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x86/ptrace: run seccomp after ptrace 

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);