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ipc/sem: avoid ipc_rcu_alloc()

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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.

[manfred@colorfullife.com: Rediff, because the memset was temporarily inside ipc_rcu_alloc()]
Link: http://lkml.kernel.org/r/20170525185107.12869-10-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>
This commit is contained in:
Kees Cook 2017-07-12 14:35:02 -07:00 committed by Linus Torvalds
parent 5ccc8fb54f
commit 101ede01df
1 changed files with 20 additions and 5 deletions
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25
ipc/sem.c
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@ -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;