[PATCH RESEND] nsfs: add compat ioctl handler

[Thomas Weißschuh]

As all parameters and return values of the ioctls have the same
representation on both 32bit and 64bit we can reuse the normal ioctl
handler for the compat handler.

All nsfs ioctls return a plain "int" filedescriptor which is a signed
4-byte integer type on both 32bit and 64bit.
The only parameter taken is by NS_GET_OWNER_UID and is a pointer to a
"uid_t" which is a 4-byte unsigned integer type on both 32bit and 64bit.

Fixes: 6786741dbf99 ("nsfs: add ioctl to get an owning user namespace for ns file descriptor")
Reported-By: Karel Zak <kzak@xxxxxxxxxx>
Signed-off-by: Thomas Weißschuh <linux@xxxxxxxxxxxxxx>
---
As all parameters and return values of the ioctls have the same
representation on both 32bit and 64bit we can reuse the normal ioctl
handler for the compat handler.

All nsfs ioctls return a plain "int" filedescriptor which is a signed
4-byte integer type on both 32bit and 64bit.
The only parameter taken is by NS_GET_OWNER_UID and is a pointer to a
"uid_t" which is a 4-byte unsigned integer type on both 32bit and 64bit.
---
To: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
To: Andrey Vagin <avagin@xxxxxxxxxx>
To: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
To: Serge Hallyn <serge@xxxxxxxxxx>
Cc: linux-fsdevel@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: Karel Zak <kzak@xxxxxxxxxx>
---
 fs/nsfs.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/nsfs.c b/fs/nsfs.c
index 3506f6074288..4d2644507364 100644
--- a/fs/nsfs.c
+++ b/fs/nsfs.c
@@ -21,6 +21,7 @@ static long ns_ioctl(struct file *filp, unsigned int ioctl,
 static const struct file_operations ns_file_operations = {
 	.llseek		= no_llseek,
 	.unlocked_ioctl = ns_ioctl,
+	.compat_ioctl   = ns_ioctl,
 };
 
 static char *ns_dname(struct dentry *dentry, char *buffer, int buflen)

---
base-commit: f9ff5644bcc04221bae56f922122f2b7f5d24d62
change-id: 20221214-nsfs-ioctl-compat-1548bf6581a7

Best regards,
-- 
Thomas Weißschuh <linux@xxxxxxxxxxxxxx>