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Message-Id: <20170525185107.12869-10-manfred@colorfullife.com>
Date: Thu, 25 May 2017 20:50:56 +0200
From: Manfred Spraul <manfred@...orfullife.com>
To: mtk.manpages@...il.com, Andrew Morton <akpm@...ux-foundation.org>,
Kees Cook <keescook@...omium.org>
Cc: LKML <linux-kernel@...r.kernel.org>, 1vier1@....de,
Davidlohr Bueso <dave@...olabs.net>, mingo@...nel.org,
peterz@...radead.org, fabf@...net.be,
Manfred Spraul <manfred@...orfullife.com>
Subject: [PATCH 09/20] ipc/sem: Avoid ipc_rcu_alloc()
From: Kees Cook <keescook@...omium.org>
Instead of using ipc_rcu_alloc() which only performs the refcount
bump, open code it to perform better sem-specific checks. This
also allows for sem_array structure layout to be randomized in the
future.
Signed-off-by: Kees Cook <keescook@...omium.org>
[manfred@...orfullife.com: Rediff, because the memset was
temporarily inside ipc_rcu_alloc()]
Signed-off-by: Manfred Spraul <manfred@...orfullife.com>
---
ipc/sem.c | 25 ++++++++++++++++++++-----
1 file changed, 20 insertions(+), 5 deletions(-)
diff --git a/ipc/sem.c b/ipc/sem.c
index a04c4d6..445a5b5 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -451,6 +451,25 @@ static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
ipc_rmid(&sem_ids(ns), &s->sem_perm);
}
+static struct sem_array *sem_alloc(size_t nsems)
+{
+ struct sem_array *sma;
+ size_t size;
+
+ if (nsems > (INT_MAX - sizeof(*sma)) / sizeof(sma->sems[0]))
+ return NULL;
+
+ size = sizeof(*sma) + nsems * sizeof(sma->sems[0]);
+ sma = kvmalloc(size, GFP_KERNEL);
+ if (unlikely(!sma))
+ return NULL;
+
+ memset(sma, 0, size);
+ atomic_set(&sma->sem_perm.refcount, 1);
+
+ return sma;
+}
+
/**
* newary - Create a new semaphore set
* @ns: namespace
@@ -463,7 +482,6 @@ static int newary(struct ipc_namespace *ns, struct ipc_params *params)
int id;
int retval;
struct sem_array *sma;
- int size;
key_t key = params->key;
int nsems = params->u.nsems;
int semflg = params->flg;
@@ -474,10 +492,7 @@ static int newary(struct ipc_namespace *ns, struct ipc_params *params)
if (ns->used_sems + nsems > ns->sc_semmns)
return -ENOSPC;
- BUILD_BUG_ON(offsetof(struct sem_array, sem_perm) != 0);
-
- size = sizeof(*sma) + nsems * sizeof(sma->sems[0]);
- sma = container_of(ipc_rcu_alloc(size), struct sem_array, sem_perm);
+ sma = sem_alloc(nsems);
if (!sma)
return -ENOMEM;
--
2.9.3
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