Messages in this thread Patch in this message | | | Date | Wed, 05 Feb 2014 10:54:27 +0900 | From | AKASHI Takahiro <> | Subject | Re: [PATCH v3 3/3] arm64: audit: Add audit hook in ptrace/syscall_trace |
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On 02/05/2014 02:31 AM, Will Deacon wrote: > On Mon, Feb 03, 2014 at 06:56:30AM +0000, AKASHI Takahiro wrote: >> This patch adds auditing functions on entry to or exit from >> every system call invocation. >> >> Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org> >> --- >> arch/arm64/include/asm/thread_info.h | 1 + >> arch/arm64/kernel/entry.S | 3 +++ >> arch/arm64/kernel/ptrace.c | 10 ++++++++++ >> 3 files changed, 14 insertions(+) >> >> diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h >> index 720e70b..7468388 100644 >> --- a/arch/arm64/include/asm/thread_info.h >> +++ b/arch/arm64/include/asm/thread_info.h >> @@ -101,6 +101,7 @@ static inline struct thread_info *current_thread_info(void) >> #define TIF_NEED_RESCHED 1 >> #define TIF_NOTIFY_RESUME 2 /* callback before returning to user */ >> #define TIF_SYSCALL_TRACE 8 >> +#define TIF_SYSCALL_AUDIT 9 >> #define TIF_POLLING_NRFLAG 16 >> #define TIF_MEMDIE 18 /* is terminating due to OOM killer */ >> #define TIF_FREEZE 19 >> diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S >> index 827cbad..83c4b29 100644 >> --- a/arch/arm64/kernel/entry.S >> +++ b/arch/arm64/kernel/entry.S >> @@ -630,6 +630,9 @@ el0_svc_naked: // compat entry point >> get_thread_info tsk >> ldr x16, [tsk, #TI_FLAGS] // check for syscall tracing >> tbnz x16, #TIF_SYSCALL_TRACE, __sys_trace // are we tracing syscalls? >> +#ifdef CONFIG_AUDITSYSCALL >> + tbnz x16, #TIF_SYSCALL_AUDIT, __sys_trace // auditing syscalls? >> +#endif > > Could we avoid the back-to-back tbnz instructions with a single mask? It's > not obvious that it will end up any better, but it would be good to know.
When first implementing ftrace support, TIF_SYSCALL_TRACEPOINT is defined as 10 and 'tst' instruction doesn't allow the following code: tst x16, #(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_TRACEPOINT)
That is why I've used "back-to-back" tbnz since then, but now that I'm going to submit ftrace, audit and later seccomp, I will replace it with: #define TIF_SYSCALL_WORK (_TIF_SYSCALL_TRACE|TRACEPOINT|AUDIT|SECCOMP)
tst x16, #TIF_SYSCALL_WORK b.ne __syscall_trace
>> adr lr, ret_fast_syscall // return address >> cmp scno, sc_nr // check upper syscall limit >> b.hs ni_sys >> diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c >> index 6777a21..75a3f23 100644 >> --- a/arch/arm64/kernel/ptrace.c >> +++ b/arch/arm64/kernel/ptrace.c >> @@ -19,6 +19,7 @@ >> * along with this program. If not, see <http://www.gnu.org/licenses/>. >> */ >> >> +#include <linux/audit.h> >> #include <linux/kernel.h> >> #include <linux/sched.h> >> #include <linux/mm.h> >> @@ -38,6 +39,7 @@ >> #include <asm/compat.h> >> #include <asm/debug-monitors.h> >> #include <asm/pgtable.h> >> +#include <asm/syscall.h> >> #include <asm/traps.h> >> #include <asm/system_misc.h> >> >> @@ -1064,6 +1066,14 @@ asmlinkage int syscall_trace(int dir, struct pt_regs *regs) >> { >> unsigned long saved_reg; >> >> + if (dir) >> + audit_syscall_exit(regs); >> + else >> + audit_syscall_entry(syscall_get_arch(current, regs), >> + (int)regs->syscallno, >> + regs->orig_x0, regs->regs[1], >> + regs->regs[2], regs->regs[3]); >> + > > Do we really want to perform the audit checks before the tracehook calls? > Remember that the latter can rewrite all of the registers.
OK. I will change the code to make calls in the following order: On entry, *secure_computing *tracehook_report_syscall(ENTER) *trace_sys_enter *audit_syscall_entry On exit, *audit_syscall_exit *trace_sys_exit *tracehook_report_syscall(EXIT) The order here is the exact same as on x86, but such change might decrease the readability in syscall_trace().
Thanks, -Takahiro AKASHI
> Will >
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