[LTP] [PATCH] Add test for CVE 2017-10661

[Richard Palethorpe]

Hello,

Looks mostly good, but see comments below.

Martin Doucha <mdoucha@suse.cz> writes:

> Signed-off-by: Martin Doucha <mdoucha@suse.cz>
> ---
>  testcases/cve/Makefile         |   3 +
>  testcases/cve/cve-2017-10661.c | 112 +++++++++++++++++++++++++++++++++
>  2 files changed, 115 insertions(+)
>  create mode 100644 testcases/cve/cve-2017-10661.c
>
> diff --git a/testcases/cve/Makefile b/testcases/cve/Makefile
> index da44fff60..1faee9fc5 100644
> --- a/testcases/cve/Makefile
> +++ b/testcases/cve/Makefile
> @@ -36,6 +36,9 @@ endif
>  cve-2017-2671:	CFLAGS += -pthread
>  cve-2017-2671:	LDLIBS += -lrt
>
> +cve-2017-10661:	CFLAGS += -pthread
> +cve-2017-10661:	LDLIBS += -lrt
> +
>  meltdown: CFLAGS += -I$(abs_srcdir)/../realtime/include
>
>  ifneq (,$(filter $(HOST_CPU),x86 x86_64))
> diff --git a/testcases/cve/cve-2017-10661.c b/testcases/cve/cve-2017-10661.c
> new file mode 100644
> index 000000000..6fe6b63c7
> --- /dev/null
> +++ b/testcases/cve/cve-2017-10661.c
> @@ -0,0 +1,112 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (C) 2020 SUSE LLC <mdoucha@suse.cz>
> + *
> + * CVE-2017-10661
> + *
> + * Test for race condition vulnerability in timerfd_settime(). Multiple
> + * concurrent calls of timerfd_settime() clearing the CANCEL_ON_SET flag may
> + * cause memory corruption. Fixed in:

We had some complaints that sorting tests by cve number made the tests
for a particular component difficult to find. So you should put this
with the other timerfd tests.

CVEs which rely on the interaction between many components or are
against hardware go in this folder.

> + *
> + *  commit 1e38da300e1e395a15048b0af1e5305bd91402f6
> + *  Author: Thomas Gleixner <tglx@linutronix.de>
> + *  Date:   Tue Jan 31 15:24:03 2017 +0100
> + *
> + *  timerfd: Protect the might cancel mechanism proper
> + */
> +#include <unistd.h>
> +#include <lapi/timerfd.h>
> +#include "tst_test.h"
> +#include "tst_fuzzy_sync.h"
> +#include "tst_taint.h"
> +
> +#define TIMERFD_FLAGS "timerfd_settime(TFD_TIMER_ABSTIME | TFD_TIMER_CANCEL_ON_SET)"
> +
> +#ifndef TFD_TIMER_CANCEL_ON_SET
> +#define TFD_TIMER_CANCEL_ON_SET (1<<1)
> +#endif
> +
> +static int fd = -1;
> +static struct itimerspec its;
> +static struct tst_fzsync_pair fzsync_pair;
> +
> +static void setup(void)
> +{
> +	int tmp;

All variables are temporary.

> +
> +	tst_taint_init(TST_TAINT_W | TST_TAINT_D);
> +	fd = timerfd_create(CLOCK_REALTIME, 0);
> +
> +	if (fd < 0) {
> +		tmp = (errno == ENOTSUP ? TCONF : TBROK) | TERRNO,

Huh? This compiles?

> +		tst_brk(tmp, "Cannot create timer");
> +	}
> +
> +	fzsync_pair.exec_loops = 1000000;
> +	tst_fzsync_pair_init(&fzsync_pair);
> +}
> +
> +static void cleanup(void)
> +{
> +	if (fd >= 0)
> +		SAFE_CLOSE(fd);
> +	tst_fzsync_pair_cleanup(&fzsync_pair);
> +}
> +
> +static int punch_clock(int flags)
> +{
> +	return timerfd_settime(fd, flags, &its, NULL);
> +}
> +
> +static void *thread_run(void *arg)
> +{
> +	while (tst_fzsync_run_b(&fzsync_pair)) {
> +		tst_fzsync_start_race_b(&fzsync_pair);
> +		// race to clear the CANCEL_ON_SET flag

We don't need inline comments to explain this. The code is clear
enough. Although it would be even clearer if you changed punch_clock to
set_clock_flags.

> +		punch_clock(0);
> +		tst_fzsync_end_race_b(&fzsync_pair);
> +	}
> +
> +	return arg;
> +}
> +
> +static void run(void)
> +{
> +	tst_fzsync_pair_reset(&fzsync_pair, thread_run);
> +
> +	while (tst_fzsync_run_a(&fzsync_pair)) {
> +		// set the CANCEL_ON_SET flag

Same here.
> +		TEST(punch_clock(TFD_TIMER_ABSTIME | TFD_TIMER_CANCEL_ON_SET));
> +
> +		if (TST_RET == -1)
> +			tst_res(TBROK | TTERRNO, TIMERFD_FLAGS " failed");
> +
> +		if (TST_RET != 0)
> +			tst_res(TBROK | TTERRNO, "Invalid " TIMERFD_FLAGS
> +				" return value");
> +
> +		tst_fzsync_start_race_a(&fzsync_pair);
> +		// race to clear the CANCEL_ON_SET flag

and here.
> +		punch_clock(0);
> +		tst_fzsync_end_race_a(&fzsync_pair);
> +
> +		if (tst_taint_check()) {
> +			tst_res(TFAIL, "Kernel is vulnerable");
> +			return;
> +		}
> +	}
> +
> +	tst_res(TPASS, "Nothing bad happened, probably");
> +}
> +
> +static struct tst_test test = {
> +	.test_all = run,
> +	.setup = setup,
> +	.cleanup = cleanup,
> +	.min_kver = "2.6.25",
> +	.tags = (const struct tst_tag[]) {
> +		{"linux-git", "1e38da300e1e"},
> +		{"CVE", "2017-10661"},
> +		{}
> +	}
> +};
> --
> 2.25.0


--
Thank you,
Richard.