linux-kernel - [RFC][PATCH 1/4] lsm: Clarify documentation of vm_enough

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Message-Id: <20221115175652.3836811-2-roberto.sassu@huaweicloud.com>
Date:   Tue, 15 Nov 2022 18:56:49 +0100
From:   Roberto Sassu <roberto.sassu@...weicloud.com>
To:     ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
        martin.lau@...ux.dev, song@...nel.org, yhs@...com,
        john.fastabend@...il.com, kpsingh@...nel.org, sdf@...gle.com,
        haoluo@...gle.com, jolsa@...nel.org, revest@...omium.org,
        jackmanb@...omium.org, paul@...l-moore.com, jmorris@...ei.org,
        serge@...lyn.com
Cc:     bpf@...r.kernel.org, linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Roberto Sassu <roberto.sassu@...wei.com>
Subject: [RFC][PATCH 1/4] lsm: Clarify documentation of vm_enough_memory hook

From: Roberto Sassu <roberto.sassu@...wei.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@...wei.com>
Reviewed-by: KP Singh <kpsingh@...nel.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