From a2642f8770993a1598500bb6a8082b7c32faff8b Mon Sep 17 00:00:00 2001 From: Manfred Spraul Date: Wed, 12 Jul 2017 14:35:16 -0700 Subject: [PATCH] ipc/shm.c: avoid ipc_rcu_putref for failed ipc_addid() Loosely based on a patch from Kees Cook : - id and error can be merged - if operations before ipc_addid() fail, then use call_rcu() directly. The difference is that call_rcu is used for failures after security_shm_alloc(), to continue to guaranteed an rcu delay for security_sem_free(). Link: http://lkml.kernel.org/r/20170525185107.12869-15-manfred@colorfullife.com Signed-off-by: Manfred Spraul Cc: Kees Cook Cc: Davidlohr Bueso Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- ipc/shm.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) diff --git a/ipc/shm.c b/ipc/shm.c index 2ac489ef56e4..c5976d318ed1 100644 --- a/ipc/shm.c +++ b/ipc/shm.c @@ -548,7 +548,6 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params) size_t numpages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT; struct file *file; char name[13]; - int id; vm_flags_t acctflag = 0; if (size < SHMMIN || size > ns->shm_ctlmax) @@ -617,11 +616,9 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params) shp->shm_file = file; shp->shm_creator = current; - id = ipc_addid(&shm_ids(ns), &shp->shm_perm, ns->shm_ctlmni); - if (id < 0) { - error = id; + error = ipc_addid(&shm_ids(ns), &shp->shm_perm, ns->shm_ctlmni); + if (error < 0) goto no_id; - } list_add(&shp->shm_clist, ¤t->sysvshm.shm_clist); @@ -643,7 +640,7 @@ no_id: user_shm_unlock(size, shp->mlock_user); fput(file); no_file: - ipc_rcu_putref(&shp->shm_perm, shm_rcu_free); + call_rcu(&shp->shm_perm.rcu, shm_rcu_free); return error; } -- 2.20.1