Linux Virtualization - Dec 2011 - [PATCH 4/9] drivers/xen/gntalloc.c: introduce missing kfree

Error handling code following a kmalloc should free the allocated data.
Out_unlock is used on both success and failure, so free vm_priv before
jumping to that label.

A simplified version of the semantic match that finds the problem is as
follows: (http://coccinelle.lip6.fr)

// <smpl>
@r exists@
local idexpression x;
statement S;
identifier f1;
position p1,p2;
expression *ptr != NULL;
@@

x at p1 = \(kmalloc\|kzalloc\|kcalloc\)(...);
...
if (x == NULL) S
<... when != x
     when != if (...) { <+...x...+> }
x->f1
...>
(
 return \(0\|<+...x...+>\|ptr\);
|
 return at p2 ...;
)

@script:python@
p1 << r.p1;
p2 << r.p2;
@@

print "* file: %s kmalloc %s return %s" %
(p1[0].file,p1[0].line,p2[0].line)
// </smpl>

Signed-off-by: Julia Lawall <julia at diku.dk>

---
 drivers/xen/gntalloc.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/xen/gntalloc.c b/drivers/xen/gntalloc.c
index e2400c8..934985d 100644
--- a/drivers/xen/gntalloc.c
+++ b/drivers/xen/gntalloc.c
@@ -525,6 +525,7 @@ static int gntalloc_mmap(struct file *filp, struct
vm_area_struct *vma)
 		rv = -ENOENT;
 		pr_debug("%s: Could not find grant reference",
 				__func__);
+		kfree(vm_priv);
 		goto out_unlock;
 	}

On Fri, Dec 23, 2011 at 06:39:29PM +0100, Julia Lawall
wrote:
> Error handling code following a kmalloc should free the allocated data.
> Out_unlock is used on both success and failure, so free vm_priv before
> jumping to that label.
Applied. Thanks!