linux-kernel - [PATCH] IPC initialize shmmax and shmall from the current value not the default

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Date:	Sun, 04 May 2014 01:48:29 +0300
From:	Marian Marinov <mm@...com>
To:	akpm@...ux-foundation.org, davidlohr@...com,
	n-horiguchi@...jp.nec.com, Greg KH <gregkh@...uxfoundation.org>,
	manfred@...orfullife.com,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux Containers <containers@...ts.linux-foundation.org>
Subject: [PATCH] IPC initialize shmmax and shmall from the current value not
 the default

When we are creating new IPC namespace that should be cloned from the current namespace it is a good idea to copy the 
values of the current shmmax and shmall to the new namespace.

Copying the values of the init_ipc_ns would allow us to create new ipc namespaces with different values without granting 
them privileges to change those values.

Here is the proposed patch:

---
  ipc/shm.c | 9 +++++++--
  1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/ipc/shm.c b/ipc/shm.c
index 7a51443..b7a4728 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -74,8 +74,13 @@ static int sysvipc_shm_proc_show(struct seq_file *s, void *it);

  void shm_init_ns(struct ipc_namespace *ns)
  {
-       ns->shm_ctlmax = SHMMAX;
-       ns->shm_ctlall = SHMALL;
+       if (ns == &init_ipc_ns) {
+               ns->shm_ctlmax = SHMMAX;
+               ns->shm_ctlall = SHMALL;
+       } else {
+               ns->shm_ctlmax = init_ipc_ns.shm_ctlmax;
+               ns->shm_ctlall = init_ipc_ns.shm_ctlall;
+       }
         ns->shm_ctlmni = SHMMNI;
         ns->shm_rmid_forced = 0;
         ns->shm_tot = 0;
-- 
1.8.4

-- 
Marian Marinov
Founder & CEO of 1H Ltd.
Jabber/GTalk: hackman@...ber.org
ICQ: 7556201
Mobile: +359 886 660 270
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