linux-kernel - [PATCH RESEND v3] nsfs: add compat ioctl handler

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Message-Id: <20221214-nsfs-ioctl-compat-v3-1-dce2d26e1fec@weissschuh.net>
Date:   Wed, 11 Jan 2023 16:46:30 +0000
From:   Thomas Weißschuh <linux@...ssschuh.net>
To:     Alexander Viro <viro@...iv.linux.org.uk>,
        Andrey Vagin <avagin@...nvz.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Serge Hallyn <serge@...lyn.com>
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Karel Zak <kzak@...hat.com>,
        Thomas Weißschuh <linux@...ssschuh.net>
Subject: [PATCH RESEND v3] nsfs: add compat ioctl handler

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 via compat_ptr_ioctl().

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@...hat.com>
Link: https://github.com/util-linux/util-linux/pull/1924#issuecomment-1344133656
Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
---
Changes in v3:
- Resend without changes
  v1 and v2 did not reach the mailing lists due to an issue in my mail setup
- Link to v2: https://lore.kernel.org/r/20221214-nsfs-ioctl-compat-v2-0-b295bb3913f6@weissschuh.net

Changes in v2:
- Use compat_ptr_ioctl()
- Link to v1: https://lore.kernel.org/r/20221214-nsfs-ioctl-compat-v1-0-b169796000b2@weissschuh.net
---
 fs/nsfs.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/nsfs.c b/fs/nsfs.c
index 3506f6074288..c28f69edef97 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   = compat_ptr_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@...ssschuh.net>