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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id n12sm5822899pgk.20.2020.09.19.01.06.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 19 Sep 2020 01:06:45 -0700 (PDT) From: Kees Cook To: linux-kernel@vger.kernel.org Cc: Kees Cook , Thadeu Lima de Souza Cascardo , Max Filippov , Michael Ellerman , Christian Brauner , Andy Lutomirski , Will Drewry , linux-kselftest@vger.kernel.org, linux-mips@vger.kernel.org, linux-xtensa@linux-xtensa.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org Subject: [PATCH v2 2/4] selftests/seccomp: Allow syscall nr and ret value to be set separately Date: Sat, 19 Sep 2020 01:06:35 -0700 Message-Id: <20200919080637.259478-3-keescook@chromium.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200919080637.259478-1-keescook@chromium.org> References: <20200919080637.259478-1-keescook@chromium.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org In preparation for setting syscall nr and ret values separately, refactor the helpers to take a pointer to a value, so that a NULL can indicate "do not change this respective value". This is done to keep the regset read/write happening once and in one code path. Signed-off-by: Kees Cook Acked-by: Christian Brauner --- tools/testing/selftests/seccomp/seccomp_bpf.c | 59 +++++++++++++++---- 1 file changed, 47 insertions(+), 12 deletions(-) diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c index c0311b4c736b..98ce5e8a6398 100644 --- a/tools/testing/selftests/seccomp/seccomp_bpf.c +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c @@ -1888,27 +1888,47 @@ int get_syscall(struct __test_metadata *_metadata, pid_t tracee) } /* Architecture-specific syscall changing routine. */ -void change_syscall(struct __test_metadata *_metadata, - pid_t tracee, int syscall, int result) +void __change_syscall(struct __test_metadata *_metadata, + pid_t tracee, long *syscall, long *ret) { ARCH_REGS orig, regs; + /* Do not get/set registers if we have nothing to do. */ + if (!syscall && !ret) + return; + EXPECT_EQ(0, ARCH_GETREGS(regs)) { return; } orig = regs; - SYSCALL_NUM_SET(regs, syscall); + if (syscall) + SYSCALL_NUM_SET(regs, *syscall); - /* If syscall is skipped, change return value. */ - if (syscall == -1) - SYSCALL_RET_SET(regs, result); + if (ret) + SYSCALL_RET_SET(regs, *ret); /* Flush any register changes made. */ if (memcmp(&orig, ®s, sizeof(orig)) != 0) EXPECT_EQ(0, ARCH_SETREGS(regs)); } +/* Change only syscall number. */ +void change_syscall_nr(struct __test_metadata *_metadata, + pid_t tracee, long syscall) +{ + __change_syscall(_metadata, tracee, &syscall, NULL); +} + +/* Change syscall return value (and set syscall number to -1). */ +void change_syscall_ret(struct __test_metadata *_metadata, + pid_t tracee, long ret) +{ + long syscall = -1; + + __change_syscall(_metadata, tracee, &syscall, &ret); +} + void tracer_seccomp(struct __test_metadata *_metadata, pid_t tracee, int status, void *args) { @@ -1924,17 +1944,17 @@ void tracer_seccomp(struct __test_metadata *_metadata, pid_t tracee, case 0x1002: /* change getpid to getppid. */ EXPECT_EQ(__NR_getpid, get_syscall(_metadata, tracee)); - change_syscall(_metadata, tracee, __NR_getppid, 0); + change_syscall_nr(_metadata, tracee, __NR_getppid); break; case 0x1003: /* skip gettid with valid return code. */ EXPECT_EQ(__NR_gettid, get_syscall(_metadata, tracee)); - change_syscall(_metadata, tracee, -1, 45000); + change_syscall_ret(_metadata, tracee, 45000); break; case 0x1004: /* skip openat with error. */ EXPECT_EQ(__NR_openat, get_syscall(_metadata, tracee)); - change_syscall(_metadata, tracee, -1, -ESRCH); + change_syscall_ret(_metadata, tracee, -ESRCH); break; case 0x1005: /* do nothing (allow getppid) */ @@ -1961,6 +1981,8 @@ void tracer_ptrace(struct __test_metadata *_metadata, pid_t tracee, int ret; unsigned long msg; static bool entry; + long syscall_nr_val, syscall_ret_val; + long *syscall_nr = NULL, *syscall_ret = NULL; FIXTURE_DATA(TRACE_syscall) *self = args; /* @@ -1987,17 +2009,30 @@ void tracer_ptrace(struct __test_metadata *_metadata, pid_t tracee, else return; + syscall_nr = &syscall_nr_val; + syscall_ret = &syscall_ret_val; + + /* Now handle the actual rewriting cases. */ switch (self->syscall_nr) { case __NR_getpid: - change_syscall(_metadata, tracee, __NR_getppid, 0); + syscall_nr_val = __NR_getppid; + /* Never change syscall return for this case. */ + syscall_ret = NULL; break; case __NR_gettid: - change_syscall(_metadata, tracee, -1, 45000); + syscall_nr_val = -1; + syscall_ret_val = 45000; break; case __NR_openat: - change_syscall(_metadata, tracee, -1, -ESRCH); + syscall_nr_val = -1; + syscall_ret_val = -ESRCH; break; + default: + /* Unhandled, do nothing. */ + return; } + + __change_syscall(_metadata, tracee, syscall_nr, syscall_ret); } FIXTURE_VARIANT(TRACE_syscall) {