[PATCH 3/3] Make jprobes a little safer for users
From: Michael Ellerman <hidden>
Date: 2007-06-26 01:49:45
Also in:
linux-arch, lkml
Subsystem:
kprobes, linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Naveen N Rao, "David S. Miller", Masami Hiramatsu, Madhavan Srinivasan, Linus Torvalds
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 <redacted>
---
arch/ia64/kernel/kprobes.c | 7 ++++++-
arch/powerpc/kernel/kprobes.c | 11 ++++++++---
kernel/kprobes.c | 9 +++++++++
3 files changed, 23 insertions(+), 4 deletions(-)
diff --git a/arch/ia64/kernel/kprobes.c b/arch/ia64/kernel/kprobes.c
index 5bc46f1..5dc98b5 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 0c96611..440f5a8 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/kernel/kprobes.c b/kernel/kprobes.c
index 9e47d8c..3e9f513 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;
--
1.5.1.3.g7a33b