Messages in this thread Patch in this message | | | From | Will Drewry <> | Subject | [PATCH v11 11/12] x86: Enable HAVE_ARCH_SECCOMP_FILTER | Date | Fri, 24 Feb 2012 21:21:50 -0600 |
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Enable support for seccomp filter on x86: - asm/tracehook.h exists - syscall_get_arguments() works - syscall_rollback() works - ptrace_report_syscall() works - secure_computing() return value is honored (see below)
This also adds support for honoring the return value from secure_computing().
SECCOMP_RET_TRACE and SECCOMP_RET_TRAP may result in seccomp needing to skip a system call without killing the process. This is done by returning a non-zero (-1) value from secure_computing. This change makes x86 respect that return value.
To ensure that minimal kernel code is exposed, a non-zero return value results in an immediate return to user space (with an invalid syscall number).
Signed-off-by: Will Drewry <wad@chromium.org> --- arch/x86/Kconfig | 1 + arch/x86/kernel/ptrace.c | 7 ++++++- 2 files changed, 7 insertions(+), 1 deletions(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 5bed94e..4c9012b 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -82,6 +82,7 @@ config X86 select CLKEVT_I8253 select ARCH_HAVE_NMI_SAFE_CMPXCHG select GENERIC_IOMAP + select HAVE_ARCH_SECCOMP_FILTER config INSTRUCTION_DECODER def_bool (KPROBES || PERF_EVENTS) diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c index 5026738..90d465a 100644 --- a/arch/x86/kernel/ptrace.c +++ b/arch/x86/kernel/ptrace.c @@ -1380,7 +1380,11 @@ long syscall_trace_enter(struct pt_regs *regs) regs->flags |= X86_EFLAGS_TF; /* do the secure computing check first */ - secure_computing(regs->orig_ax); + if (secure_computing(regs->orig_ax)) { + /* seccomp failures shouldn't expose any additional code. */ + ret = -1L; + goto out; + } if (unlikely(test_thread_flag(TIF_SYSCALL_EMU))) ret = -1L; @@ -1405,6 +1409,7 @@ long syscall_trace_enter(struct pt_regs *regs) regs->dx, regs->r10); #endif +out: return ret ?: regs->orig_ax; } -- 1.7.5.4
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