUBMIT_IO
>+	 * between 32 bit programs and 64 bit kernel.
>+	 * The cause is that the results of sizeof(struct nvme_user_io),
>+	 * which is used to define NVME_IOCTL_SUBMIT_IO,
>+	 * are not same between 32 bit compiler and 64 bit compiler.
>+	 * NVME_IOCTL_SUBMIT_IO32 is for 64 bit kernel handling
>+	 * NVME_IOCTL_SUBMIT_IO issued from 32 bit programs.
>+	 * Other IOCTL numbers are same between 32 bit and 64 bit.
>+	 * So there is nothing to do regarding to other IOCTL numbers.
>+	 */
>+	if (cmd == NVME_IOCTL_SUBMIT_IO32)
>+		return nvme_ioctl(bdev, mode, NVME_IOCTL_SUBMIT_IO, arg);
>+
>+	return nvme_ioctl(bdev, mode, cmd, arg);
>+}
>+#else
>+#define nvme_compat_ioctl	NULL
>+#endif /* CONFIG_COMPAT */
>+
> static int nvme_open(struct block_device *bdev, fmode_t mode)
> {
> 	struct nvme_ns *ns = bdev->bd_disk->private_data;
>@@ -2027,7 +2068,7 @@ EXPORT_SYMBOL_GPL(nvme_sec_submit);
> static const struct block_device_operations nvme_fops = {
> 	.owner		= THIS_MODULE,
> 	.ioctl		= nvme_ioctl,
>-	.compat_ioctl	= nvme_ioctl,
>+	.compat_ioctl	= nvme_compat_ioctl,
> 	.open		= nvme_open,
> 	.release	= nvme_release,
> 	.getgeo		= nvme_getgeo,
>@@ -2055,7 +2096,7 @@ const struct block_device_operations nvme_ns_head_ops = {
> 	.open		= nvme_ns_head_open,
> 	.release	= nvme_ns_head_release,
> 	.ioctl		= nvme_ioctl,
>-	.compat_ioctl	= nvme_ioctl,
>+	.compat_ioctl	= nvme_compat_ioctl,
> 	.getgeo		= nvme_getgeo,
> 	.pr_ops		= &nvme_pr_ops,
> };
>-- 
>2.20.1
>
>
>