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Re: [libvirt] [PATCH] locking: avoid dereferencing a NULL pointer



On 09/21/2011 12:10 PM, ajia redhat com wrote:
From: Alex Jia<ajia redhat com>

* src/locking/lock_driver_sanlock.c: in fact, virStrcpy calls
   virStrncpy(dest, src, strlen(src), destbytes) then return result,
   if 'path' is NULL, it means 'src' is also NULL, strlen(NULL) will
   dereference a NULL pointer, which probably causes a segmentation fault.

Signed-off-by: Alex Jia<ajia redhat com>
---
  src/locking/lock_driver_sanlock.c |    2 +-
  1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/src/locking/lock_driver_sanlock.c b/src/locking/lock_driver_sanlock.c
index 2d72510..8c6d873 100644
--- a/src/locking/lock_driver_sanlock.c
+++ b/src/locking/lock_driver_sanlock.c
@@ -158,7 +158,7 @@ static int virLockManagerSanlockSetupLockspace(void)
      memcpy(ls.name, VIR_LOCK_MANAGER_SANLOCK_AUTO_DISK_LOCKSPACE, SANLK_NAME_LEN);
      ls.host_id = 0; /* Doesn't matter for initialization */
      ls.flags = 0;
-    if (!virStrcpy(ls.host_id_disk.path, path, SANLK_PATH_LEN)) {
+    if (!path || !virStrcpy(ls.host_id_disk.path, path, SANLK_PATH_LEN)) {
          virLockError(VIR_ERR_INTERNAL_ERROR,
                       _("Lockspace path '%s' exceeded %d characters"),
                       path, SANLK_PATH_LEN);

NACK. The prior virAsprintf guarantees that path is non-NULL at this point. Rather, the real problem that Coverity is complaining about here is that the only way to get to the error_unlink: label is if path is already non-NULL, so that the 'if (path)' in that label is redundant.

--
Eric Blake   eblake redhat com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org


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