From 3d7e33825d8799115dd2495c9944badd3272a623 Mon Sep 17 00:00:00 2001
From: Michael Ellerman <michael@ellerman.id.au>
Date: Thu, 19 Jul 2007 01:48:11 -0700
Subject: [PATCH] jprobes: make jprobes a little safer for users
I realise jprobes are a razor-blades-included type of interface, but that
doesn't mean we can't try and make them safer to use. This guy I know once
wrote code like this:
struct jprobe jp = { .kp.symbol_name = "foo", .entry = "jprobe_foo" };
And then his kernel exploded. Oops.
This patch adds an arch hook, arch_deref_entry_point() (I don't like it
either) which takes the void * in a struct jprobe, and gives back the text
address that it represents.
We can then use that in register_jprobe() to check that the entry point we're
passed is actually in the kernel text, rather than just some random value.
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Cc: Prasanna S Panchamukhi <prasanna@in.ibm.com>
Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
arch/ia64/kernel/kprobes.c | 7 ++++++-
arch/powerpc/kernel/kprobes.c | 11 ++++++++---
include/linux/kprobes.h | 1 +
kernel/kprobes.c | 9 +++++++++
4 files changed, 24 insertions(+), 4 deletions(-)
diff --git a/arch/ia64/kernel/kprobes.c b/arch/ia64/kernel/kprobes.c
index 5bc46f1513443..5dc98b5abcfbc 100644
--- a/arch/ia64/kernel/kprobes.c
+++ b/arch/ia64/kernel/kprobes.c
@@ -936,10 +936,15 @@ static void ia64_get_bsp_cfm(struct unw_frame_info *info, void *arg)
return;
}
+unsigned long arch_deref_entry_point(void *entry)
+{
+ return ((struct fnptr *)entry)->ip;
+}
+
int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
{
struct jprobe *jp = container_of(p, struct jprobe, kp);
- unsigned long addr = ((struct fnptr *)(jp->entry))->ip;
+ unsigned long addr = arch_deref_entry_point(jp->entry);
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
struct param_bsp_cfm pa;
int bytes;
diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index 0c96611f02f48..440f5a87271fa 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -492,6 +492,13 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
return ret;
}
+#ifdef CONFIG_PPC64
+unsigned long arch_deref_entry_point(void *entry)
+{
+ return (unsigned long)(((func_descr_t *)entry)->entry);
+}
+#endif
+
int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
{
struct jprobe *jp = container_of(p, struct jprobe, kp);
@@ -500,11 +507,9 @@ int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
/* setup return addr to the jprobe handler routine */
+ regs->nip = arch_deref_entry_point(jp->entry);
#ifdef CONFIG_PPC64
- regs->nip = (unsigned long)(((func_descr_t *)jp->entry)->entry);
regs->gpr[2] = (unsigned long)(((func_descr_t *)jp->entry)->toc);
-#else
- regs->nip = (unsigned long)jp->entry;
#endif
return 1;
diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index bd892850c94ab..51464d12a4e5a 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -214,6 +214,7 @@ int longjmp_break_handler(struct kprobe *, struct pt_regs *);
int register_jprobe(struct jprobe *p);
void unregister_jprobe(struct jprobe *p);
void jprobe_return(void);
+unsigned long arch_deref_entry_point(void *);
int register_kretprobe(struct kretprobe *rp);
void unregister_kretprobe(struct kretprobe *rp);
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 9e47d8c493f3a..3e9f513a728d4 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -675,9 +675,18 @@ static struct notifier_block kprobe_exceptions_nb = {
.priority = 0x7fffffff /* we need to be notified first */
};
+unsigned long __weak arch_deref_entry_point(void *entry)
+{
+ return (unsigned long)entry;
+}
int __kprobes register_jprobe(struct jprobe *jp)
{
+ unsigned long addr = arch_deref_entry_point(jp->entry);
+
+ if (!kernel_text_address(addr))
+ return -EINVAL;
+
/* Todo: Verify probepoint is a function entry point */
jp->kp.pre_handler = setjmp_pre_handler;
jp->kp.break_handler = longjmp_break_handler;
--
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