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Message-Id: <1331781125-15658-13-git-send-email-wad@chromium.org>
Date: Wed, 14 Mar 2012 22:12:04 -0500
From: Will Drewry <wad@...omium.org>
To: linux-kernel@...r.kernel.org
Cc: linux-arch@...r.kernel.org,
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Will Drewry <wad@...omium.org>
Subject: [PATCH v15 12/13] x86: Enable HAVE_ARCH_SECCOMP_FILTER
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@...omium.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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