linux-kernel - [PATCH 4.4 11/56] selinux: use GFP_NOWAIT in the AVC kmem

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Message-Id: <20180917213828.433882553@linuxfoundation.org>
Date:   Tue, 18 Sep 2018 00:41:44 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Michal Hocko <mhocko@...nel.org>,
        Mel Gorman <mgorman@...e.de>, Paul Moore <paul@...l-moore.com>,
        Amit Pundir <amit.pundir@...aro.org>
Subject: [PATCH 4.4 11/56] selinux: use GFP_NOWAIT in the AVC kmem_caches

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Michal Hocko <mhocko@...nel.org>

commit 476accbe2f6ef69caeebe99f52a286e12ac35aee upstream.

There is a strange __GFP_NOMEMALLOC usage pattern in SELinux,
specifically GFP_ATOMIC | __GFP_NOMEMALLOC which doesn't make much
sense.  GFP_ATOMIC on its own allows to access memory reserves while
__GFP_NOMEMALLOC dictates we cannot use memory reserves.  Replace this
with the much more sane GFP_NOWAIT in the AVC code as we can tolerate
memory allocation failures in that code.

Signed-off-by: Michal Hocko <mhocko@...nel.org>
Acked-by: Mel Gorman <mgorman@...e.de>
Signed-off-by: Paul Moore <paul@...l-moore.com>
Signed-off-by: Amit Pundir <amit.pundir@...aro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 security/selinux/avc.c |   14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

--- a/security/selinux/avc.c
+++ b/security/selinux/avc.c
@@ -348,27 +348,26 @@ static struct avc_xperms_decision_node
 	struct avc_xperms_decision_node *xpd_node;
 	struct extended_perms_decision *xpd;
 
-	xpd_node = kmem_cache_zalloc(avc_xperms_decision_cachep,
-				GFP_ATOMIC | __GFP_NOMEMALLOC);
+	xpd_node = kmem_cache_zalloc(avc_xperms_decision_cachep, GFP_NOWAIT);
 	if (!xpd_node)
 		return NULL;
 
 	xpd = &xpd_node->xpd;
 	if (which & XPERMS_ALLOWED) {
 		xpd->allowed = kmem_cache_zalloc(avc_xperms_data_cachep,
-						GFP_ATOMIC | __GFP_NOMEMALLOC);
+						GFP_NOWAIT);
 		if (!xpd->allowed)
 			goto error;
 	}
 	if (which & XPERMS_AUDITALLOW) {
 		xpd->auditallow = kmem_cache_zalloc(avc_xperms_data_cachep,
-						GFP_ATOMIC | __GFP_NOMEMALLOC);
+						GFP_NOWAIT);
 		if (!xpd->auditallow)
 			goto error;
 	}
 	if (which & XPERMS_DONTAUDIT) {
 		xpd->dontaudit = kmem_cache_zalloc(avc_xperms_data_cachep,
-						GFP_ATOMIC | __GFP_NOMEMALLOC);
+						GFP_NOWAIT);
 		if (!xpd->dontaudit)
 			goto error;
 	}
@@ -396,8 +395,7 @@ static struct avc_xperms_node *avc_xperm
 {
 	struct avc_xperms_node *xp_node;
 
-	xp_node = kmem_cache_zalloc(avc_xperms_cachep,
-				GFP_ATOMIC|__GFP_NOMEMALLOC);
+	xp_node = kmem_cache_zalloc(avc_xperms_cachep, GFP_NOWAIT);
 	if (!xp_node)
 		return xp_node;
 	INIT_LIST_HEAD(&xp_node->xpd_head);
@@ -550,7 +548,7 @@ static struct avc_node *avc_alloc_node(v
 {
 	struct avc_node *node;
 
-	node = kmem_cache_zalloc(avc_node_cachep, GFP_ATOMIC|__GFP_NOMEMALLOC);
+	node = kmem_cache_zalloc(avc_node_cachep, GFP_NOWAIT);
 	if (!node)
 		goto out;