linux-kernel - [RFC PATCH] landlock: fix minimal required size for landlock_ruleset

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Date: Tue,  2 Jul 2024 17:47:45 +0800
From: Li Wang <liwang@...hat.com>
To: mic@...ikod.net,
	gnoack@...gle.com,
	paul@...l-moore.com
Cc: linux-kernel@...r.kernel.org,
	ltp@...ts.linux.it,
	Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
Subject: [RFC PATCH] landlock: fix minimal required size for landlock_ruleset_attr copying

As kernel commit fff69fb03dde ("landlock: Support network rules with TCP bind and connect")
introducing a new field 'handled_access_net' in the structure landlock_ruleset_attr,
but in the landlock_create_ruleset() it still uses the first field 'handled_access_fs'
to calculate minimal size, so that made decrease 1 is useless in LTP landlock01.c to
test the too-small-size.

Test code:
   rule_small_size = sizeof(struct landlock_ruleset_attr) - 1;
   tst_syscall(__NR_landlock_create_ruleset, ..., rule_small_size, 0)

Result:
  landlock01.c:49: TFAIL: Size is too small expected EINVAL: ENOMSG (42)

Signed-off-by: Li Wang <liwang@...hat.com>
Cc: Mickaël Salaün <mic@...ikod.net>
Cc: Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
Cc: Paul Moore <paul@...l-moore.com>
---

Notes:
    Hi Mickael,
       I'm not quite sure if that is on purpose to use the first field or kernel
       bug, can you take a look?

 security/landlock/syscalls.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
index 03b470f5a85a..f3cd7def7624 100644
--- a/security/landlock/syscalls.c
+++ b/security/landlock/syscalls.c
@@ -198,7 +198,7 @@ SYSCALL_DEFINE3(landlock_create_ruleset,
 	/* Copies raw user space buffer. */
 	err = copy_min_struct_from_user(&ruleset_attr, sizeof(ruleset_attr),
 					offsetofend(typeof(ruleset_attr),
-						    handled_access_fs),
+						    handled_access_net),
 					attr, size);
 	if (err)
 		return err;
-- 
2.45.2