From 2a6730c8b6e075adf826a89a3e2caa705807afdb Mon Sep 17 00:00:00 2001 From: Petr Mladek Date: Fri, 20 Feb 2015 15:07:30 +0100 Subject: [PATCH] kprobes/x86: Check for invalid ftrace location in __recover_probed_insn() __recover_probed_insn() should always be called from an address where an instructions starts. The check for ftrace_location() might help to discover a potential inconsistency. This patch adds WARN_ON() when the inconsistency is detected. Also it adds handling of the situation when the original code can not get recovered. Suggested-by: Masami Hiramatsu Signed-off-by: Petr Mladek Cc: Ananth NMavinakayanahalli Cc: Anil S Keshavamurthy Cc: David S. Miller Cc: Frederic Weisbecker Cc: Jiri Kosina Cc: Steven Rostedt Link: http://lkml.kernel.org/r/1424441250-27146-3-git-send-email-pmladek@suse.cz Signed-off-by: Ingo Molnar --- arch/x86/kernel/kprobes/core.c | 12 ++++++++++++ arch/x86/kernel/kprobes/opt.c | 2 ++ 2 files changed, 14 insertions(+) diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c index c3b4b46b4797..4e3d5a9621fe 100644 --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -227,6 +227,13 @@ __recover_probed_insn(kprobe_opcode_t *buf, unsigned long addr) kp = get_kprobe((void *)addr); faddr = ftrace_location(addr); + /* + * Addresses inside the ftrace location are refused by + * arch_check_ftrace_location(). Something went terribly wrong + * if such an address is checked here. + */ + if (WARN_ON(faddr && faddr != addr)) + return 0UL; /* * Use the current code if it is not modified by Kprobe * and it cannot be modified by ftrace. @@ -265,6 +272,7 @@ __recover_probed_insn(kprobe_opcode_t *buf, unsigned long addr) * Recover the probed instruction at addr for further analysis. * Caller must lock kprobes by kprobe_mutex, or disable preemption * for preventing to release referencing kprobes. + * Returns zero if the instruction can not get recovered. */ unsigned long recover_probed_instruction(kprobe_opcode_t *buf, unsigned long addr) { @@ -299,6 +307,8 @@ static int can_probe(unsigned long paddr) * normally used, we just go through if there is no kprobe. */ __addr = recover_probed_instruction(buf, addr); + if (!__addr) + return 0; kernel_insn_init(&insn, (void *)__addr, MAX_INSN_SIZE); insn_get_length(&insn); @@ -347,6 +357,8 @@ int __copy_instruction(u8 *dest, u8 *src) unsigned long recovered_insn = recover_probed_instruction(buf, (unsigned long)src); + if (!recovered_insn) + return 0; kernel_insn_init(&insn, (void *)recovered_insn, MAX_INSN_SIZE); insn_get_length(&insn); /* Another subsystem puts a breakpoint, failed to recover */ diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c index 7c523bbf3dc8..3aef248ec1ee 100644 --- a/arch/x86/kernel/kprobes/opt.c +++ b/arch/x86/kernel/kprobes/opt.c @@ -259,6 +259,8 @@ static int can_optimize(unsigned long paddr) */ return 0; recovered_insn = recover_probed_instruction(buf, addr); + if (!recovered_insn) + return 0; kernel_insn_init(&insn, (void *)recovered_insn, MAX_INSN_SIZE); insn_get_length(&insn); /* Another subsystem puts a breakpoint */ -- 2.20.1