From: Kees Cook <keescook@xxxxxxxxxxxx> Subject: ipc/sem: avoid ipc_rcu_alloc() 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@xxxxxxxxxxxxxxxx: Rediff, because the memset was temporarily inside ipc_rcu_alloc()] Link: http://lkml.kernel.org/r/20170525185107.12869-10-manfred@xxxxxxxxxxxxxxxx Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> Signed-off-by: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx> Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- ipc/sem.c | 25 ++++++++++++++++++++----- 1 file changed, 20 insertions(+), 5 deletions(-) diff -puN ipc/sem.c~ipc-sem-avoid-ipc_rcu_alloc ipc/sem.c --- a/ipc/sem.c~ipc-sem-avoid-ipc_rcu_alloc +++ a/ipc/sem.c @@ -451,6 +451,25 @@ static inline void sem_rmid(struct ipc_n 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 * 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 * 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; _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
