The patch titled
kprobes: disable preempt for module_text_address() and kernel_text_address()
has been added to the -mm tree. Its filename is
kprobes-disable-preempt-for-module_text_address-and-kernel_text_address.patch
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out what to do about this
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: kprobes: disable preempt for module_text_address() and kernel_text_address()
From: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
__register_kprobe() can be preempted after checking probing address but
before module_text_address() or try_module_get(), and in this interval the
module can be unloaded. In that case, try_module_get(probed_mod) will
access to invalid address, or kprobe will probe invalid address.
This patch uses preempt_disable() to protect it and uses
__module_text_address() and __kernel_text_address().
Signed-off-by: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Ananth N Mavinakayanahalli <ananth@xxxxxxxxxx>
Cc: Hiroshi Shimamoto <h-shimamoto@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/kprobes.c | 21 ++++++++++++++++-----
1 file changed, 16 insertions(+), 5 deletions(-)
diff -puN kernel/kprobes.c~kprobes-disable-preempt-for-module_text_address-and-kernel_text_address kernel/kprobes.c
--- a/kernel/kprobes.c~kprobes-disable-preempt-for-module_text_address-and-kernel_text_address
+++ a/kernel/kprobes.c
@@ -613,30 +613,37 @@ static int __kprobes __register_kprobe(s
return -EINVAL;
p->addr = addr;
- if (!kernel_text_address((unsigned long) p->addr) ||
- in_kprobes_functions((unsigned long) p->addr))
+ preempt_disable();
+ if (!__kernel_text_address((unsigned long) p->addr) ||
+ in_kprobes_functions((unsigned long) p->addr)) {
+ preempt_enable();
return -EINVAL;
+ }
p->mod_refcounted = 0;
/*
* Check if are we probing a module.
*/
- probed_mod = module_text_address((unsigned long) p->addr);
+ probed_mod = __module_text_address((unsigned long) p->addr);
if (probed_mod) {
- struct module *calling_mod = module_text_address(called_from);
+ struct module *calling_mod;
+ calling_mod = __module_text_address(called_from);
/*
* We must allow modules to probe themself and in this case
* avoid incrementing the module refcount, so as to allow
* unloading of self probing modules.
*/
if (calling_mod && calling_mod != probed_mod) {
- if (unlikely(!try_module_get(probed_mod)))
+ if (unlikely(!try_module_get(probed_mod))) {
+ preempt_enable();
return -EINVAL;
+ }
p->mod_refcounted = 1;
} else
probed_mod = NULL;
}
+ preempt_enable();
p->nmissed = 0;
INIT_LIST_HEAD(&p->list);
@@ -718,6 +725,10 @@ static void __kprobes __unregister_kprob
struct kprobe *old_p;
if (p->mod_refcounted) {
+ /*
+ * Since we've already incremented refcount,
+ * we don't need to disable preemption.
+ */
mod = module_text_address((unsigned long)p->addr);
if (mod)
module_put(mod);
_
Patches currently in -mm which might be from mhiramat@xxxxxxxxxx are
kprobes-disable-preempt-for-module_text_address-and-kernel_text_address.patch
kprobes-bugfix-try_module_get-even-if-calling_mod-is-null.patch
kprobes-indirectly-call-kprobe_target.patch
kprobes-add-tests-for-register_kprobes.patch
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