From: Kees Cook <[email protected]> Instead of using ipc_rcu_alloc() which only performs the refcount bump, open code it. This also allows for shmid_kernel structure layout to be randomized in the future.
Signed-off-by: Kees Cook <[email protected]> Signed-off-by: Manfred Spraul <[email protected]> --- ipc/shm.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) diff --git a/ipc/shm.c b/ipc/shm.c index 77e1bff..c9f1f30 100644 --- a/ipc/shm.c +++ b/ipc/shm.c @@ -518,6 +518,19 @@ static const struct vm_operations_struct shm_vm_ops = { #endif }; +static struct shmid_kernel *shm_alloc(void) +{ + struct shmid_kernel *shp; + + shp = kvmalloc(sizeof(*shp), GFP_KERNEL); + if (unlikely(!shp)) + return NULL; + + atomic_set(&shp->shm_perm.refcount, 1); + + return shp; +} + /** * newseg - Create a new shared memory segment * @ns: namespace @@ -548,10 +561,7 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params) ns->shm_tot + numpages > ns->shm_ctlall) return -ENOSPC; - BUILD_BUG_ON(offsetof(struct shmid_kernel, shm_perm) != 0); - - shp = container_of(ipc_rcu_alloc(sizeof(*shp)), struct shmid_kernel, - shm_perm); + shp = shm_alloc(); if (!shp) return -ENOMEM; -- 2.9.3
