Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932443AbaDBPqU (ORCPT ); Wed, 2 Apr 2014 11:46:20 -0400 Received: from mail-we0-f171.google.com ([74.125.82.171]:40490 "EHLO mail-we0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758882AbaDBPoZ (ORCPT ); Wed, 2 Apr 2014 11:44:25 -0400 From: Daniel Thompson To: kgdb-bugreport@lists.sourceforge.net, Jason Wessel Cc: patches@linaro.org, linaro-kernel@lists.linaro.org, Anton Vorontsov , linux-kernel@vger.kernel.org, Greg Kroah-Hartman , Jiri Slaby , Steven Rostedt , Frederic Weisbecker , Ingo Molnar , John Stultz , Colin Cross , kernel-team@android.com, Daniel Thompson Subject: [RFC v2 07/10] kdb: Mark safe commands as KDB_SAFE and KDB_SAFE_NO_ARGS Date: Wed, 2 Apr 2014 16:43:57 +0100 Message-Id: <1396453440-16445-8-git-send-email-daniel.thompson@linaro.org> X-Mailer: git-send-email 1.9.0 In-Reply-To: <1396453440-16445-1-git-send-email-daniel.thompson@linaro.org> References: <1396453440-16445-1-git-send-email-daniel.thompson@linaro.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Anton Vorontsov This patch introduces two new flags: KDB_SAFE, denotes a safe command, and KDB_SAFE_NO_ARGS, denotes a safe command when used without arguments. The word "safe" here used in the sense that the commands cannot be used to leak sensitive data from the memory, and cannot be used to change program flow in a predefined manner. These flags will be used by the "kiosk" mode, i.e. when it is possible for the ordinary user to enter the KDB (or user can get the access to KDB after the crash), but we do not allow user to read dump the memory [and thus read some sensitive data]. The following commands were marked as "safe": Display stack for process Display stack all processes Backtrace current process on each cpu Execute cmd for each element in linked list Show environment variables Set environment variables Display Help Message Switch to new cpu Display active task list Switch to another task Reboot the machine immediately List loaded kernel modules Magic SysRq key Display syslog buffer Define a set of commands, down to endefcmd Summarize the system Disable NMI entry to KDB Macro commands (subject to finer grain checking) The following commands were marked as safe when issued with no arguments: Stack traceback Continue Execution And the following commands are unsafe: Display exception frame Clear Breakpoint Enable Breakpoint Disable Breakpoint Single step Single step to branch/call Continue Execution (with address argument) Display Memory Contents Display Raw Memory Display Physical Memory Display Memory Symbolically Modify Memory Contents Display Registers Modify Registers Backtrace process given its struct task address Send a signal to a process Enter kgdb mode Display per_cpu variables Note that we mark "display registers" command unsafe, this is because single stepping + constantly dumping registers in string or memory functions can be used as a way to read sensitive data (it's actually trivial to exploit). Later we can do a bit better, i.e. not displaying general-purpose registers, but printing control registers. Signed-off-by: Anton Vorontsov Signed-off-by: John Stultz Signed-off-by: Daniel Thompson --- include/linux/kdb.h | 2 ++ kernel/debug/kdb/kdb_main.c | 48 ++++++++++++++++++++++++--------------------- kernel/trace/trace_kdb.c | 2 +- 3 files changed, 29 insertions(+), 23 deletions(-) diff --git a/include/linux/kdb.h b/include/linux/kdb.h index 4b656d6..784b22f 100644 --- a/include/linux/kdb.h +++ b/include/linux/kdb.h @@ -16,6 +16,8 @@ typedef enum { KDB_REPEAT_NO_ARGS = 0x1, /* Repeat the command w/o arguments */ KDB_REPEAT_WITH_ARGS = 0x2, /* Repeat the command w/ its arguments */ + KDB_SAFE = 0x4, /* Security-wise safe command */ + KDB_SAFE_NO_ARGS = 0x8, /* Only safe if run w/o arguments */ } kdb_cmdflags_t; typedef int (*kdb_func_t)(int, const char **); diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index a40b05b..0205e4a 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -641,8 +641,12 @@ static int kdb_defcmd2(const char *cmdstr, const char *argv0) if (!s->count) s->usable = 0; if (s->usable) - kdb_register(s->name, kdb_exec_defcmd, - s->usage, s->help, 0); + /* macros are safe because when executed each + * internal command re-enters kdb_parse() and is + * safety checked individually. + */ + kdb_register_flags(s->name, kdb_exec_defcmd, + s->usage, s->help, 0, KDB_SAFE); return 0; } if (!s->usable) @@ -2767,7 +2771,7 @@ static void __init kdb_inittab(void) kdb_register_flags("mm", kdb_mm, " ", "Modify Memory Contents", 0, KDB_REPEAT_NO_ARGS); kdb_register_flags("go", kdb_go, "[]", - "Continue Execution", 1, 0); + "Continue Execution", 1, KDB_SAFE_NO_ARGS); kdb_register_flags("rd", kdb_rd, "", "Display Registers", 0, 0); kdb_register_flags("rm", kdb_rm, " ", @@ -2775,60 +2779,60 @@ static void __init kdb_inittab(void) kdb_register_flags("ef", kdb_ef, "", "Display exception frame", 0, 0); kdb_register_flags("bt", kdb_bt, "[]", - "Stack traceback", 1, 0); + "Stack traceback", 1, KDB_SAFE_NO_ARGS); kdb_register_flags("btp", kdb_bt, "", - "Display stack for process ", 0, 0); + "Display stack for process ", 0, KDB_SAFE); kdb_register_flags("bta", kdb_bt, "[D|R|S|T|C|Z|E|U|I|M|A]", - "Backtrace all processes matching state flag", 0, 0); + "Backtrace all processes matching state flag", 0, KDB_SAFE); kdb_register_flags("btc", kdb_bt, "", - "Backtrace current process on each cpu", 0, 0); + "Backtrace current process on each cpu", 0, KDB_SAFE); kdb_register_flags("btt", kdb_bt, "", "Backtrace process given its struct task address", 0, 0); kdb_register_flags("env", kdb_env, "", - "Show environment variables", 0, 0); + "Show environment variables", 0, KDB_SAFE); kdb_register_flags("set", kdb_set, "", - "Set environment variables", 0, 0); + "Set environment variables", 0, KDB_SAFE); kdb_register_flags("help", kdb_help, "", - "Display Help Message", 1, 0); + "Display Help Message", 1, KDB_SAFE); kdb_register_flags("?", kdb_help, "", - "Display Help Message", 0, 0); + "Display Help Message", 0, KDB_SAFE); kdb_register_flags("cpu", kdb_cpu, "", - "Switch to new cpu", 0, 0); + "Switch to new cpu", 0, KDB_SAFE); kdb_register_flags("kgdb", kdb_kgdb, "", "Enter kgdb mode", 0, 0); kdb_register_flags("ps", kdb_ps, "[|A]", - "Display active task list", 0, 0); + "Display active task list", 0, KDB_SAFE); kdb_register_flags("pid", kdb_pid, "", - "Switch to another task", 0, 0); + "Switch to another task", 0, KDB_SAFE); kdb_register_flags("reboot", kdb_reboot, "", - "Reboot the machine immediately", 0, 0); + "Reboot the machine immediately", 0, KDB_SAFE); #if defined(CONFIG_MODULES) kdb_register_flags("lsmod", kdb_lsmod, "", - "List loaded kernel modules", 0, 0); + "List loaded kernel modules", 0, KDB_SAFE); #endif #if defined(CONFIG_MAGIC_SYSRQ) kdb_register_flags("sr", kdb_sr, "", - "Magic SysRq key", 0, 0); + "Magic SysRq key", 0, KDB_SAFE); #endif #if defined(CONFIG_PRINTK) kdb_register_flags("dmesg", kdb_dmesg, "[lines]", - "Display syslog buffer", 0, 0); + "Display syslog buffer", 0, KDB_SAFE); #endif if (arch_kgdb_ops.enable_nmi) { kdb_register_flags("disable_nmi", kdb_disable_nmi, "", - "Disable NMI entry to KDB", 0, 0); + "Disable NMI entry to KDB", 0, KDB_SAFE); } kdb_register_flags("defcmd", kdb_defcmd, "name \"usage\" \"help\"", - "Define a set of commands, down to endefcmd", 0, 0); + "Define a set of commands, down to endefcmd", 0, KDB_SAFE); kdb_register_flags("kill", kdb_kill, "<-signal> ", "Send a signal to a process", 0, 0); kdb_register_flags("summary", kdb_summary, "", - "Summarize the system", 4, 0); + "Summarize the system", 4, KDB_SAFE); kdb_register_flags("per_cpu", kdb_per_cpu, " [] []", "Display per_cpu variables", 3, 0); kdb_register_flags("grephelp", kdb_grep_help, "", - "Display help on | grep", 0, 0); + "Display help on | grep", 0, KDB_SAFE); } /* Execute any commands defined in kdb_cmds. */ diff --git a/kernel/trace/trace_kdb.c b/kernel/trace/trace_kdb.c index 3da7e30..52f9ad6 100644 --- a/kernel/trace/trace_kdb.c +++ b/kernel/trace/trace_kdb.c @@ -128,7 +128,7 @@ static int kdb_ftdump(int argc, const char **argv) static __init int kdb_ftrace_register(void) { kdb_register_flags("ftdump", kdb_ftdump, "[skip_#lines] [cpu]", - "Dump ftrace log", 0, 0); + "Dump ftrace log", 0, KDB_SAFE); return 0; } -- 1.9.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/