diff options
| author | Arjan van de Ven | 2008-08-15 15:29:38 -0700 |
|---|---|---|
| committer | Ingo Molnar | 2008-09-10 09:08:50 +0200 |
| commit | 1b2439dbb703ae8d95a9ce7ece6b7800b80f41f0 (patch) | |
| tree | 63c6c105b86ce45ca010dca4bd501a924afd05d1 | |
| parent | b09c3e3f1710b554348c98e78fbf4a661918779a (diff) | |
debug: add notifier chain debugging
during some development we suspected a case where we left something
in a notifier chain that was from a module that was unloaded already...
and that sort of thing is rather hard to track down.
This patch adds a very simple sanity check (which isn't all that
expensive) to make sure the notifier we're about to call is
actually from either the kernel itself of from a still-loaded
module, avoiding a hard-to-chase-down crash.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
| -rw-r--r-- | kernel/notifier.c | 16 | ||||
| -rw-r--r-- | lib/Kconfig.debug | 10 |
2 files changed, 26 insertions, 0 deletions
diff --git a/kernel/notifier.c b/kernel/notifier.c index 823be11584ef..143fdd77dbf7 100644 --- a/kernel/notifier.c +++ b/kernel/notifier.c @@ -21,6 +21,10 @@ BLOCKING_NOTIFIER_HEAD(reboot_notifier_list); static int notifier_chain_register(struct notifier_block **nl, struct notifier_block *n) { + if (!kernel_text_address((unsigned long)n->notifier_call)) { + WARN(1, "Invalid notifier registered!"); + return 0; + } while ((*nl) != NULL) { if (n->priority > (*nl)->priority) break; @@ -34,6 +38,10 @@ static int notifier_chain_register(struct notifier_block **nl, static int notifier_chain_cond_register(struct notifier_block **nl, struct notifier_block *n) { + if (!kernel_text_address((unsigned long)n->notifier_call)) { + WARN(1, "Invalid notifier registered!"); + return 0; + } while ((*nl) != NULL) { if ((*nl) == n) return 0; @@ -82,6 +90,14 @@ static int __kprobes notifier_call_chain(struct notifier_block **nl, while (nb && nr_to_call) { next_nb = rcu_dereference(nb->next); + +#ifdef CONFIG_DEBUG_NOTIFIERS + if (!kernel_text_address((unsigned long)nb->notifier_call)) { + WARN(1, "Invalid notifier called!"); + nb = next_nb; + continue; + } +#endif ret = nb->notifier_call(nb, val, v); if (nr_calls) diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 8b5a7d304a5f..342858fbabbc 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -536,6 +536,16 @@ config DEBUG_SG If unsure, say N. +config DEBUG_NOTIFIERS + bool "Debug notifier call chains" + depends on DEBUG_KERNEL + help + Enable this to turn on sanity checking for notifier call chains. + This is most useful for kernel developers to make sure that + modules properly unregister themselves from notifier chains. + This is a relatively cheap check but if you care about maximum + performance, say N. + config FRAME_POINTER bool "Compile the kernel with frame pointers" depends on DEBUG_KERNEL && \ |