[PATCH] posix: Only check shm_unlink obj_err if necessary

[Kinsey Moore]

Is there anything stopping this from being merged? I just ran into this bug again on the current project I'm working on.

Kinsey

-----Original Message-----
From: Kinsey Moore <kinsey.moore at oarcorp.com> 
Sent: Tuesday, January 28, 2020 12:37
To: devel at rtems.org
Cc: Kinsey Moore <kinsey.moore at oarcorp.com>
Subject: [PATCH] posix: Only check shm_unlink obj_err if necessary

In the nominal case checked by spsysinit01, obj_err is unmodified if _POSIX_Shm_Get_by_name returns non-NULL. In the case of shm_unlink, this means an uninitialized value is passed into the switch and it appears this test was passing by virtue of the stack having the right value on it in most cases. This now checks obj_err only if _POSIX_Shm_Get_by_name returns NULL.
---
 cpukit/posix/src/shmunlink.c | 45 ++++++++++++++++++------------------
 1 file changed, 23 insertions(+), 22 deletions(-)

diff --git a/cpukit/posix/src/shmunlink.c b/cpukit/posix/src/shmunlink.c index 00d743ac80..39c2ba0d87 100644
--- a/cpukit/posix/src/shmunlink.c
+++ b/cpukit/posix/src/shmunlink.c
@@ -29,28 +29,29 @@ int shm_unlink( const char *name )
   _Objects_Allocator_lock();
 
   shm = _POSIX_Shm_Get_by_name( name, 0, &obj_err );
-  switch ( obj_err ) {
-    case OBJECTS_GET_BY_NAME_INVALID_NAME:
-      err = ENOENT;
-      break;
-
-    case OBJECTS_GET_BY_NAME_NAME_TOO_LONG:
-      err = ENAMETOOLONG;
-      break;
-
-    case OBJECTS_GET_BY_NAME_NO_OBJECT:
-    default:
-      _Objects_Namespace_remove_string(
-        &_POSIX_Shm_Information,
-        &shm->Object
-      );
-
-      if ( shm->reference_count == 0 ) {
-        /* Only remove the shm object if no references exist to it. Otherwise,
-         * the shm object will be freed later in _POSIX_Shm_Attempt_delete */
-        _POSIX_Shm_Free( shm );
-      }
-      break;
+  if ( shm ) {
+    _Objects_Namespace_remove_string(
+      &_POSIX_Shm_Information,
+      &shm->Object
+    );
+
+    if ( shm->reference_count == 0 ) {
+      /* Only remove the shm object if no references exist to it. Otherwise,
+       * the shm object will be freed later in _POSIX_Shm_Attempt_delete */
+      _POSIX_Shm_Free( shm );
+    }
+  } else {
+    switch ( obj_err ) {
+      case OBJECTS_GET_BY_NAME_NAME_TOO_LONG:
+        err = ENAMETOOLONG;
+        break;
+
+      case OBJECTS_GET_BY_NAME_INVALID_NAME:
+      case OBJECTS_GET_BY_NAME_NO_OBJECT:
+      default:
+        err = ENOENT;
+        break;
+    }
   }
 
   _Objects_Allocator_unlock();
--
2.20.1