4.20-stable review patch. If anyone has any objections, please let me know.
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From: Kees Cook keescook@chromium.org
commit ed5f13261cb65b02c611ae9971677f33581d4286 upstream.
Passing EPERM during syscall skipping was confusing since the test wasn't actually exercising the errno evaluation -- it was just passing a literal "1" (EPERM). Instead, expand the tests to check both direct value returns (positive, 45000 in this case), and errno values (negative, -ESRCH in this case) to check both fake success and fake failure during syscall skipping.
Reported-by: Colin Ian King colin.king@canonical.com Fixes: a33b2d0359a0 ("selftests/seccomp: Add tests for basic ptrace actions") Cc: stable@vger.kernel.org Signed-off-by: Kees Cook keescook@chromium.org Signed-off-by: Shuah Khan shuah@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- tools/testing/selftests/seccomp/seccomp_bpf.c | 72 ++++++++++++++++++++------ 1 file changed, 57 insertions(+), 15 deletions(-)
--- a/tools/testing/selftests/seccomp/seccomp_bpf.c +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c @@ -1563,7 +1563,16 @@ TEST_F(TRACE_poke, getpid_runs_normally) #ifdef SYSCALL_NUM_RET_SHARE_REG # define EXPECT_SYSCALL_RETURN(val, action) EXPECT_EQ(-1, action) #else -# define EXPECT_SYSCALL_RETURN(val, action) EXPECT_EQ(val, action) +# define EXPECT_SYSCALL_RETURN(val, action) \ + do { \ + errno = 0; \ + if (val < 0) { \ + EXPECT_EQ(-1, action); \ + EXPECT_EQ(-(val), errno); \ + } else { \ + EXPECT_EQ(val, action); \ + } \ + } while (0) #endif
/* Use PTRACE_GETREGS and PTRACE_SETREGS when available. This is useful for @@ -1602,7 +1611,7 @@ int get_syscall(struct __test_metadata *
/* Architecture-specific syscall changing routine. */ void change_syscall(struct __test_metadata *_metadata, - pid_t tracee, int syscall) + pid_t tracee, int syscall, int result) { int ret; ARCH_REGS regs; @@ -1661,7 +1670,7 @@ void change_syscall(struct __test_metada #ifdef SYSCALL_NUM_RET_SHARE_REG TH_LOG("Can't modify syscall return on this architecture"); #else - regs.SYSCALL_RET = EPERM; + regs.SYSCALL_RET = result; #endif
#ifdef HAVE_GETREGS @@ -1689,14 +1698,19 @@ void tracer_syscall(struct __test_metada case 0x1002: /* change getpid to getppid. */ EXPECT_EQ(__NR_getpid, get_syscall(_metadata, tracee)); - change_syscall(_metadata, tracee, __NR_getppid); + change_syscall(_metadata, tracee, __NR_getppid, 0); break; case 0x1003: - /* skip gettid. */ + /* skip gettid with valid return code. */ EXPECT_EQ(__NR_gettid, get_syscall(_metadata, tracee)); - change_syscall(_metadata, tracee, -1); + change_syscall(_metadata, tracee, -1, 45000); break; case 0x1004: + /* skip openat with error. */ + EXPECT_EQ(__NR_openat, get_syscall(_metadata, tracee)); + change_syscall(_metadata, tracee, -1, -ESRCH); + break; + case 0x1005: /* do nothing (allow getppid) */ EXPECT_EQ(__NR_getppid, get_syscall(_metadata, tracee)); break; @@ -1729,9 +1743,11 @@ void tracer_ptrace(struct __test_metadat nr = get_syscall(_metadata, tracee);
if (nr == __NR_getpid) - change_syscall(_metadata, tracee, __NR_getppid); + change_syscall(_metadata, tracee, __NR_getppid, 0); + if (nr == __NR_gettid) + change_syscall(_metadata, tracee, -1, 45000); if (nr == __NR_openat) - change_syscall(_metadata, tracee, -1); + change_syscall(_metadata, tracee, -1, -ESRCH); }
FIXTURE_DATA(TRACE_syscall) { @@ -1748,8 +1764,10 @@ FIXTURE_SETUP(TRACE_syscall) BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_TRACE | 0x1002), BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_gettid, 0, 1), BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_TRACE | 0x1003), - BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_getppid, 0, 1), + BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_openat, 0, 1), BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_TRACE | 0x1004), + BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_getppid, 0, 1), + BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_TRACE | 0x1005), BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW), };
@@ -1797,15 +1815,26 @@ TEST_F(TRACE_syscall, ptrace_syscall_red EXPECT_NE(self->mypid, syscall(__NR_getpid)); }
-TEST_F(TRACE_syscall, ptrace_syscall_dropped) +TEST_F(TRACE_syscall, ptrace_syscall_errno) +{ + /* Swap SECCOMP_RET_TRACE tracer for PTRACE_SYSCALL tracer. */ + teardown_trace_fixture(_metadata, self->tracer); + self->tracer = setup_trace_fixture(_metadata, tracer_ptrace, NULL, + true); + + /* Tracer should skip the open syscall, resulting in ESRCH. */ + EXPECT_SYSCALL_RETURN(-ESRCH, syscall(__NR_openat)); +} + +TEST_F(TRACE_syscall, ptrace_syscall_faked) { /* Swap SECCOMP_RET_TRACE tracer for PTRACE_SYSCALL tracer. */ teardown_trace_fixture(_metadata, self->tracer); self->tracer = setup_trace_fixture(_metadata, tracer_ptrace, NULL, true);
- /* Tracer should skip the open syscall, resulting in EPERM. */ - EXPECT_SYSCALL_RETURN(EPERM, syscall(__NR_openat)); + /* Tracer should skip the gettid syscall, resulting fake pid. */ + EXPECT_SYSCALL_RETURN(45000, syscall(__NR_gettid)); }
TEST_F(TRACE_syscall, syscall_allowed) @@ -1838,7 +1867,21 @@ TEST_F(TRACE_syscall, syscall_redirected EXPECT_NE(self->mypid, syscall(__NR_getpid)); }
-TEST_F(TRACE_syscall, syscall_dropped) +TEST_F(TRACE_syscall, syscall_errno) +{ + long ret; + + ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0); + ASSERT_EQ(0, ret); + + ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->prog, 0, 0); + ASSERT_EQ(0, ret); + + /* openat has been skipped and an errno return. */ + EXPECT_SYSCALL_RETURN(-ESRCH, syscall(__NR_openat)); +} + +TEST_F(TRACE_syscall, syscall_faked) { long ret;
@@ -1849,8 +1892,7 @@ TEST_F(TRACE_syscall, syscall_dropped) ASSERT_EQ(0, ret);
/* gettid has been skipped and an altered return value stored. */ - EXPECT_SYSCALL_RETURN(EPERM, syscall(__NR_gettid)); - EXPECT_NE(self->mytid, syscall(__NR_gettid)); + EXPECT_SYSCALL_RETURN(45000, syscall(__NR_gettid)); }
TEST_F(TRACE_syscall, skip_after_RET_TRACE)