This commit tests previous fix of bpf_probe_read_kernel_str().
The BPF helper bpf_probe_read_kernel_str should return -EFAULT when given a bad source pointer and the target buffer should only be modified to make the string NULL terminated.
bpf_probe_read_kernel_str() was previously inserting a NULL before the beginning of the dst buffer. This test should ensure that the implementation stays correct for now on.
Without the fix, this test will fail as follows: $ cd tools/testing/selftests/bpf $ make $ sudo ./test_progs --name=varlen ... test_varlen:FAIL:check got 0 != exp 66
Signed-off-by: Alban Crequy albancrequy@linux.microsoft.com Signed-off-by: Francis Laniel flaniel@linux.microsoft.com Acked-by: Yonghong Song yhs@fb.com
Changes v1 to v2: - add ack tag - fix my email - rebase on bpf tree and tag for bpf tree --- tools/testing/selftests/bpf/prog_tests/varlen.c | 7 +++++++ tools/testing/selftests/bpf/progs/test_varlen.c | 5 +++++ 2 files changed, 12 insertions(+)
diff --git a/tools/testing/selftests/bpf/prog_tests/varlen.c b/tools/testing/selftests/bpf/prog_tests/varlen.c index dd324b4933db..4d7056f8f177 100644 --- a/tools/testing/selftests/bpf/prog_tests/varlen.c +++ b/tools/testing/selftests/bpf/prog_tests/varlen.c @@ -63,6 +63,13 @@ void test_varlen(void) CHECK_VAL(data->total4, size1 + size2); CHECK(memcmp(data->payload4, exp_str, size1 + size2), "content_check", "doesn't match!\n"); + + CHECK_VAL(bss->ret_bad_read, -EFAULT); + CHECK_VAL(data->payload_bad[0], 0x42); + CHECK_VAL(data->payload_bad[1], 0x42); + CHECK_VAL(data->payload_bad[2], 0); + CHECK_VAL(data->payload_bad[3], 0x42); + CHECK_VAL(data->payload_bad[4], 0x42); cleanup: test_varlen__destroy(skel); } diff --git a/tools/testing/selftests/bpf/progs/test_varlen.c b/tools/testing/selftests/bpf/progs/test_varlen.c index 3987ff174f1f..20eb7d422c41 100644 --- a/tools/testing/selftests/bpf/progs/test_varlen.c +++ b/tools/testing/selftests/bpf/progs/test_varlen.c @@ -19,6 +19,7 @@ __u64 payload1_len1 = 0; __u64 payload1_len2 = 0; __u64 total1 = 0; char payload1[MAX_LEN + MAX_LEN] = {}; +__u64 ret_bad_read = 0;
/* .data */ int payload2_len1 = -1; @@ -36,6 +37,8 @@ int payload4_len2 = -1; int total4= -1; char payload4[MAX_LEN + MAX_LEN] = { 1 };
+char payload_bad[5] = { 0x42, 0x42, 0x42, 0x42, 0x42 }; + SEC("raw_tp/sys_enter") int handler64_unsigned(void *regs) { @@ -61,6 +64,8 @@ int handler64_unsigned(void *regs)
total1 = payload - (void *)payload1;
+ ret_bad_read = bpf_probe_read_kernel_str(payload_bad + 2, 1, (void *) -1); + return 0; }