Commit-ID: 6381c24cd6d5d6373620426ab0a96c80ed953e20 Gitweb: http://git.kernel.org/tip/6381c24cd6d5d6373620426ab0a96c80ed953e20 Author: Masami Hiramatsu <[email protected]> AuthorDate: Thu, 17 Apr 2014 17:16:44 +0900 Committer: Ingo Molnar <[email protected]> CommitDate: Thu, 17 Apr 2014 10:57:02 +0200
kprobes/x86: Fix page-fault handling logic Current kprobes in-kernel page fault handler doesn't expect that its single-stepping can be interrupted by an NMI handler which may cause a page fault(e.g. perf with callback tracing). In that case, the page-fault handled by kprobes and it misunderstands the page-fault has been caused by the single-stepping code and tries to recover IP address to probed address. But the truth is the page-fault has been caused by the NMI handler, and do_page_fault failes to handle real page fault because the IP address is modified and causes Kernel BUGs like below. ---- [ 2264.726905] BUG: unable to handle kernel NULL pointer dereference at 0000000000000020 [ 2264.727190] IP: [<ffffffff813c46e0>] copy_user_generic_string+0x0/0x40 To handle this correctly, I fixed the kprobes fault handler to ensure the faulted ip address is its own single-step buffer instead of checking current kprobe state. Signed-off-by: Masami Hiramatsu <[email protected]> Cc: Andi Kleen <[email protected]> Cc: Ananth N Mavinakayanahalli <[email protected]> Cc: Sandeepa Prabhu <[email protected]> Cc: Frederic Weisbecker <[email protected]> Cc: Steven Rostedt <[email protected]> Cc: [email protected] Cc: [email protected] Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> --- arch/x86/kernel/kprobes/core.c | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-) diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c index 79a3f96..61b17dc 100644 --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -897,9 +897,10 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr) struct kprobe *cur = kprobe_running(); struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); - switch (kcb->kprobe_status) { - case KPROBE_HIT_SS: - case KPROBE_REENTER: + if (unlikely(regs->ip == (unsigned long)cur->ainsn.insn)) { + /* This must happen on single-stepping */ + WARN_ON(kcb->kprobe_status != KPROBE_HIT_SS && + kcb->kprobe_status != KPROBE_REENTER); /* * We are here because the instruction being single * stepped caused a page fault. We reset the current @@ -914,9 +915,8 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr) else reset_current_kprobe(); preempt_enable_no_resched(); - break; - case KPROBE_HIT_ACTIVE: - case KPROBE_HIT_SSDONE: + } else if (kcb->kprobe_status == KPROBE_HIT_ACTIVE || + kcb->kprobe_status == KPROBE_HIT_SSDONE) { /* * We increment the nmissed count for accounting, * we can also use npre/npostfault count for accounting @@ -945,10 +945,8 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr) * fixup routine could not handle it, * Let do_page_fault() fix it. */ - break; - default: - break; } + return 0; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
