From patchwork Wed Aug 28 03:46:12 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Christopher M. Riedl" X-Patchwork-Id: 11117761 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 39A8714D5 for ; Wed, 28 Aug 2019 03:43:19 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 903D42080F for ; Wed, 28 Aug 2019 03:43:18 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 903D42080F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=informatik.wtf Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-16808-patchwork-kernel-hardening=patchwork.kernel.org@lists.openwall.com Received: (qmail 16047 invoked by uid 550); 28 Aug 2019 03:43:01 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 15800 invoked from network); 28 Aug 2019 03:42:59 -0000 From: "Christopher M. Riedl" To: linuxppc-dev@ozlabs.org, kernel-hardening@lists.openwall.com Cc: ajd@linux.ibm.com Subject: [PATCH v5 1/2] powerpc/xmon: Allow listing and clearing breakpoints in read-only mode Date: Tue, 27 Aug 2019 22:46:12 -0500 Message-Id: <20190828034613.14750-2-cmr@informatik.wtf> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20190828034613.14750-1-cmr@informatik.wtf> References: <20190828034613.14750-1-cmr@informatik.wtf> MIME-Version: 1.0 X-Virus-Scanned: ClamAV using ClamSMTP Read-only mode should not prevent listing and clearing any active breakpoints. Signed-off-by: Christopher M. Riedl Tested-by: Daniel Axtens Reviewed-by: Daniel Axtens --- arch/powerpc/xmon/xmon.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c index d0620d762a5a..a98a354d46ac 100644 --- a/arch/powerpc/xmon/xmon.c +++ b/arch/powerpc/xmon/xmon.c @@ -1045,10 +1045,6 @@ cmds(struct pt_regs *excp) set_lpp_cmd(); break; case 'b': - if (xmon_is_ro) { - printf(xmon_ro_msg); - break; - } bpt_cmds(); break; case 'C': @@ -1317,11 +1313,16 @@ bpt_cmds(void) struct bpt *bp; cmd = inchar(); + switch (cmd) { #ifndef CONFIG_PPC_8xx static const char badaddr[] = "Only kernel addresses are permitted for breakpoints\n"; int mode; case 'd': /* bd - hardware data breakpoint */ + if (xmon_is_ro) { + printf(xmon_ro_msg); + break; + } if (!ppc_breakpoint_available()) { printf("Hardware data breakpoint not supported on this cpu\n"); break; @@ -1349,6 +1350,10 @@ bpt_cmds(void) break; case 'i': /* bi - hardware instr breakpoint */ + if (xmon_is_ro) { + printf(xmon_ro_msg); + break; + } if (!cpu_has_feature(CPU_FTR_ARCH_207S)) { printf("Hardware instruction breakpoint " "not supported on this cpu\n"); @@ -1407,7 +1412,7 @@ bpt_cmds(void) break; } termch = cmd; - if (!scanhex(&a)) { + if (xmon_is_ro || !scanhex(&a)) { /* print all breakpoints */ printf(" type address\n"); if (dabr.enabled) { From patchwork Wed Aug 28 03:46:13 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Christopher M. Riedl" X-Patchwork-Id: 11117759 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 5507414D5 for ; Wed, 28 Aug 2019 03:43:11 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 7AE7220830 for ; Wed, 28 Aug 2019 03:43:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7AE7220830 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=informatik.wtf Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-16807-patchwork-kernel-hardening=patchwork.kernel.org@lists.openwall.com Received: (qmail 15904 invoked by uid 550); 28 Aug 2019 03:43:01 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 15801 invoked from network); 28 Aug 2019 03:42:59 -0000 From: "Christopher M. Riedl" To: linuxppc-dev@ozlabs.org, kernel-hardening@lists.openwall.com Cc: ajd@linux.ibm.com Subject: [PATCH v5 2/2] powerpc/xmon: Restrict when kernel is locked down Date: Tue, 27 Aug 2019 22:46:13 -0500 Message-Id: <20190828034613.14750-3-cmr@informatik.wtf> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20190828034613.14750-1-cmr@informatik.wtf> References: <20190828034613.14750-1-cmr@informatik.wtf> MIME-Version: 1.0 X-Virus-Scanned: ClamAV using ClamSMTP Xmon should be either fully or partially disabled depending on the kernel lockdown state. Put xmon into read-only mode for lockdown=integrity and prevent user entry into xmon when lockdown=confidentiality. Xmon checks the lockdown state on every attempted entry: (1) during early xmon'ing (2) when triggered via sysrq (3) when toggled via debugfs (4) when triggered via a previously enabled breakpoint The following lockdown state transitions are handled: (1) lockdown=none -> lockdown=integrity set xmon read-only mode (2) lockdown=none -> lockdown=confidentiality clear all breakpoints, set xmon read-only mode, prevent user re-entry into xmon (3) lockdown=integrity -> lockdown=confidentiality clear all breakpoints, set xmon read-only mode, prevent user re-entry into xmon Suggested-by: Andrew Donnellan Signed-off-by: Christopher M. Riedl Tested-by: Daniel Axtens Reviewed-by: Daniel Axtens --- arch/powerpc/xmon/xmon.c | 85 ++++++++++++++++++++++++++++-------- include/linux/security.h | 2 + security/lockdown/lockdown.c | 2 + 3 files changed, 72 insertions(+), 17 deletions(-) diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c index a98a354d46ac..94a5fada3034 100644 --- a/arch/powerpc/xmon/xmon.c +++ b/arch/powerpc/xmon/xmon.c @@ -25,6 +25,7 @@ #include #include #include +#include #include #include @@ -187,6 +188,8 @@ static void dump_tlb_44x(void); static void dump_tlb_book3e(void); #endif +static void clear_all_bpt(void); + #ifdef CONFIG_PPC64 #define REG "%.16lx" #else @@ -283,10 +286,38 @@ Commands:\n\ " U show uptime information\n" " ? help\n" " # n limit output to n lines per page (for dp, dpa, dl)\n" -" zr reboot\n\ - zh halt\n" +" zr reboot\n" +" zh halt\n" ; +#ifdef CONFIG_SECURITY +static bool xmon_is_locked_down(void) +{ + static bool lockdown; + + if (!lockdown) { + lockdown = !!security_locked_down(LOCKDOWN_XMON_RW); + if (lockdown) { + printf("xmon: Disabled due to kernel lockdown\n"); + xmon_is_ro = true; + } + } + + if (!xmon_is_ro) { + xmon_is_ro = !!security_locked_down(LOCKDOWN_XMON_WR); + if (xmon_is_ro) + printf("xmon: Read-only due to kernel lockdown\n"); + } + + return lockdown; +} +#else /* CONFIG_SECURITY */ +static inline bool xmon_is_locked_down(void) +{ + return false; +} +#endif + static struct pt_regs *xmon_regs; static inline void sync(void) @@ -438,7 +469,10 @@ static bool wait_for_other_cpus(int ncpus) return false; } -#endif /* CONFIG_SMP */ +#else /* CONFIG_SMP */ +static inline void get_output_lock(void) {} +static inline void release_output_lock(void) {} +#endif static inline int unrecoverable_excp(struct pt_regs *regs) { @@ -455,6 +489,7 @@ static int xmon_core(struct pt_regs *regs, int fromipi) int cmd = 0; struct bpt *bp; long recurse_jmp[JMP_BUF_LEN]; + bool locked_down; unsigned long offset; unsigned long flags; #ifdef CONFIG_SMP @@ -465,6 +500,8 @@ static int xmon_core(struct pt_regs *regs, int fromipi) local_irq_save(flags); hard_irq_disable(); + locked_down = xmon_is_locked_down(); + tracing_enabled = tracing_is_on(); tracing_off(); @@ -516,7 +553,8 @@ static int xmon_core(struct pt_regs *regs, int fromipi) if (!fromipi) { get_output_lock(); - excprint(regs); + if (!locked_down) + excprint(regs); if (bp) { printf("cpu 0x%x stopped at breakpoint 0x%tx (", cpu, BP_NUM(bp)); @@ -568,10 +606,14 @@ static int xmon_core(struct pt_regs *regs, int fromipi) } remove_bpts(); disable_surveillance(); - /* for breakpoint or single step, print the current instr. */ - if (bp || TRAP(regs) == 0xd00) - ppc_inst_dump(regs->nip, 1, 0); - printf("enter ? for help\n"); + + if (!locked_down) { + /* for breakpoint or single step, print curr insn */ + if (bp || TRAP(regs) == 0xd00) + ppc_inst_dump(regs->nip, 1, 0); + printf("enter ? for help\n"); + } + mb(); xmon_gate = 1; barrier(); @@ -595,8 +637,9 @@ static int xmon_core(struct pt_regs *regs, int fromipi) spin_cpu_relax(); touch_nmi_watchdog(); } else { - cmd = cmds(regs); - if (cmd != 0) { + if (!locked_down) + cmd = cmds(regs); + if (locked_down || cmd != 0) { /* exiting xmon */ insert_bpts(); xmon_gate = 0; @@ -633,13 +676,16 @@ static int xmon_core(struct pt_regs *regs, int fromipi) "can't continue\n"); remove_bpts(); disable_surveillance(); - /* for breakpoint or single step, print the current instr. */ - if (bp || TRAP(regs) == 0xd00) - ppc_inst_dump(regs->nip, 1, 0); - printf("enter ? for help\n"); + if (!locked_down) { + /* for breakpoint or single step, print current insn */ + if (bp || TRAP(regs) == 0xd00) + ppc_inst_dump(regs->nip, 1, 0); + printf("enter ? for help\n"); + } } - cmd = cmds(regs); + if (!locked_down) + cmd = cmds(regs); insert_bpts(); in_xmon = 0; @@ -668,7 +714,10 @@ static int xmon_core(struct pt_regs *regs, int fromipi) } } #endif - insert_cpu_bpts(); + if (locked_down) + clear_all_bpt(); + else + insert_cpu_bpts(); touch_nmi_watchdog(); local_irq_restore(flags); @@ -3767,7 +3816,6 @@ static int __init setup_xmon_sysrq(void) device_initcall(setup_xmon_sysrq); #endif /* CONFIG_MAGIC_SYSRQ */ -#ifdef CONFIG_DEBUG_FS static void clear_all_bpt(void) { int i; @@ -3786,9 +3834,12 @@ static void clear_all_bpt(void) dabr.enabled = 0; } + get_output_lock(); printf("xmon: All breakpoints cleared\n"); + release_output_lock(); } +#ifdef CONFIG_DEBUG_FS static int xmon_dbgfs_set(void *data, u64 val) { xmon_on = !!val; diff --git a/include/linux/security.h b/include/linux/security.h index 429f9f03372b..ba9d308689b6 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -116,12 +116,14 @@ enum lockdown_reason { LOCKDOWN_MODULE_PARAMETERS, LOCKDOWN_MMIOTRACE, LOCKDOWN_DEBUGFS, + LOCKDOWN_XMON_WR, LOCKDOWN_INTEGRITY_MAX, LOCKDOWN_KCORE, LOCKDOWN_KPROBES, LOCKDOWN_BPF_READ, LOCKDOWN_PERF, LOCKDOWN_TRACEFS, + LOCKDOWN_XMON_RW, LOCKDOWN_CONFIDENTIALITY_MAX, }; diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c index 0068cec77c05..db85182d3f11 100644 --- a/security/lockdown/lockdown.c +++ b/security/lockdown/lockdown.c @@ -31,12 +31,14 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = { [LOCKDOWN_MODULE_PARAMETERS] = "unsafe module parameters", [LOCKDOWN_MMIOTRACE] = "unsafe mmio", [LOCKDOWN_DEBUGFS] = "debugfs access", + [LOCKDOWN_XMON_WR] = "xmon write access", [LOCKDOWN_INTEGRITY_MAX] = "integrity", [LOCKDOWN_KCORE] = "/proc/kcore access", [LOCKDOWN_KPROBES] = "use of kprobes", [LOCKDOWN_BPF_READ] = "use of bpf to read kernel RAM", [LOCKDOWN_PERF] = "unsafe use of perf", [LOCKDOWN_TRACEFS] = "use of tracefs", + [LOCKDOWN_XMON_RW] = "xmon read and write access", [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality", };