linux-kernel - [PATCH v2] fs/proc/proc_sysctl.c: always initialize i_uid/i

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Message-Id: <20240322-sysctl-net-ownership-v2-1-a8b4a3306542@weissschuh.net>
Date: Fri, 22 Mar 2024 20:51:11 +0100
From: Thomas Weißschuh <linux@...ssschuh.net>
To: "David S. Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>, 
 Dmitry Torokhov <dmitry.torokhov@...il.com>, 
 "Eric W. Biederman" <ebiederm@...ssion.com>, 
 Joel Granados <j.granados@...sung.com>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Luis Chamberlain <mcgrof@...nel.org>, Kuniyuki Iwashima <kuniyu@...zon.com>, 
 stable@...r.kernel.org, 
 Thomas Weißschuh <linux@...ssschuh.net>
Subject: [PATCH v2] fs/proc/proc_sysctl.c: always initialize i_uid/i_gid

Commit e79c6a4fc923 ("net: make net namespace sysctls belong to container's owner")
added default values for i_uid/i_gid.
These however are only used when ctl_table_root->set_ownership is not
implemented.
But the callbacks themselves could fail to compute i_uid/i_gid and they
all need to have the same fallback logic for this case.

This is unnecessary code duplication and prone to errors.
For example net_ctl_set_ownership() missed the fallback.

Instead always initialize i_uid/i_gid inside the sysfs core so
set_ownership() can safely skip setting them.

Fixes: e79c6a4fc923 ("net: make net namespace sysctls belong to container's owner")
Cc: stable@...r.kernel.org
Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
---
Changes in v2:
- Move the fallback logic to the sysctl core
- Link to v1: https://lore.kernel.org/r/20240315-sysctl-net-ownership-v1-1-2b465555a292@weissschuh.net
---
 fs/proc/proc_sysctl.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index 37cde0efee57..9e34ab9c21e4 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -479,12 +479,10 @@ static struct inode *proc_sys_make_inode(struct super_block *sb,
 			make_empty_dir_inode(inode);
 	}

+	inode->i_uid = GLOBAL_ROOT_UID;
+	inode->i_gid = GLOBAL_ROOT_GID;
 	if (root->set_ownership)
 		root->set_ownership(head, table, &inode->i_uid, &inode->i_gid);
-	else {
-		inode->i_uid = GLOBAL_ROOT_UID;
-		inode->i_gid = GLOBAL_ROOT_GID;
-	}

 	return inode;
 }

---
base-commit: ff9c18e435b042596c9d48badac7488e3fa76a55
change-id: 20240315-sysctl-net-ownership-bc4e17eaeea6

Best regards,
-- 
Thomas Weißschuh <linux@...ssschuh.net>