linux-kernel - [PATCH] lguest: make sure cpu is initialized before accessing it

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Message-ID: <20080209155317.GA12841@kernel.sg>
Date:	Sat, 9 Feb 2008 23:53:17 +0800
From:	Eugene Teo <eugeneteo@...nel.sg>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	linux-kernel@...r.kernel.org, lguest@...abs.org
Subject: [PATCH] lguest: make sure cpu is initialized before accessing it

If req is LHREQ_INITIALIZE, and the guest has been initialized before
(unlikely), it will attempt to access cpu->tsk even though cpu is not yet
initialized.

Signed-off-by: Eugene Teo <eugeneteo@...nel.sg>
---
 drivers/lguest/lguest_user.c |   14 +++++++-------
 1 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/lguest/lguest_user.c b/drivers/lguest/lguest_user.c
index 85d42d3..9cbb285 100644
--- a/drivers/lguest/lguest_user.c
+++ b/drivers/lguest/lguest_user.c
@@ -241,15 +241,15 @@ static ssize_t write(struct file *file, const char __user *in,
 		cpu = &lg->cpus[cpu_id];
 		if (!cpu)
 			return -EINVAL;
-	}
 
-	/* Once the Guest is dead, all you can do is read() why it died. */
-	if (lg && lg->dead)
-		return -ENOENT;
+		/* Once the Guest is dead, all you can do is read() why it died. */
+		if (lg && lg->dead)
+			return -ENOENT;
 
-	/* If you're not the task which owns the Guest, you can only break */
-	if (lg && current != cpu->tsk && req != LHREQ_BREAK)
-		return -EPERM;
+		/* If you're not the task which owns the Guest, you can only break */
+		if (lg && current != cpu->tsk && req != LHREQ_BREAK)
+			return -EPERM;
+	}
 
 	switch (req) {
 	case LHREQ_INITIALIZE:

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