2005-12-23 22:57:53

by Manfred Spraul

[permalink] [raw]

Subject: [PATCH] add missing memory barriers to ipc/sem.c

---

--- 2.6/ipc/sem.c 2005-12-19 01:36:54.000000000 +0100
+++ build-2.6/ipc/sem.c 2005-12-23 23:25:17.000000000 +0100
@@ -381,6 +381,7 @@
/* hands-off: q will disappear immediately after
* writing q->status.
*/
+ smb_wmb();
q->status = error;
q = n;
} else {
@@ -461,6 +462,7 @@
n = q->next;
q->status = IN_WAKEUP;
wake_up_process(q->sleeper); /* doesn't sleep */
+ smp_wmb();
q->status = -EIDRM; /* hands-off q */
q = n;
}

---

Attachments:

patch-ipc-sem-wmb (465.00 B)

2005-12-24 11:38:34

by Thomas Backlund

[permalink] [raw]

Subject: Re: [PATCH] add missing memory barriers to ipc/sem.c

---

Manfred Spraul wrote:
> Hi Linus,
>
> Two smp_wmb() statements are missing in the sysv sem code: This could
> cause stack corruptions.
> The attached patch adds them.
>
> Signed-Off-By: Manfred Spraul <[email protected]>
>
>
> ------------------------------------------------------------------------
>
> --- 2.6/ipc/sem.c 2005-12-19 01:36:54.000000000 +0100
> +++ build-2.6/ipc/sem.c 2005-12-23 23:25:17.000000000 +0100
> @@ -381,6 +381,7 @@
> /* hands-off: q will disappear immediately after
> * writing q->status.
> */
> + smb_wmb();

Typo? Shouldn't it be smp_wmb();

> q->status = error;
> q = n;
> } else {
> @@ -461,6 +462,7 @@
> n = q->next;
> q->status = IN_WAKEUP;
> wake_up_process(q->sleeper); /* doesn't sleep */
> + smp_wmb();
> q->status = -EIDRM; /* hands-off q */
> q = n;
> }