linux-kernel - [PATCH v2 1/2] lsm: Clarify documentation of vm_enough

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Date:   Mon, 28 Nov 2022 15:42:39 +0100
From:   Roberto Sassu <roberto.sassu@...weicloud.com>
To:     paul@...l-moore.com, casey@...aufler-ca.com, omosnace@...hat.com,
        john.johansen@...onical.com, kpsingh@...nel.org
Cc:     bpf@...r.kernel.org, linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Roberto Sassu <roberto.sassu@...wei.com>
Subject: [PATCH v2 1/2] 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 if all LSMs return a positive value
__vm_enough_memory() will be called with cap_sys_admin set. If at least one
LSM returns 0 or negative, it will be called with cap_sys_admin cleared.

Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
---
 include/linux/lsm_hooks.h | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 2831efebde69..c35e260efd8c 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1398,7 +1398,11 @@
  *	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 the LSM infrastructure to the
+ *	caller. If all LSMs return a positive value, __vm_enough_memory() will
+ *	be called with cap_sys_admin set. If at least one LSM returns 0 or
+ *	negative, __vm_enough_memory() will be called with cap_sys_admin
+ *	cleared.
  *
  * @ismaclabel:
  *	Check if the extended attribute specified by @name
-- 
2.25.1