From 3b84efc066f8793a6581018d92da9b304abd8ce8 Mon Sep 17 00:00:00 2001 From: "Masami Hiramatsu (Google)" Date: Fri, 2 Dec 2022 11:18:52 +0900 Subject: [PATCH] arm64: kprobes: Return DBG_HOOK_ERROR if kprobes can not handle a BRK Return DBG_HOOK_ERROR if kprobes can not handle a BRK because it fails to find a kprobe corresponding to the address. Since arm64 kprobes uses stop_machine based text patching for removing BRK, it ensures all running kprobe_break_handler() is done at that point. And after removing the BRK, it removes the kprobe from its hash list. Thus, if the kprobe_break_handler() fails to find kprobe from hash list, there is a bug. Signed-off-by: Masami Hiramatsu (Google) Acked-by: Mark Rutland Link: https://lore.kernel.org/r/166994753273.439920.6629626290560350760.stgit@devnote3 Signed-off-by: Will Deacon --- arch/arm64/kernel/probes/kprobes.c | 78 ++++++++++++++++++-------------------- 1 file changed, 36 insertions(+), 42 deletions(-) diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c index d2ae37f8..f35d059 100644 --- a/arch/arm64/kernel/probes/kprobes.c +++ b/arch/arm64/kernel/probes/kprobes.c @@ -298,7 +298,8 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr) return 0; } -static void __kprobes kprobe_handler(struct pt_regs *regs) +static int __kprobes +kprobe_breakpoint_handler(struct pt_regs *regs, unsigned long esr) { struct kprobe *p, *cur_kprobe; struct kprobe_ctlblk *kcb; @@ -308,39 +309,44 @@ static void __kprobes kprobe_handler(struct pt_regs *regs) cur_kprobe = kprobe_running(); p = get_kprobe((kprobe_opcode_t *) addr); + if (WARN_ON_ONCE(!p)) { + /* + * Something went wrong. This BRK used an immediate reserved + * for kprobes, but we couldn't find any corresponding probe. + */ + return DBG_HOOK_ERROR; + } - if (p) { - if (cur_kprobe) { - if (reenter_kprobe(p, regs, kcb)) - return; - } else { - /* Probe hit */ - set_current_kprobe(p); - kcb->kprobe_status = KPROBE_HIT_ACTIVE; - - /* - * If we have no pre-handler or it returned 0, we - * continue with normal processing. If we have a - * pre-handler and it returned non-zero, it will - * modify the execution path and no need to single - * stepping. Let's just reset current kprobe and exit. - */ - if (!p->pre_handler || !p->pre_handler(p, regs)) { - setup_singlestep(p, regs, kcb, 0); - } else - reset_current_kprobe(); - } + if (cur_kprobe) { + /* Hit a kprobe inside another kprobe */ + if (!reenter_kprobe(p, regs, kcb)) + return DBG_HOOK_ERROR; + } else { + /* Probe hit */ + set_current_kprobe(p); + kcb->kprobe_status = KPROBE_HIT_ACTIVE; + + /* + * If we have no pre-handler or it returned 0, we + * continue with normal processing. If we have a + * pre-handler and it returned non-zero, it will + * modify the execution path and not need to single-step + * Let's just reset current kprobe and exit. + */ + if (!p->pre_handler || !p->pre_handler(p, regs)) + setup_singlestep(p, regs, kcb, 0); + else + reset_current_kprobe(); } - /* - * The breakpoint instruction was removed right - * after we hit it. Another cpu has removed - * either a probepoint or a debugger breakpoint - * at this address. In either case, no further - * handling of this interrupt is appropriate. - * Return back to original instruction, and continue. - */ + + return DBG_HOOK_HANDLED; } +static struct break_hook kprobes_break_hook = { + .imm = KPROBES_BRK_IMM, + .fn = kprobe_breakpoint_handler, +}; + static int __kprobes kprobe_breakpoint_ss_handler(struct pt_regs *regs, unsigned long esr) { @@ -365,18 +371,6 @@ static struct break_hook kprobes_break_ss_hook = { .fn = kprobe_breakpoint_ss_handler, }; -static int __kprobes -kprobe_breakpoint_handler(struct pt_regs *regs, unsigned long esr) -{ - kprobe_handler(regs); - return DBG_HOOK_HANDLED; -} - -static struct break_hook kprobes_break_hook = { - .imm = KPROBES_BRK_IMM, - .fn = kprobe_breakpoint_handler, -}; - /* * Provide a blacklist of symbols identifying ranges which cannot be kprobed. * This blacklist is exposed to userspace via debugfs (kprobes/blacklist). -- 2.7.4