From 3d7e33825d8799115dd2495c9944badd3272a623 Mon Sep 17 00:00:00 2001 From: Michael Ellerman 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 Cc: Prasanna S Panchamukhi Acked-by: Ananth N Mavinakayanahalli Cc: Anil S Keshavamurthy Cc: David S. Miller Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- 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 5bc46f151344..5dc98b5abcfb 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 0c96611f02f4..440f5a87271f 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 bd892850c94a..51464d12a4e5 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 9e47d8c493f3..3e9f513a728d 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;