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x86/ptrace: run seccomp after ptrace

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This moves seccomp after ptrace on x86 to that seccomp can catch changes
made by ptrace. Emulation should skip the rest of processing too.

We can get rid of test_thread_flag because there's no longer any
opportunity for seccomp to mess with ptrace state before invoking
ptrace.

Suggested-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: x86@kernel.org
Cc: Andy Lutomirski <luto@kernel.org>
This commit is contained in:
Kees Cook 2016-06-09 12:36:50 -07:00
parent ce6526e8af
commit 93e35efb8d
1 changed files with 12 additions and 10 deletions
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22
arch/x86/entry/common.c
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@ -73,6 +73,7 @@ static long syscall_trace_enter(struct pt_regs *regs)
struct thread_info *ti = pt_regs_to_thread_info(regs);
unsigned long ret = 0;
bool emulated = false;
u32 work;
if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
@ -80,11 +81,19 @@ static long syscall_trace_enter(struct pt_regs *regs)
work = ACCESS_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY;
if (unlikely(work & _TIF_SYSCALL_EMU))
emulated = true;
if ((emulated || (work & _TIF_SYSCALL_TRACE)) &&
tracehook_report_syscall_entry(regs))
return -1L;
if (emulated)
return -1L;
#ifdef CONFIG_SECCOMP
/*
* Do seccomp first -- it should minimize exposure of other
* code, and keeping seccomp fast is probably more valuable
* than the rest of this.
* Do seccomp after ptrace, to catch any tracer changes.
*/
if (work & _TIF_SECCOMP) {
struct seccomp_data sd;
@ -117,13 +126,6 @@ static long syscall_trace_enter(struct pt_regs *regs)
}
#endif
if (unlikely(work & _TIF_SYSCALL_EMU))
ret = -1L;
if ((ret || test_thread_flag(TIF_SYSCALL_TRACE)) &&
tracehook_report_syscall_entry(regs))
ret = -1L;
if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
trace_sys_enter(regs, regs->orig_ax);