hardening: Move BUG_ON_DATA_CORRUPTION to hardening options

BUG_ON_DATA_CORRUPTION is turning detected corruptions of list data
structures from WARNings into BUGs. This can be useful to stop further
corruptions or even exploitation attempts.

However, the option has less to do with debugging than with hardening.
With the introduction of LIST_HARDENED, it makes more sense to move it
to the hardening options, where it selects LIST_HARDENED instead.

Without this change, combining BUG_ON_DATA_CORRUPTION with LIST_HARDENED
alone wouldn't be possible, because DEBUG_LIST would always be selected
by BUG_ON_DATA_CORRUPTION.
Signed-off-by: Marco Elver <elver@google.com>
Link: https://lore.kernel.org/r/20230811151847.1594958-4-elver@google.comSigned-off-by: Kees Cook <keescook@chromium.org>

lib/Kconfig.debug

@@ -1673,7 +1673,7 @@ menu "Debug kernel data structures"
 
 config DEBUG_LIST
 	bool "Debug linked list manipulation"
-	depends on DEBUG_KERNEL || BUG_ON_DATA_CORRUPTION
+	depends on DEBUG_KERNEL
 	select LIST_HARDENED
 	help
 	  Enable this to turn on extended checks in the linked-list walking
@@ -1715,16 +1715,6 @@ config DEBUG_NOTIFIERS
 	  This is a relatively cheap check but if you care about maximum
 	  performance, say N.
 
-config BUG_ON_DATA_CORRUPTION
-	bool "Trigger a BUG when data corruption is detected"
-	select DEBUG_LIST
-	help
-	  Select this option if the kernel should BUG when it encounters
-	  data corruption in kernel memory structures when they get checked
-	  for validity.
-
-	  If unsure, say N.
-
 config DEBUG_MAPLE_TREE
 	bool "Debug maple trees"
 	depends on DEBUG_KERNEL

security/Kconfig.hardening

@@ -290,6 +290,16 @@ config LIST_HARDENED
 
 	  If unsure, say N.
 
+config BUG_ON_DATA_CORRUPTION
+	bool "Trigger a BUG when data corruption is detected"
+	select LIST_HARDENED
+	help
+	  Select this option if the kernel should BUG when it encounters
+	  data corruption in kernel memory structures when they get checked
+	  for validity.
+
+	  If unsure, say N.
+
 endmenu
 
 config CC_HAS_RANDSTRUCT