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Commit 93e35efb authored by Kees Cook's avatar Kees Cook
Browse files

x86/ptrace: run seccomp after ptrace 



This moves seccomp after ptrace on x86 to that seccomp can catch changes
made by ptrace. Emulation should skip the rest of processing too.

We can get rid of test_thread_flag because there's no longer any
opportunity for seccomp to mess with ptrace state before invoking
ptrace.

Suggested-by: default avatarAndy Lutomirski <luto@kernel.org>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Cc: x86@kernel.org
Cc: Andy Lutomirski <luto@kernel.org>
parent ce6526e8

arch/x86/entry/common.c

+12 −10
Original line number Diff line number Diff line
@@ -73,6 +73,7 @@ static long syscall_trace_enter(struct pt_regs *regs) 


	struct thread_info *ti = pt_regs_to_thread_info(regs);

	unsigned long ret = 0;

	bool emulated = false;

	u32 work;



	if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
@@ -80,11 +81,19 @@ static long syscall_trace_enter(struct pt_regs *regs) 


	work = ACCESS_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY;



	if (unlikely(work & _TIF_SYSCALL_EMU))

		emulated = true;



	if ((emulated || (work & _TIF_SYSCALL_TRACE)) &&

	    tracehook_report_syscall_entry(regs))

		return -1L;



	if (emulated)

		return -1L;



#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.

	 * Do seccomp after ptrace, to catch any tracer changes.

	 */

	if (work & _TIF_SECCOMP) {

		struct seccomp_data sd;
@@ -117,13 +126,6 @@ static long syscall_trace_enter(struct pt_regs *regs) 
	}

#endif



	if (unlikely(work & _TIF_SYSCALL_EMU))

		ret = -1L;



	if ((ret || test_thread_flag(TIF_SYSCALL_TRACE)) &&

	    tracehook_report_syscall_entry(regs))

		ret = -1L;



	if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))

		trace_sys_enter(regs, regs->orig_ax);