On Thu, Nov 01, 2012 at 12:46:37PM -0700, Kees Cook wrote:
> #ifdef CONFIG_SECCOMP
> - tst r10, #_TIF_SECCOMP
> - beq 1f
> - mov r0, scno
> - bl __secure_computing
> - add r0, sp, #S_R0 + S_OFF @ pointer to regs
> - ldmia r0, {r0 - r3} @ have to reload r0 - r3
> -1:
> + tst r10, #_TIF_SECCOMP @ is seccomp enabled?
> + bne __sys_trace
> #endif
>
> tst r10, #_TIF_SYSCALL_WORK @ are we tracing syscalls?
It's pointless having:
tst r10, #_TIF_SECCOMP
bne __sys_trace
tst r10, #_TIF_SYSCALL_WORK
bne __sys_trace
Instead, make TIF_SECCOMP be bit 11, combine it into _TIF_SYSCALL_WORK, and
eliminate all of that CONFIG_SECCOMP block.
> diff --git a/arch/arm/kernel/ptrace.c b/arch/arm/kernel/ptrace.c
> index 739db3a..6b0e14b 100644
> --- a/arch/arm/kernel/ptrace.c
> +++ b/arch/arm/kernel/ptrace.c
> @@ -916,13 +916,15 @@ enum ptrace_syscall_dir {
> PTRACE_SYSCALL_EXIT,
> };
>
> -static int ptrace_syscall_trace(struct pt_regs *regs, int scno,
> - enum ptrace_syscall_dir dir)
> +asmlinkage int syscall_trace_enter(struct pt_regs *regs, int scno)
> {
> unsigned long ip;
>
> current_thread_info()->syscall = scno;
>
> + if (secure_computing(scno) == -1)
> + return -1;
> +
> if (!test_thread_flag(TIF_SYSCALL_TRACE))
> return scno;
I'm not sure this change is correct (combined with your hunk below).
What if we have auditing enabled but trace disabled? How do we reach
audit_syscall_entry()? Or the tracehook stuff?
This patch looks wrong in too many ways.
> @@ -931,20 +933,13 @@ static int ptrace_syscall_trace(struct pt_regs *regs,
> int scno,
> * IP = 0 -> entry, =1 -> exit
> */
> ip = regs->ARM_ip;
> - regs->ARM_ip = dir;
> -
> - if (dir == PTRACE_SYSCALL_EXIT)
> - tracehook_report_syscall_exit(regs, 0);
> - else if (tracehook_report_syscall_entry(regs))
> + regs->ARM_ip = PTRACE_SYSCALL_ENTER;
> + if (tracehook_report_syscall_entry(regs))
> current_thread_info()->syscall = -1;
> -
> regs->ARM_ip = ip;
> - return current_thread_info()->syscall;
> -}
>
> -asmlinkage int syscall_trace_enter(struct pt_regs *regs, int scno)
> -{
> - scno = ptrace_syscall_trace(regs, scno, PTRACE_SYSCALL_ENTER);
> + scno = current_thread_info()->syscall;
> +
> if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))
> trace_sys_enter(regs, scno);
> audit_syscall_entry(AUDIT_ARCH_ARM, scno, regs->ARM_r0, regs->ARM_r1,
> @@ -954,7 +949,23 @@ asmlinkage int syscall_trace_enter(struct pt_regs *regs,
> int scno)
>
> asmlinkage int syscall_trace_exit(struct pt_regs *regs, int scno)
> {
> - scno = ptrace_syscall_trace(regs, scno, PTRACE_SYSCALL_EXIT);
> + unsigned long ip;
> +
> + current_thread_info()->syscall = scno;
> +
> + if (!test_thread_flag(TIF_SYSCALL_TRACE))
> + return scno;
> +
> + /*
> + * IP is used to denote syscall entry/exit:
> + * IP = 0 -> entry, =1 -> exit
> + */
> + ip = regs->ARM_ip;
> + regs->ARM_ip = PTRACE_SYSCALL_EXIT;
> + tracehook_report_syscall_exit(regs, 0);
> + regs->ARM_ip = ip;
> +
> + scno = current_thread_info()->syscall;
> if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))
> trace_sys_exit(regs, scno);
> audit_syscall_exit(regs);
> --
> 1.7.9.5
>
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