[LTP] [PATCH v4] syscalls/prctl04: Fix false positive report when SECCOMP_MODE_FILTER is not supported

[xuyang2018.jy@fujitsu.com]

Hi He


> The child process expectedly should not receive the expected siganl, SIGSYS,
> when kernel does not support SECCOMP_MODE_FILTER. The original verify_prctl
> does not realize it and gives a FAIL for not receiving the signal.
> 
> This patch tests if SECCOMP_MODE_FILTER is supported in setup and adds a
> variable to record it and to inform verify_prctl later to skip the case.
> 
> Before this patch:
> root@xilinx-zynq:~# /opt/ltp/testcases/bin/prctl04
> tst_test.c:1431: TINFO: Timeout per run is 0h 05m 00s
> prctl04.c:221: TINFO: kernel support PR_GET/SET_SECCOMP
> prctl04.c:132: TPASS: prctl(PR_SET_SECCOMP) sets SECCOMP_MODE_STRICT succeed
> prctl04.c:205: TPASS: SECCOMP_MODE_STRICT doesn't permit GET_SECCOMP call
> prctl04.c:140: TPASS: SECCOMP_MODE_STRICT permits read(2) write(2) and _exit(2)
> prctl04.c:205: TPASS: SECCOMP_MODE_STRICT doesn't permit close(2)
> prctl04.c:162: TCONF: kernel doesn't support SECCOMP_MODE_FILTER
> prctl04.c:162: TCONF: kernel doesn't support SECCOMP_MODE_FILTER
> prctl04.c:162: TCONF: kernel doesn't support SECCOMP_MODE_FILTER
> prctl04.c:212: TFAIL: SECCOMP_MODE_FILTER permits exit() unexpectedly
> prctl04.c:162: 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
> prctl04.c:225: TINFO: kernel supports PR_GET/SET_SECCOMP
> prctl04.c:135: TPASS: prctl(PR_SET_SECCOMP) sets SECCOMP_MODE_STRICT succeed
> prctl04.c:209: TPASS: SECCOMP_MODE_STRICT doesn't permit GET_SECCOMP call
> prctl04.c:143: TPASS: SECCOMP_MODE_STRICT permits read(2) write(2) and _exit(2)
> prctl04.c:209: TPASS: SECCOMP_MODE_STRICT doesn't permit close(2)
> prctl04.c:161: TCONF: kernel doesn't support SECCOMP_MODE_FILTER
> prctl04.c:161: TCONF: kernel doesn't support SECCOMP_MODE_FILTER
> prctl04.c:161: TCONF: kernel doesn't support SECCOMP_MODE_FILTER
> prctl04.c:161: TCONF: kernel doesn't support SECCOMP_MODE_FILTER
> 
> Fixes: 3ddc217d7 ("syscalls/prctl04.c: New test for prctl() with PR_{SET,GET}_SECCOMP:)
> 
> Signed-off-by: He Zhe <zhe.he@windriver.com>
> Reviewed-by: Yang Xu <xuyang2018.jy@fujitsu.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
> v4: Update commit log, judge mode_filter_not_supported first
> 
>   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 (tc->pass_flag == 2 && mode_filter_not_supported == 0)
>   			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;
> +			}

I use "TST_RET == -1 && TST_ERR == EINVAL" instead, then merged.
Thanks for this fix.

Best Regards
Yang Xu
> +
> +		tst_res(TINFO, "kernel supports SECCOMP_MODE_FILTER");
> +
>   		return;
>   	}
>