Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030341Ab2B2XzL (ORCPT ); Wed, 29 Feb 2012 18:55:11 -0500 Received: from mail-gy0-f174.google.com ([209.85.160.174]:34220 "EHLO mail-gy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030235Ab2B2Xy4 (ORCPT ); Wed, 29 Feb 2012 18:54:56 -0500 Authentication-Results: mr.google.com; spf=pass (google.com: domain of wad@chromium.org designates 10.236.153.6 as permitted sender) smtp.mail=wad@chromium.org; dkim=pass header.i=wad@chromium.org MIME-Version: 1.0 From: Will Drewry To: linux-kernel@vger.kernel.org Cc: linux-arch@vger.kernel.org, linux-doc@vger.kernel.org, kernel-hardening@lists.openwall.com, netdev@vger.kernel.org, x86@kernel.org, arnd@arndb.de, davem@davemloft.net, hpa@zytor.com, mingo@redhat.com, oleg@redhat.com, peterz@infradead.org, rdunlap@xenotime.net, mcgrathr@chromium.org, tglx@linutronix.de, luto@mit.edu, eparis@redhat.com, serge.hallyn@canonical.com, djm@mindrot.org, scarybeasts@gmail.com, indan@nul.nu, pmoore@redhat.com, akpm@linux-foundation.org, corbet@lwn.net, eric.dumazet@gmail.com, markus@chromium.org, coreyb@linux.vnet.ibm.com, keescook@chromium.org, Will Drewry Subject: [PATCH v12 10/13] ptrace,seccomp: Add PTRACE_SECCOMP support Date: Wed, 29 Feb 2012 17:53:37 -0600 Message-Id: <1330559620-23543-10-git-send-email-wad@chromium.org> X-Mailer: git-send-email 1.7.5.4 In-Reply-To: <1330559620-23543-1-git-send-email-wad@chromium.org> References: <1330559620-23543-1-git-send-email-wad@chromium.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5936 Lines: 163 This change adds support for a new ptrace option, PTRACE_O_TRACESECCOMP, and a new return value for seccomp BPF programs, SECCOMP_RET_TRACE. When a tracer specifies the PTRACE_O_TRACESECCOMP ptrace option, the tracer will be notified for any syscall that results in a BPF program returning SECCOMP_RET_TRACE. The 16-bit SECCOMP_RET_DATA mask of the BPF program return value will be passed as the ptrace_message and may be retrieved using PTRACE_GETEVENTMSG. If the subordinate process is not using seccomp filter, then no system call notifications will occur even if the option is specified. If there is no attached tracer when SECCOMP_RET_TRACE is returned, the system call will not be executed and an -ENOSYS errno will be returned to userspace. This change adds a dependency on the system call slow path. Any future efforts to use the system call fast path for seccomp filter will need to address this restriction. v12: - rebase to linux-next - use ptrace_event and update arch/Kconfig to mention slow-path dependency - drop all tracehook changes and inclusion (oleg@redhat.com) v11: - invert the logic to just make it a PTRACE_SYSCALL accelerator (indan@nul.nu) v10: - moved to PTRACE_O_SECCOMP / PT_TRACE_SECCOMP v9: - n/a v8: - guarded PTRACE_SECCOMP use with an ifdef v7: - introduced Signed-off-by: Will Drewry --- arch/Kconfig | 11 ++++++----- include/linux/ptrace.h | 5 ++++- include/linux/seccomp.h | 1 + kernel/seccomp.c | 20 +++++++++++++++----- 4 files changed, 26 insertions(+), 11 deletions(-) diff --git a/arch/Kconfig b/arch/Kconfig index 6908bf6..beb1507 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -236,15 +236,16 @@ config ARCH_WANT_OLD_COMPAT_IPC config HAVE_ARCH_SECCOMP_FILTER bool help - This symbol should be selected by an architecure if it provides: - asm/syscall.h: + An arch should select this symbol if it provides all of these things: - syscall_get_arch() - syscall_get_arguments() - syscall_rollback() - syscall_set_return_value() - SIGSYS siginfo_t support must be implemented. - __secure_computing_int()/secure_computing()'s return value must be - checked, with -1 resulting in the syscall being skipped. + - SIGSYS siginfo_t support + - uses __secure_computing_int() or secure_computing() + - secure_computing is called from a ptrace_event()-safe context + - secure_computing return value is checked and a return value of -1 + results in the system call being skipped immediately. config SECCOMP_FILTER def_bool y diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h index 5c71962..597e4fd 100644 --- a/include/linux/ptrace.h +++ b/include/linux/ptrace.h @@ -58,6 +58,7 @@ #define PTRACE_EVENT_EXEC 4 #define PTRACE_EVENT_VFORK_DONE 5 #define PTRACE_EVENT_EXIT 6 +#define PTRACE_EVENT_SECCOMP 7 /* Extended result codes which enabled by means other than options. */ #define PTRACE_EVENT_STOP 128 @@ -69,8 +70,9 @@ #define PTRACE_O_TRACEEXEC (1 << PTRACE_EVENT_EXEC) #define PTRACE_O_TRACEVFORKDONE (1 << PTRACE_EVENT_VFORK_DONE) #define PTRACE_O_TRACEEXIT (1 << PTRACE_EVENT_EXIT) +#define PTRACE_O_TRACESECCOMP (1 << PTRACE_EVENT_SECCOMP) -#define PTRACE_O_MASK 0x0000007f +#define PTRACE_O_MASK 0x000000ff #include @@ -98,6 +100,7 @@ #define PT_TRACE_EXEC PT_EVENT_FLAG(PTRACE_EVENT_EXEC) #define PT_TRACE_VFORK_DONE PT_EVENT_FLAG(PTRACE_EVENT_VFORK_DONE) #define PT_TRACE_EXIT PT_EVENT_FLAG(PTRACE_EVENT_EXIT) +#define PT_TRACE_SECCOMP PT_EVENT_FLAG(PTRACE_EVENT_SECCOMP) /* single stepping state bits (used on ARM and PA-RISC) */ #define PT_SINGLESTEP_BIT 31 diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h index 3fe48fd..e183598 100644 --- a/include/linux/seccomp.h +++ b/include/linux/seccomp.h @@ -21,6 +21,7 @@ #define SECCOMP_RET_KILL 0x00000000U /* kill the task immediately */ #define SECCOMP_RET_TRAP 0x00020000U /* disallow and force a SIGSYS */ #define SECCOMP_RET_ERRNO 0x00030000U /* returns an errno */ +#define SECCOMP_RET_TRACE 0x7ffe0000U /* pass to a tracer or disallow */ #define SECCOMP_RET_ALLOW 0x7fff0000U /* allow */ /* Masks for the return value sections. */ diff --git a/kernel/seccomp.c b/kernel/seccomp.c index 10c6077..1064327 100644 --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -17,13 +17,13 @@ #include #include #include +#include #include #include #include #include #include -#include #include /* #define SECCOMP_DEBUG 1 */ @@ -346,14 +346,24 @@ int __secure_computing_int(int this_syscall) -(action & SECCOMP_RET_DATA), 0); return -1; - case SECCOMP_RET_TRAP: { - int reason_code = action & SECCOMP_RET_DATA; + case SECCOMP_RET_TRAP: /* Show the handler the original registers. */ syscall_rollback(current, task_pt_regs(current)); /* Let the filter pass back 16 bits of data. */ - seccomp_send_sigsys(this_syscall, reason_code); + seccomp_send_sigsys(this_syscall, + action & SECCOMP_RET_DATA); return -1; - } + case SECCOMP_RET_TRACE: + /* Skip these calls if there is no tracer. */ + if (!ptrace_event_enabled(current, + PTRACE_EVENT_SECCOMP)) + return -1; + /* Allow the BPF to provide the event message */ + ptrace_event(PTRACE_EVENT_SECCOMP, + action & SECCOMP_RET_DATA); + if (fatal_signal_pending(current)) + break; + return 0; case SECCOMP_RET_ALLOW: return 0; case SECCOMP_RET_KILL: -- 1.7.5.4 -- 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/