[LTP] [PATCH v3] syscalls/prctl04: Fix false positive report when SECCOMP_MODE_FILTER is not supported

[xuyang2018.jy@fujitsu.com]

Hi He

> The child process really should not receive the expected siganl, SIGSYS, when
> kernel doesn't support SECCOMP_MODE_FILTER.
I still feel confused, so which subtestcase has problem since we have do 
check whether support SECCOMP_MODE_FILTER in check_filter_mode.
> 
> This patch tests if SECCOMP_MODE_FILTER is supported in setup and adds a
> variable to record it.
> 
> Before this patch:
> root@xilinx-zynq:~# /opt/ltp/testcases/bin/prctl04
> tst_test.c:1431: TINFO: Timeout per run is 0h 05m 00s
> ---- snip ----
> prctl04.c:154: TCONF: kernel doesn't support SECCOMP_MODE_FILTER
> prctl04.c:154: TCONF: kernel doesn't support SECCOMP_MODE_FILTER
> prctl04.c:154: TCONF: kernel doesn't support SECCOMP_MODE_FILTER
> prctl04.c:204: TFAIL: SECCOMP_MODE_FILTER permits exit() unexpectedly
> prctl04.c:154: TCONF: kernel doesn't support SECCOMP_MODE_FILTER
> 
> After this patch:
> root@xilinx-zynq:~# /opt/ltp/testcases/bin/prctl04
> tst_test.c:1431: TINFO: Timeout per run is 0h 05m 00s
> ---- snip ----
> prctl04.c:154: TCONF: kernel doesn't support SECCOMP_MODE_FILTER
> prctl04.c:154: TCONF: kernel doesn't support SECCOMP_MODE_FILTER
> prctl04.c:154: TCONF: kernel doesn't support SECCOMP_MODE_FILTER
> prctl04.c:154: TCONF: kernel doesn't support SECCOMP_MODE_FILTER


The line 154 and 204 is refer to origin case[1], so do you use the 
lastest ltp?

[1] 
https://github.com/linux-test-project/ltp/commit/3ddc217d7b466f16782c257e29e18b251969edec#diff-6ae2f0e9ae152457424103cc20b7885e242f33f58b2e543b7941671f418d9485R154

Best Regards
Yang Xu
> 
> Signed-off-by: He Zhe <zhe.he@windriver.com>
> ---
> v2: Add a variable to record the support status instead of exit(1)
> v3: Move mode_filter_not_supported check a bit upper to save a prctl call
> 
>   testcases/kernel/syscalls/prctl/prctl04.c | 30 +++++++++++++++++------
>   1 file changed, 22 insertions(+), 8 deletions(-)
> 
> diff --git a/testcases/kernel/syscalls/prctl/prctl04.c b/testcases/kernel/syscalls/prctl/prctl04.c
> index b9f4c2a10..d3de4b0d6 100644
> --- a/testcases/kernel/syscalls/prctl/prctl04.c
> +++ b/testcases/kernel/syscalls/prctl/prctl04.c
> @@ -93,6 +93,9 @@ static struct tcase {
>   	"SECCOMP_MODE_FILTER doesn't permit exit()"}
>   };
>   
> +
> +static int mode_filter_not_supported;
> +
>   static void check_filter_mode_inherit(void)
>   {
>   	int childpid;
> @@ -154,16 +157,17 @@ static void check_filter_mode(int val)
>   {
>   	int fd;
>   
> +	if (mode_filter_not_supported == 1) {
> +		tst_res(TCONF, "kernel doesn't support SECCOMP_MODE_FILTER");
> +		return;
> +	}
> +
>   	fd = SAFE_OPEN(FNAME, O_RDWR | O_CREAT, 0666);
>   
>   	TEST(prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &strict));
>   	if (TST_RET == -1) {
> -		if (TST_ERR == EINVAL)
> -			tst_res(TCONF,
> -				"kernel doesn't support SECCOMP_MODE_FILTER");
> -		else
> -			tst_res(TFAIL | TERRNO,
> -				"prctl(PR_SET_SECCOMP) sets SECCOMP_MODE_FILTER failed");
> +		tst_res(TFAIL | TERRNO,
> +			"prctl(PR_SET_SECCOMP) sets SECCOMP_MODE_FILTER failed");
>   		return;
>   	}
>   
> @@ -208,7 +212,7 @@ static void verify_prctl(unsigned int n)
>   			return;
>   		}
>   
> -		if (tc->pass_flag == 2)
> +		if (mode_filter_not_supported == 0 && tc->pass_flag == 2)
>   			tst_res(TFAIL,
>   				"SECCOMP_MODE_FILTER permits exit() unexpectedly");
>   	}
> @@ -218,7 +222,17 @@ static void setup(void)
>   {
>   	TEST(prctl(PR_GET_SECCOMP));
>   	if (TST_RET == 0) {
> -		tst_res(TINFO, "kernel support PR_GET/SET_SECCOMP");
> +		tst_res(TINFO, "kernel supports PR_GET/SET_SECCOMP");
> +
> +		TEST(prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, NULL));
> +		if (TST_RET == -1)
> +			if (TST_ERR == EINVAL) {
> +				mode_filter_not_supported = 1;
> +				return;
> +			}
> +
> +		tst_res(TINFO, "kernel supports SECCOMP_MODE_FILTER");
> +
>   		return;
>   	}
>