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Message-ID: <201906271030.C30D8CDEDA@keescook>
Date: Thu, 27 Jun 2019 10:30:30 -0700
From: Kees Cook <keescook@...omium.org>
To: Andy Lutomirski <luto@...nel.org>
Cc: x86@...nel.org, LKML <linux-kernel@...r.kernel.org>,
Florian Weimer <fweimer@...hat.com>, Jann Horn <jannh@...gle.com>,
Borislav Petkov <bp@...en8.de>,
Kernel Hardening <kernel-hardening@...ts.openwall.com>,
Peter Zijlstra <peterz@...radead.org>,
Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v2 8/8] selftests/x86: Add a test for process_vm_readv()
on the vsyscall page
On Wed, Jun 26, 2019 at 09:45:09PM -0700, Andy Lutomirski wrote:
> get_gate_page() is a piece of somewhat alarming code to make
> get_user_pages() work on the vsyscall page. Test it via
> process_vm_readv().
>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: Kernel Hardening <kernel-hardening@...ts.openwall.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Signed-off-by: Andy Lutomirski <luto@...nel.org>
Reviewed-by: Kees Cook <keescook@...omium.org>
-Kees
> ---
> tools/testing/selftests/x86/test_vsyscall.c | 35 +++++++++++++++++++++
> 1 file changed, 35 insertions(+)
>
> diff --git a/tools/testing/selftests/x86/test_vsyscall.c b/tools/testing/selftests/x86/test_vsyscall.c
> index 34a1d35995ef..4602326b8f5b 100644
> --- a/tools/testing/selftests/x86/test_vsyscall.c
> +++ b/tools/testing/selftests/x86/test_vsyscall.c
> @@ -18,6 +18,7 @@
> #include <sched.h>
> #include <stdbool.h>
> #include <setjmp.h>
> +#include <sys/uio.h>
>
> #ifdef __x86_64__
> # define VSYS(x) (x)
> @@ -459,6 +460,38 @@ static int test_vsys_x(void)
> return 0;
> }
>
> +static int test_process_vm_readv(void)
> +{
> +#ifdef __x86_64__
> + char buf[4096];
> + struct iovec local, remote;
> + int ret;
> +
> + printf("[RUN]\tprocess_vm_readv() from vsyscall page\n");
> +
> + local.iov_base = buf;
> + local.iov_len = 4096;
> + remote.iov_base = (void *)0xffffffffff600000;
> + remote.iov_len = 4096;
> + ret = process_vm_readv(getpid(), &local, 1, &remote, 1, 0);
> + if (ret != 4096) {
> + printf("[OK]\tprocess_vm_readv() failed (ret = %d, errno = %d)\n", ret, errno);
> + return 0;
> + }
> +
> + if (vsyscall_map_r) {
> + if (!memcmp(buf, (const void *)0xffffffffff600000, 4096)) {
> + printf("[OK]\tIt worked and read correct data\n");
> + } else {
> + printf("[FAIL]\tIt worked but returned incorrect data\n");
> + return 1;
> + }
> + }
> +#endif
> +
> + return 0;
> +}
> +
> #ifdef __x86_64__
> #define X86_EFLAGS_TF (1UL << 8)
> static volatile sig_atomic_t num_vsyscall_traps;
> @@ -533,6 +566,8 @@ int main(int argc, char **argv)
> nerrs += test_vsys_r();
> nerrs += test_vsys_x();
>
> + nerrs += test_process_vm_readv();
> +
> #ifdef __x86_64__
> nerrs += test_emulation();
> #endif
> --
> 2.21.0
>
--
Kees Cook
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