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ipc/shm: avoid ipc_rcu_alloc() 

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.

Link: http://lkml.kernel.org/r/20170525185107.12869-11-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 14:35:05 -07:00 committed by Linus Torvalds
parent 101ede01df
commit 3e0c24042e
1 changed files with 14 additions and 4 deletions
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18
ipc/shm.c
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@ -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;