selftests/bpf: Test narrow load from bpf_sysctl.write
There are tests for full and narrows loads from bpf_sysctl.file_pos, but
for bpf_sysctl.write only full load is tested. Add the missing test.
Suggested-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrey Ignatov <rdna@fb.com>
Link: https://lore.kernel.org/bpf/20191029143027.28681-1-iii@linux.ibm.com
diff --git a/tools/testing/selftests/bpf/test_sysctl.c b/tools/testing/selftests/bpf/test_sysctl.c
index a320e38..7aff907 100644
--- a/tools/testing/selftests/bpf/test_sysctl.c
+++ b/tools/testing/selftests/bpf/test_sysctl.c
@@ -121,6 +121,29 @@ static struct sysctl_test tests[] = {
.result = OP_EPERM,
},
{
+ .descr = "ctx:write sysctl:write read ok narrow",
+ .insns = {
+ /* u64 w = (u16)write & 1; */
+#if __BYTE_ORDER == __LITTLE_ENDIAN
+ BPF_LDX_MEM(BPF_H, BPF_REG_7, BPF_REG_1,
+ offsetof(struct bpf_sysctl, write)),
+#else
+ BPF_LDX_MEM(BPF_H, BPF_REG_7, BPF_REG_1,
+ offsetof(struct bpf_sysctl, write) + 2),
+#endif
+ BPF_ALU64_IMM(BPF_AND, BPF_REG_7, 1),
+ /* return 1 - w; */
+ BPF_MOV64_IMM(BPF_REG_0, 1),
+ BPF_ALU64_REG(BPF_SUB, BPF_REG_0, BPF_REG_7),
+ BPF_EXIT_INSN(),
+ },
+ .attach_type = BPF_CGROUP_SYSCTL,
+ .sysctl = "kernel/domainname",
+ .open_flags = O_WRONLY,
+ .newval = "(none)", /* same as default, should fail anyway */
+ .result = OP_EPERM,
+ },
+ {
.descr = "ctx:write sysctl:read write reject",
.insns = {
/* write = X */