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SubjectRe: [PATCH v11 10/12] ptrace,seccomp: Add PTRACE_SECCOMP support
On 02/24, Will Drewry wrote:
>
> arch/Kconfig | 1 +
> include/linux/ptrace.h | 7 +++++--
> include/linux/seccomp.h | 4 +++-
> include/linux/tracehook.h | 6 ++++++
> kernel/ptrace.c | 4 ++++
> kernel/seccomp.c | 18 ++++++++++++++++++

FYI, this conflicts with the changes -mm tree.

The changes in ptrace.* confict with Denys's
"ptrace: simplify PTRACE_foo constants and PTRACE_SETOPTIONS code"

The change in tracehook.h conflicts with
"ptrace: the killed tracee should not enter the syscall"

> --- a/kernel/seccomp.c
> +++ b/kernel/seccomp.c
> @@ -354,6 +354,24 @@ int __secure_computing_int(int this_syscall)
> seccomp_send_sigsys(this_syscall, reason_code);
> return -1;
> }
> + case SECCOMP_RET_TRACE: {
> + int ret;
> + struct pt_regs *regs = task_pt_regs(current);
> + if (!(test_tsk_thread_flag(current, TIF_SYSCALL_TRACE)) ||
> + !(current->ptrace & PT_TRACE_SECCOMP))
> + return -1;
> + /*
> + * PT_TRACE_SECCOMP and seccomp.trace indicate whether
> + * tracehook_report_syscall_entry needs to signal the
> + * tracer. This avoids race conditions in hand off and
> + * the requirement for TIF_SYSCALL_TRACE ensures that
> + * we are in the syscall slow path.
> + */
> + current->seccomp.trace = 1;
> + ret = tracehook_report_syscall_entry(regs);
> + current->seccomp.trace = 0;
> + return ret;

To be honest, this interface looks a bit strange to me...

Once again, sorry if this was already discussed. But perhaps it would
be better to introduce PTRACE_EVENT_SECCOMP/PTRACE_O_SECCOMP instead?

SECCOMP_RET_TRACE: could simply do ptrace_event(PTRACE_EVENT_SECCOMP)
unconditionaly. The tracer can set the option and do PTRACE_CONT if it
doesn't want the system call notifications.

This is also much simpler, no need to change ptrace/tracehook files.

Oleg.



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