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Commit 1addc57e authored by Kees Cook's avatar Kees Cook
Browse files

powerpc/ptrace: run seccomp after ptrace 



Close the hole where ptrace can change a syscall out from under seccomp.

Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: linuxppc-dev@lists.ozlabs.org
parent 0208b944

arch/powerpc/kernel/ptrace.c

+23 −21
Original line number Diff line number Diff line
@@ -1788,7 +1788,7 @@ static int do_seccomp(struct pt_regs *regs) 


	/*

	 * The syscall was allowed by seccomp, restore the register

	 * state to what ptrace and audit expect.

	 * state to what audit expects.

	 * Note that we use orig_gpr3, which means a seccomp tracer can

	 * modify the first syscall parameter (in orig_gpr3) and also

	 * allow the syscall to proceed.
@@ -1822,22 +1822,25 @@ static inline int do_seccomp(struct pt_regs *regs) { return 0; } 
 */

long do_syscall_trace_enter(struct pt_regs *regs)

{

	bool abort = false;



	user_exit();



	if (do_seccomp(regs))

		return -1;



	if (test_thread_flag(TIF_SYSCALL_TRACE)) {

	/*

	 * The tracer may decide to abort the syscall, if so tracehook

	 * will return !0. Note that the tracer may also just change

	 * regs->gpr[0] to an invalid syscall number, that is handled

	 * below on the exit path.

	 */

		abort = tracehook_report_syscall_entry(regs) != 0;

	}

	if (test_thread_flag(TIF_SYSCALL_TRACE) &&

	    tracehook_report_syscall_entry(regs))

		goto skip;



	/* Run seccomp after ptrace; allow it to set gpr[3]. */

	if (do_seccomp(regs))

		return -1;



	/* Avoid trace and audit when syscall is invalid. */

	if (regs->gpr[0] >= NR_syscalls)

		goto skip;



	if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))

		trace_sys_enter(regs, regs->gpr[0]);
@@ -1854,7 +1857,10 @@ long do_syscall_trace_enter(struct pt_regs *regs) 
				    regs->gpr[5] & 0xffffffff,

				    regs->gpr[6] & 0xffffffff);



	if (abort || regs->gpr[0] >= NR_syscalls) {

	/* Return the possibly modified but valid syscall number */

	return regs->gpr[0];



skip:

	/*

	 * If we are aborting explicitly, or if the syscall number is

	 * now invalid, set the return value to -ENOSYS.
@@ -1863,10 +1869,6 @@ long do_syscall_trace_enter(struct pt_regs *regs) 
	return -1;

}



	/* Return the possibly modified but valid syscall number */

	return regs->gpr[0];

}



void do_syscall_trace_leave(struct pt_regs *regs)

{

	int step;