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Re: [lvm-devel] [PATCH] libdm: Fix memory corruption if dm_asprintf fails.

Dne 18.10.2013 02:31, Mikulas Patocka napsal(a):
I found this bug when reading through my lvm changes.

We must set the variable dmt->geometry to NULL after freeing it.

dm_asprintf may fail, on failure it may not set dmt->geometry, thus
dmt->geometry would be pointing to a free string.

Signed-off-by: Mikulas Patocka <mpatocka redhat com>

  libdm/ioctl/libdm-iface.c |    1 +
  1 file changed, 1 insertion(+)

Index: lvm2-copy/libdm/ioctl/libdm-iface.c
--- lvm2-copy.orig/libdm/ioctl/libdm-iface.c	2013-10-18 02:26:07.000000000 +0200
+++ lvm2-copy/libdm/ioctl/libdm-iface.c	2013-10-18 02:26:16.000000000 +0200
@@ -817,6 +817,7 @@ int dm_task_set_geometry(struct dm_task
  			 const char *sectors, const char *start)
+	dmt->geometry = NULL;
  	if (dm_asprintf(&(dmt->geometry), "%s %s %s %s",
  			cylinders, heads, sectors, start) < 0) {


dm_asprintf() ->  dm_vasprintf() ->  first thing it does is:  *result = 0;

So it should never return failure and leave &dmt->geometry in undefined state. On error path it should always be set to NULL - unless there is a bug
in  dm_vasprintf() which would need to be fixed.


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