linux-kernel - [PATCH 6/6] ipc/util.c: correct comment in ipc_obtain_object

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Message-Id: <20180705055920.19611-7-manfred@colorfullife.com>
Date:   Thu,  5 Jul 2018 07:59:20 +0200
From:   Manfred Spraul <manfred@...orfullife.com>
To:     LKML <linux-kernel@...r.kernel.org>,
        Davidlohr Bueso <dave@...olabs.net>,
        Dmitry Vyukov <dvyukov@...gle.com>
Cc:     1vier1@....de, Andrew Morton <akpm@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        Manfred Spraul <manfred@...orfullife.com>
Subject: [PATCH 6/6] ipc/util.c: correct comment in ipc_obtain_object_check

The comment that explains ipc_obtain_object_check is wrong:
The function checks the sequence number, not the reference
counter.
Note that checking the reference counter would be meaningless:
The reference counter is decreased without holding any locks,
thus an object with kern_ipc_perm.deleted=true may disappear at
the end of the next rcu grace period.

Signed-off-by: Manfred Spraul <manfred@...orfullife.com>
---
 ipc/util.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/ipc/util.c b/ipc/util.c
index 4f2db913acf9..776a9ce2905f 100644
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -646,8 +646,8 @@ struct kern_ipc_perm *ipc_lock_idr(struct ipc_ids *ids, int id)
  * @ids: ipc identifier set
  * @id: ipc id to look for
  *
- * Similar to ipc_obtain_object_idr() but also checks
- * the ipc object reference counter.
+ * Similar to ipc_obtain_object_idr() but also checks the ipc object
+ * sequence number.
  *
  * Call inside the RCU critical section.
  * The ipc object is *not* locked on exit.
-- 
2.17.1