Close the hole where ptrace can change a syscall out from under seccomp.
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
---
arch/powerpc/kernel/ptrace.c | 44 +++++++++++++++++++++++---------------------
1 file changed, 23 insertions(+), 21 deletions(-)
diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c
index ed799e994773..5dc47ebb3840 100644
--- a/arch/powerpc/kernel/ptrace.c
+++ b/arch/powerpc/kernel/ptrace.c
@@ -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();
+ /*
+ * 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.
+ */
+ 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;
- 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;
- }
+ /* 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]);
@@ -1854,17 +1857,16 @@ long do_syscall_trace_enter(struct pt_regs *regs)
regs->gpr[5] & 0xffffffff,
regs->gpr[6] & 0xffffffff);
- if (abort || regs->gpr[0] >= NR_syscalls) {
- /*
- * If we are aborting explicitly, or if the syscall number is
- * now invalid, set the return value to -ENOSYS.
- */
- regs->gpr[3] = -ENOSYS;
- return -1;
- }
-
/* 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.
+ */
+ regs->gpr[3] = -ENOSYS;
+ return -1;
}
void do_syscall_trace_leave(struct pt_regs *regs)
--
2.7.4
