From 66470b18179f8839a62b4c20ffd3903a4025fe90 Mon Sep 17 00:00:00 2001
From: Kees Cook <keescook@chromium.org>
Date: Wed, 12 Jul 2017 14:34:53 -0700
Subject: [PATCH 06/20] ipc/shm: do not use ipc_rcu_free()
Git-commit: 66470b18179f8839a62b4c20ffd3903a4025fe90
Patch-mainline: v4.13-rc1
References: bsc#1050323

Avoid using ipc_rcu_free, since it just re-finds the original structure
pointer.  For the pre-list-init failure path, there is no RCU needed,
since it was just allocated.  It can be directly freed.

Link: http://lkml.kernel.org/r/20170525185107.12869-7-manfred@colorfullife.com
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>

---
 ipc/shm.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/ipc/shm.c b/ipc/shm.c
index 5ef6d31a52c5..566c1e193ee1 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -172,6 +172,11 @@ static inline void shm_lock_by_ptr(struct shmid_kernel *ipcp)
 	ipc_lock_object(&ipcp->shm_perm);
 }
 
+static void __shm_free(struct shmid_kernel *shp)
+{
+	kvfree(shp);
+}
+
 static void shm_rcu_free(struct rcu_head *head)
 {
 	struct kern_ipc_perm *ptr = container_of(head, struct kern_ipc_perm,
@@ -179,7 +184,7 @@ static void shm_rcu_free(struct rcu_head *head)
 	struct shmid_kernel *shp = container_of(ptr, struct shmid_kernel,
 							shm_perm);
 	security_shm_free(shp);
-	ipc_rcu_free(head);
+	__shm_free(shp);
 }
 
 static inline void shm_rmid(struct ipc_namespace *ns, struct shmid_kernel *s)
@@ -557,7 +562,7 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params)
 	shp->shm_perm.security = NULL;
 	error = security_shm_alloc(shp);
 	if (error) {
-		ipc_rcu_putref(&shp->shm_perm, ipc_rcu_free);
+		__shm_free(shp);
 		return error;
 	}
 
-- 
2.12.0