[RFC][PATCH 1/4] lsm: Clarify documentation of vm_enough_memory hook

From: Roberto Sassu <roberto.sassu@huaweicloud.com>
To: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org,
	martin.lau@linux.dev, song@kernel.org, yhs@fb.com,
	john.fastabend@gmail.com, kpsingh@kernel.org, sdf@google.com,
	haoluo@google.com, jolsa@kernel.org, revest@chromium.org,
	jackmanb@chromium.org, paul@paul-moore.com, jmorris@namei.org,
	serge@hallyn.com
Cc: bpf@vger.kernel.org, linux-security-module@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Roberto Sassu <roberto.sassu@huawei.com>
Subject: [RFC][PATCH 1/4] lsm: Clarify documentation of vm_enough_memory hook
Date: Tue, 15 Nov 2022 18:56:49 +0100	[thread overview]
Message-ID: <20221115175652.3836811-2-roberto.sassu@huaweicloud.com> (raw)
In-Reply-To: <20221115175652.3836811-1-roberto.sassu@huaweicloud.com>

From: Roberto Sassu <roberto.sassu@huawei.com>

include/linux/lsm_hooks.h reports the result of the LSM infrastructure to
the callers, not what LSMs should return to the LSM infrastructure.

Clarify that and add that returning 1 from the LSMs means calling
__vm_enough_memory() with cap_sys_admin set, 0 without.

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Reviewed-by: KP Singh <kpsingh@kernel.org>
---
 include/linux/lsm_hooks.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 4ec80b96c22e..f40b82ca91e7 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1411,7 +1411,9 @@
  *	Check permissions for allocating a new virtual mapping.
  *	@mm contains the mm struct it is being added to.
  *	@pages contains the number of pages.
- *	Return 0 if permission is granted.
+ *	Return 0 if permission is granted by LSMs to the caller. LSMs should
+ *	return 1 if __vm_enough_memory() should be called with
+ *	cap_sys_admin set, 0 if not.
  *
  * @ismaclabel:
  *	Check if the extended attribute specified by @name
-- 
2.25.1

