MIPS: VPE loader: Check vmalloc return value in vpe_open

The return value of the vmalloc() call in arch/mips/kernel/vpe.c::vpe_open()
is not checked, so we potentially store a null pointer in v->pbuffer.  Add
a check for a null return and then return -ENOMEM in that case.

[Ralf: The check added by Jesper's original patch is where it logically
should be.  Adding it eleminated the need for the checks in a few other
places, so I removed them.  There still is a zillion of other things that
need to be fixed in this file / API.]

Signed-off-by: Jesper Juhl <jj@chaosbits.net>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/1747/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/vpe.c

@@ -1092,6 +1092,10 @@ static int vpe_open(struct inode *inode, struct file *filp)
 
 	/* this of-course trashes what was there before... */
 	v->pbuffer = vmalloc(P_SIZE);
+	if (!v->pbuffer) {
+		pr_warning("VPE loader: unable to allocate memory\n");
+		return -ENOMEM;
+	}
 	v->plen = P_SIZE;
 	v->load_addr = NULL;
 	v->len = 0;
@@ -1149,10 +1153,9 @@ static int vpe_release(struct inode *inode, struct file *filp)
 	if (ret < 0)
 		v->shared_ptr = NULL;
 
-	// cleanup any temp buffers
-	if (v->pbuffer)
-		vfree(v->pbuffer);
+	vfree(v->pbuffer);
 	v->plen = 0;
+
 	return ret;
 }
 
@@ -1169,11 +1172,6 @@ static ssize_t vpe_write(struct file *file, const char __user * buffer,
 	if (v == NULL)
 		return -ENODEV;
 
-	if (v->pbuffer == NULL) {
-		printk(KERN_ERR "VPE loader: no buffer for program\n");
-		return -ENOMEM;
-	}
-
 	if ((count + v->len) > v->plen) {
 		printk(KERN_WARNING
 		       "VPE loader: elf size too big. Perhaps strip uneeded symbols\n");