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Message-Id: <1331587715-26069-10-git-send-email-wad@chromium.org> Date: Mon, 12 Mar 2012 16:28:32 -0500 From: Will Drewry <wad@...omium.org> To: linux-kernel@...r.kernel.org Cc: linux-arch@...r.kernel.org, linux-doc@...r.kernel.org, kernel-hardening@...ts.openwall.com, netdev@...r.kernel.org, x86@...nel.org, arnd@...db.de, davem@...emloft.net, hpa@...or.com, mingo@...hat.com, oleg@...hat.com, peterz@...radead.org, rdunlap@...otime.net, mcgrathr@...omium.org, tglx@...utronix.de, luto@....edu, eparis@...hat.com, serge.hallyn@...onical.com, djm@...drot.org, scarybeasts@...il.com, indan@....nu, pmoore@...hat.com, akpm@...ux-foundation.org, corbet@....net, eric.dumazet@...il.com, markus@...omium.org, coreyb@...ux.vnet.ibm.com, keescook@...omium.org, Will Drewry <wad@...omium.org> Subject: [PATCH v14 10/13] ptrace,seccomp: Add PTRACE_SECCOMP support 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. v14: - rebase/nochanges v13: - rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc (Brings back a change to ptrace.c and the masks.) v12: - rebase to linux-next - use ptrace_event and update arch/Kconfig to mention slow-path dependency - drop all tracehook changes and inclusion (oleg@...hat.com) v11: - invert the logic to just make it a PTRACE_SYSCALL accelerator (indan@....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 <wad@...omium.org> --- arch/Kconfig | 11 ++++++----- include/linux/ptrace.h | 7 +++++-- include/linux/seccomp.h | 1 + kernel/ptrace.c | 3 +++ kernel/seccomp.c | 20 +++++++++++++++----- 5 files changed, 30 insertions(+), 12 deletions(-) diff --git a/arch/Kconfig b/arch/Kconfig index d92a78e..3f8132c 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -202,15 +202,16 @@ config HAVE_CMPXCHG_DOUBLE 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 c2f1f6a..84b3418 100644 --- a/include/linux/ptrace.h +++ b/include/linux/ptrace.h @@ -62,8 +62,9 @@ #define PTRACE_O_TRACEEXEC 0x00000010 #define PTRACE_O_TRACEVFORKDONE 0x00000020 #define PTRACE_O_TRACEEXIT 0x00000040 +#define PTRACE_O_TRACESECCOMP 0x00000080 -#define PTRACE_O_MASK 0x0000007f +#define PTRACE_O_MASK 0x000000ff /* Wait extended result codes for the above trace options. */ #define PTRACE_EVENT_FORK 1 @@ -73,6 +74,7 @@ #define PTRACE_EVENT_VFORK_DONE 5 #define PTRACE_EVENT_EXIT 6 #define PTRACE_EVENT_STOP 7 +#define PTRACE_EVENT_SECCOMP 8 #include <asm/ptrace.h> @@ -101,8 +103,9 @@ #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) -#define PT_TRACE_MASK 0x000003f4 +#define PT_TRACE_MASK 0x00000ff4 /* 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 e6d4b56..f4c1774 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/ptrace.c b/kernel/ptrace.c index 00ab2ca..8cf6da1 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -551,6 +551,9 @@ static int ptrace_setoptions(struct task_struct *child, unsigned long data) if (data & PTRACE_O_TRACEEXIT) child->ptrace |= PT_TRACE_EXIT; + if (data & PTRACE_O_TRACESECCOMP) + child->ptrace |= PT_TRACE_SECCOMP; + return (data & ~PTRACE_O_MASK) ? -EINVAL : 0; } diff --git a/kernel/seccomp.c b/kernel/seccomp.c index 140490a..ddacc68 100644 --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -17,13 +17,13 @@ #include <linux/audit.h> #include <linux/compat.h> #include <linux/filter.h> +#include <linux/ptrace.h> #include <linux/sched.h> #include <linux/seccomp.h> #include <linux/security.h> #include <linux/slab.h> #include <linux/uaccess.h> -#include <linux/tracehook.h> #include <asm/syscall.h> /* #define SECCOMP_DEBUG 1 */ @@ -389,14 +389,24 @@ 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
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