[PATCH 4.9 14/70] selinux: use GFP_NOWAIT in the AVC kmem_caches

Greg Kroah-Hartman
2018-09-17T22:58:14Z

From: Michal Hocko <mhocko@kernel.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@kernel.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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;