linux-kernel - [PATCH] selftests/seccomp: Check CAP_SYS_ADMIN capability in the test mode_filter_without

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Date:   Sun, 31 Jul 2022 14:55:29 +0530
From:   Gautam Menghani <gautammenghani201@...il.com>
To:     keescook@...omium.org, shuah@...nel.org, brauner@...nel.org,
        paul.walmsley@...ive.com, palmer@...belt.com,
        aou@...s.berkeley.edu, guoren@...nel.org
Cc:     Gautam Menghani <gautammenghani201@...il.com>, luto@...capital.net,
        wad@...omium.org, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org,
        bpf@...r.kernel.org, linux-csky@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org
Subject: [PATCH] selftests/seccomp: Check CAP_SYS_ADMIN capability in the test mode_filter_without_nnp

In the "mode_filter_without_nnp" test in seccomp_bpf, there is currently
a TODO which asks to check the capability CAP_SYS_ADMIN instead of euid.
This patch adds support to check if the calling process has the flag 
CAP_SYS_ADMIN, and also if this flag has CAP_EFFECTIVE set.

Signed-off-by: Gautam Menghani <gautammenghani201@...il.com>
---
 tools/testing/selftests/seccomp/seccomp_bpf.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
index 136df5b76319..16b0edc520ef 100644
--- a/tools/testing/selftests/seccomp/seccomp_bpf.c
+++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
@@ -392,6 +392,8 @@ TEST(mode_filter_without_nnp)
 		.filter = filter,
 	};
 	long ret;
+	cap_t cap = cap_get_proc();
+	cap_flag_value_t is_cap_sys_admin = 0;
 
 	ret = prctl(PR_GET_NO_NEW_PRIVS, 0, NULL, 0, 0);
 	ASSERT_LE(0, ret) {
@@ -400,8 +402,8 @@ TEST(mode_filter_without_nnp)
 	errno = 0;
 	ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog, 0, 0);
 	/* Succeeds with CAP_SYS_ADMIN, fails without */
-	/* TODO(wad) check caps not euid */
-	if (geteuid()) {
+	cap_get_flag(cap, CAP_SYS_ADMIN, CAP_EFFECTIVE, &is_cap_sys_admin);
+	if (!is_cap_sys_admin) {
 		EXPECT_EQ(-1, ret);
 		EXPECT_EQ(EACCES, errno);
 	} else {
-- 
2.34.1