From 2ec55f8024db859d70f14c26e91ca044328dd50d Mon Sep 17 00:00:00 2001
From: Manfred Spraul <manfred@colorfullife.com>
Date: Wed, 12 Jul 2017 14:35:13 -0700
Subject: [PATCH] ipc/sem.c: avoid ipc_rcu_putref for failed ipc_addid()
Loosely based on a patch from Kees Cook <keescook@chromium.org>:
- id and retval can be merged
- if ipc_addid() fails, then use call_rcu() directly.
The difference is that call_rcu is used for failed ipc_addid() calls, to
continue to guaranteed an rcu delay for security_sem_free().
Link: http://lkml.kernel.org/r/20170525185107.12869-14-manfred@colorfullife.com
Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
ipc/sem.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)
diff --git a/ipc/sem.c b/ipc/sem.c
index 445a5b5eb88fd..2b2ed56e0fde2 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -479,7 +479,6 @@ static struct sem_array *sem_alloc(size_t nsems)
*/
static int newary(struct ipc_namespace *ns, struct ipc_params *params)
{
- int id;
int retval;
struct sem_array *sma;
key_t key = params->key;
@@ -520,10 +519,10 @@ static int newary(struct ipc_namespace *ns, struct ipc_params *params)
sma->sem_nsems = nsems;
sma->sem_ctime = get_seconds();
- id = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
- if (id < 0) {
- ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
- return id;
+ retval = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
+ if (retval < 0) {
+ call_rcu(&sma->sem_perm.rcu, sem_rcu_free);
+ return retval;
}
ns->used_sems += nsems;
--
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