auxv_up() quit at AT_NULL, especially when AT_BASE has been omitted.

Based on contribution from Brian Geffon 'bgaff'
https://github.com/upx/upx/pull/215 ; bgaff
	modified:   amd64-linux.elf-main.c
	modified:   i386-bsd.elf-main.c
	modified:   i386-linux.elf.interp-main.c
	modified:   i386-openbsd.elf-main.c

src/stub/src/amd64-linux.elf-main.c

@@ -350,6 +350,11 @@ auxv_up(Elf64_auxv_t *av, unsigned const type, uint64_t const value)
             av->a_un.a_val = value;
             return;
         }
+        if (av->a_type==AT_NULL) {
+            // We can't do this as part of the for loop because we overwrite
+            // AT_NULL too.
+            return;
+        }
     }
 }
 

src/stub/src/i386-bsd.elf-main.c

@@ -352,6 +352,11 @@ auxv_up(Elf32_auxv_t *av, unsigned const type, unsigned const value)
             av->a_un.a_val = value;
             return;
         }
+        if (av->a_type==AT_NULL) {
+            // We can't do this as part of the for loop because we overwrite
+            // AT_NULL too.
+            return;
+        }
     }
 }
 

src/stub/src/i386-linux.elf.interp-main.c

@@ -223,6 +223,11 @@ auxv_up(Elf32_auxv_t *av, unsigned const type, unsigned const value)
             av->a_un.a_val = value;
             return;
         }
+        if (av->a_type==AT_NULL) {
+            // We can't do this as part of the for loop because we overwrite
+            // AT_NULL too.
+            return;
+        }
     }
 }
 

src/stub/src/i386-openbsd.elf-main.c

@@ -346,6 +346,11 @@ auxv_up(Elf32_auxv_t *av, unsigned const type, unsigned const value)
             av->a_un.a_val = value;
             return;
         }
+        if (av->a_type==AT_NULL) {
+            // We can't do this as part of the for loop because we overwrite
+            // AT_NULL too.
+            return;
+        }
     }
 }