Merge branch 'x86-seccomp-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 seccomp changes from Ingo Molnar:
 "This tree includes x86 seccomp filter speedups and related preparatory
  work, which touches core seccomp facilities as well.

  The main idea is to split seccomp into two phases, to be able to enter
  a simple fast path for syscalls with ptrace side effects.

  There's no substantial user-visible (and ABI) effects expected from
  this, except a change in how we emit a better audit record for
  SECCOMP_RET_TRACE events"

* 'x86-seccomp-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86_64, entry: Use split-phase syscall_trace_enter for 64-bit syscalls
  x86_64, entry: Treat regs->ax the same in fastpath and slowpath syscalls
  x86: Split syscall_trace_enter into two phases
  x86, entry: Only call user_exit if TIF_NOHZ
  x86, x32, audit: Fix x32's AUDIT_ARCH wrt audit
  seccomp: Document two-phase seccomp and arch-provided seccomp_data
  seccomp: Allow arch code to provide seccomp_data
  seccomp: Refactor the filter callback and the API
  seccomp,x86,arm,mips,s390: Remove nr parameter from secure_computing

3 files changed, 155 insertions, 63 deletions

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 2fac1343a90b..df088bb03fb3 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -404,8 +404,8 @@ GLOBAL(system_call_after_swapgs)
 	 * and short:
 	 */
 	ENABLE_INTERRUPTS(CLBR_NONE)
-	SAVE_ARGS 8,0
-	movq  %rax,ORIG_RAX-ARGOFFSET(%rsp)
+	SAVE_ARGS 8, 0, rax_enosys=1
+	movq_cfi rax,(ORIG_RAX-ARGOFFSET)
 	movq  %rcx,RIP-ARGOFFSET(%rsp)
 	CFI_REL_OFFSET rip,RIP-ARGOFFSET
 	testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET)
@@ -417,7 +417,7 @@ system_call_fastpath:
 	andl $__SYSCALL_MASK,%eax
 	cmpl $__NR_syscall_max,%eax
 #endif
-	ja badsys
+	ja ret_from_sys_call  /* and return regs->ax */
 	movq %r10,%rcx
 	call *sys_call_table(,%rax,8)  # XXX:	 rip relative
 	movq %rax,RAX-ARGOFFSET(%rsp)
@@ -476,28 +476,8 @@ sysret_signal:
 	FIXUP_TOP_OF_STACK %r11, -ARGOFFSET
 	jmp int_check_syscall_exit_work
 
-badsys:
-	movq $-ENOSYS,RAX-ARGOFFSET(%rsp)
-	jmp ret_from_sys_call
-
 #ifdef CONFIG_AUDITSYSCALL
 	/*
-	 * Fast path for syscall audit without full syscall trace.
-	 * We just call __audit_syscall_entry() directly, and then
-	 * jump back to the normal fast path.
-	 */
-auditsys:
-	movq %r10,%r9			/* 6th arg: 4th syscall arg */
-	movq %rdx,%r8			/* 5th arg: 3rd syscall arg */
-	movq %rsi,%rcx			/* 4th arg: 2nd syscall arg */
-	movq %rdi,%rdx			/* 3rd arg: 1st syscall arg */
-	movq %rax,%rsi			/* 2nd arg: syscall number */
-	movl $AUDIT_ARCH_X86_64,%edi	/* 1st arg: audit arch */
-	call __audit_syscall_entry
-	LOAD_ARGS 0		/* reload call-clobbered registers */
-	jmp system_call_fastpath
-
-	/*
 	 * Return fast path for syscall audit.  Call __audit_syscall_exit()
 	 * directly and then jump back to the fast path with TIF_SYSCALL_AUDIT
 	 * masked off.
@@ -514,18 +494,25 @@ sysret_audit:
 
 	/* Do syscall tracing */
 tracesys:
-#ifdef CONFIG_AUDITSYSCALL
-	testl $(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT),TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET)
-	jz auditsys
-#endif
+	leaq -REST_SKIP(%rsp), %rdi
+	movq $AUDIT_ARCH_X86_64, %rsi
+	call syscall_trace_enter_phase1
+	test %rax, %rax
+	jnz tracesys_phase2		/* if needed, run the slow path */
+	LOAD_ARGS 0			/* else restore clobbered regs */
+	jmp system_call_fastpath	/*      and return to the fast path */
+
+tracesys_phase2:
 	SAVE_REST
-	movq $-ENOSYS,RAX(%rsp) /* ptrace can change this for a bad syscall */
 	FIXUP_TOP_OF_STACK %rdi
-	movq %rsp,%rdi
-	call syscall_trace_enter
+	movq %rsp, %rdi
+	movq $AUDIT_ARCH_X86_64, %rsi
+	movq %rax,%rdx
+	call syscall_trace_enter_phase2
+
 	/*
 	 * Reload arg registers from stack in case ptrace changed them.
-	 * We don't reload %rax because syscall_trace_enter() returned
+	 * We don't reload %rax because syscall_trace_entry_phase2() returned
 	 * the value it wants us to use in the table lookup.
 	 */
 	LOAD_ARGS ARGOFFSET, 1
@@ -536,7 +523,7 @@ tracesys:
 	andl $__SYSCALL_MASK,%eax
 	cmpl $__NR_syscall_max,%eax
 #endif
-	ja   int_ret_from_sys_call	/* RAX(%rsp) set to -ENOSYS above */
+	ja   int_ret_from_sys_call	/* RAX(%rsp) is already set */
 	movq %r10,%rcx	/* fixup for C */
 	call *sys_call_table(,%rax,8)
 	movq %rax,RAX-ARGOFFSET(%rsp)
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 678c0ada3b3c..29576c244699 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -1441,24 +1441,126 @@ void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs,
 	force_sig_info(SIGTRAP, &info, tsk);
 }
 
-
-#ifdef CONFIG_X86_32
-# define IS_IA32	1
-#elif defined CONFIG_IA32_EMULATION
-# define IS_IA32	is_compat_task()
-#else
-# define IS_IA32	0
+static void do_audit_syscall_entry(struct pt_regs *regs, u32 arch)
+{
+#ifdef CONFIG_X86_64
+	if (arch == AUDIT_ARCH_X86_64) {
+		audit_syscall_entry(arch, regs->orig_ax, regs->di,
+				    regs->si, regs->dx, regs->r10);
+	} else
 #endif
+	{
+		audit_syscall_entry(arch, regs->orig_ax, regs->bx,
+				    regs->cx, regs->dx, regs->si);
+	}
+}
 
 /*
- * We must return the syscall number to actually look up in the table.
- * This can be -1L to skip running any syscall at all.
+ * We can return 0 to resume the syscall or anything else to go to phase
+ * 2.  If we resume the syscall, we need to put something appropriate in
+ * regs->orig_ax.
+ *
+ * NB: We don't have full pt_regs here, but regs->orig_ax and regs->ax
+ * are fully functional.
+ *
+ * For phase 2's benefit, our return value is:
+ * 0:			resume the syscall
+ * 1:			go to phase 2; no seccomp phase 2 needed
+ * anything else:	go to phase 2; pass return value to seccomp
  */
-long syscall_trace_enter(struct pt_regs *regs)
+unsigned long syscall_trace_enter_phase1(struct pt_regs *regs, u32 arch)
+{
+	unsigned long ret = 0;
+	u32 work;
+
+	BUG_ON(regs != task_pt_regs(current));
+
+	work = ACCESS_ONCE(current_thread_info()->flags) &
+		_TIF_WORK_SYSCALL_ENTRY;
+
+	/*
+	 * If TIF_NOHZ is set, we are required to call user_exit() before
+	 * doing anything that could touch RCU.
+	 */
+	if (work & _TIF_NOHZ) {
+		user_exit();
+		work &= ~TIF_NOHZ;
+	}
+
+#ifdef CONFIG_SECCOMP
+	/*
+	 * Do seccomp first -- it should minimize exposure of other
+	 * code, and keeping seccomp fast is probably more valuable
+	 * than the rest of this.
+	 */
+	if (work & _TIF_SECCOMP) {
+		struct seccomp_data sd;
+
+		sd.arch = arch;
+		sd.nr = regs->orig_ax;
+		sd.instruction_pointer = regs->ip;
+#ifdef CONFIG_X86_64
+		if (arch == AUDIT_ARCH_X86_64) {
+			sd.args[0] = regs->di;
+			sd.args[1] = regs->si;
+			sd.args[2] = regs->dx;
+			sd.args[3] = regs->r10;
+			sd.args[4] = regs->r8;
+			sd.args[5] = regs->r9;
+		} else
+#endif
+		{
+			sd.args[0] = regs->bx;
+			sd.args[1] = regs->cx;
+			sd.args[2] = regs->dx;
+			sd.args[3] = regs->si;
+			sd.args[4] = regs->di;
+			sd.args[5] = regs->bp;
+		}
+
+		BUILD_BUG_ON(SECCOMP_PHASE1_OK != 0);
+		BUILD_BUG_ON(SECCOMP_PHASE1_SKIP != 1);
+
+		ret = seccomp_phase1(&sd);
+		if (ret == SECCOMP_PHASE1_SKIP) {
+			regs->orig_ax = -1;
+			ret = 0;
+		} else if (ret != SECCOMP_PHASE1_OK) {
+			return ret;  /* Go directly to phase 2 */
+		}
+
+		work &= ~_TIF_SECCOMP;
+	}
+#endif
+
+	/* Do our best to finish without phase 2. */
+	if (work == 0)
+		return ret;  /* seccomp and/or nohz only (ret == 0 here) */
+
+#ifdef CONFIG_AUDITSYSCALL
+	if (work == _TIF_SYSCALL_AUDIT) {
+		/*
+		 * If there is no more work to be done except auditing,
+		 * then audit in phase 1.  Phase 2 always audits, so, if
+		 * we audit here, then we can't go on to phase 2.
+		 */
+		do_audit_syscall_entry(regs, arch);
+		return 0;
+	}
+#endif
+
+	return 1;  /* Something is enabled that we can't handle in phase 1 */
+}
+
+/* Returns the syscall nr to run (which should match regs->orig_ax). */
+long syscall_trace_enter_phase2(struct pt_regs *regs, u32 arch,
+				unsigned long phase1_result)
 {
 	long ret = 0;
+	u32 work = ACCESS_ONCE(current_thread_info()->flags) &
+		_TIF_WORK_SYSCALL_ENTRY;
 
-	user_exit();
+	BUG_ON(regs != task_pt_regs(current));
 
 	/*
 	 * If we stepped into a sysenter/syscall insn, it trapped in
@@ -1467,17 +1569,21 @@ long syscall_trace_enter(struct pt_regs *regs)
 	 * do_debug() and we need to set it again to restore the user
 	 * state.  If we entered on the slow path, TF was already set.
 	 */
-	if (test_thread_flag(TIF_SINGLESTEP))
+	if (work & _TIF_SINGLESTEP)
 		regs->flags |= X86_EFLAGS_TF;
 
-	/* do the secure computing check first */
-	if (secure_computing(regs->orig_ax)) {
+#ifdef CONFIG_SECCOMP
+	/*
+	 * Call seccomp_phase2 before running the other hooks so that
+	 * they can see any changes made by a seccomp tracer.
+	 */
+	if (phase1_result > 1 && seccomp_phase2(phase1_result)) {
 		/* seccomp failures shouldn't expose any additional code. */
-		ret = -1L;
-		goto out;
+		return -1;
 	}
+#endif
 
-	if (unlikely(test_thread_flag(TIF_SYSCALL_EMU)))
+	if (unlikely(work & _TIF_SYSCALL_EMU))
 		ret = -1L;
 
 	if ((ret || test_thread_flag(TIF_SYSCALL_TRACE)) &&
@@ -1487,23 +1593,22 @@ long syscall_trace_enter(struct pt_regs *regs)
 	if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
 		trace_sys_enter(regs, regs->orig_ax);
 
-	if (IS_IA32)
-		audit_syscall_entry(AUDIT_ARCH_I386,
-				    regs->orig_ax,
-				    regs->bx, regs->cx,
-				    regs->dx, regs->si);
-#ifdef CONFIG_X86_64
-	else
-		audit_syscall_entry(AUDIT_ARCH_X86_64,
-				    regs->orig_ax,
-				    regs->di, regs->si,
-				    regs->dx, regs->r10);
-#endif
+	do_audit_syscall_entry(regs, arch);
 
-out:
 	return ret ?: regs->orig_ax;
 }
 
+long syscall_trace_enter(struct pt_regs *regs)
+{
+	u32 arch = is_ia32_task() ? AUDIT_ARCH_I386 : AUDIT_ARCH_X86_64;
+	unsigned long phase1_result = syscall_trace_enter_phase1(regs, arch);
+
+	if (phase1_result == 0)
+		return regs->orig_ax;
+	else
+		return syscall_trace_enter_phase2(regs, arch, phase1_result);
+}
+
 void syscall_trace_leave(struct pt_regs *regs)
 {
 	bool step;
diff --git a/arch/x86/kernel/vsyscall_64.c b/arch/x86/kernel/vsyscall_64.c
index e1e1e80fc6a6..957779f4eb40 100644
--- a/arch/x86/kernel/vsyscall_64.c
+++ b/arch/x86/kernel/vsyscall_64.c
@@ -216,7 +216,7 @@ bool emulate_vsyscall(struct pt_regs *regs, unsigned long address)
 	 */
 	regs->orig_ax = syscall_nr;
 	regs->ax = -ENOSYS;
-	tmp = secure_computing(syscall_nr);
+	tmp = secure_computing();
 	if ((!tmp && regs->orig_ax != syscall_nr) || regs->ip != address) {
 		warn_bad_vsyscall(KERN_DEBUG, regs,
 				  "seccomp tried to change syscall nr or ip");