bpf: Disallow bpf programs call prog_run command.

The verifier cannot perform sufficient validation of bpf_attr->test.ctx_in
pointer, therefore bpf programs should not be allowed to call BPF_PROG_RUN
command from within the program.
To fix this issue split bpf_sys_bpf() bpf helper into normal kern_sys_bpf()
kernel function that can only be used by the kernel light skeleton directly.

Reported-by: YiFei Zhu <zhuyifei@google.com>
Fixes: b1d18a7574d0 ("bpf: Extend sys_bpf commands for bpf_syscall programs.")
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 7dc3f80..a1cb0bd 100644 (file)
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -5071,9 +5071,6 @@ static bool syscall_prog_is_valid_access(int off, int size,
 
 BPF_CALL_3(bpf_sys_bpf, int, cmd, union bpf_attr *, attr, u32, attr_size)
 {
-       struct bpf_prog * __maybe_unused prog;
-       struct bpf_tramp_run_ctx __maybe_unused run_ctx;
-
        switch (cmd) {
        case BPF_MAP_CREATE:
        case BPF_MAP_UPDATE_ELEM:
@@ -5083,6 +5080,18 @@ BPF_CALL_3(bpf_sys_bpf, int, cmd, union bpf_attr *, attr, u32, attr_size)
        case BPF_LINK_CREATE:
        case BPF_RAW_TRACEPOINT_OPEN:
                break;
+       default:
+               return -EINVAL;
+       }
+       return __sys_bpf(cmd, KERNEL_BPFPTR(attr), attr_size);
+}
+
+int kern_sys_bpf(int cmd, union bpf_attr *attr, unsigned int size)
+{
+       struct bpf_prog * __maybe_unused prog;
+       struct bpf_tramp_run_ctx __maybe_unused run_ctx;
+
+       switch (cmd) {
 #ifdef CONFIG_BPF_JIT /* __bpf_prog_enter_sleepable used by trampoline and JIT */
        case BPF_PROG_TEST_RUN:
                if (attr->test.data_in || attr->test.data_out ||
@@ -5113,11 +5122,10 @@ BPF_CALL_3(bpf_sys_bpf, int, cmd, union bpf_attr *, attr, u32, attr_size)
                return 0;
 #endif
        default:
-               return -EINVAL;
+               return ____bpf_sys_bpf(cmd, attr, size);
        }
-       return __sys_bpf(cmd, KERNEL_BPFPTR(attr), attr_size);
 }
-EXPORT_SYMBOL(bpf_sys_bpf);
+EXPORT_SYMBOL(kern_sys_bpf);
 
 static const struct bpf_func_proto bpf_sys_bpf_proto = {
        .func           = bpf_sys_bpf,

diff --git a/tools/lib/bpf/skel_internal.h b/tools/lib/bpf/skel_internal.h
index bd6f450..70adf7b 100644 (file)
--- a/tools/lib/bpf/skel_internal.h
+++ b/tools/lib/bpf/skel_internal.h
@@ -66,13 +66,13 @@ struct bpf_load_and_run_opts {
        const char *errstr;
 };
 
-long bpf_sys_bpf(__u32 cmd, void *attr, __u32 attr_size);
+long kern_sys_bpf(__u32 cmd, void *attr, __u32 attr_size);
 
 static inline int skel_sys_bpf(enum bpf_cmd cmd, union bpf_attr *attr,
                          unsigned int size)
 {
 #ifdef __KERNEL__
-       return bpf_sys_bpf(cmd, attr, size);
+       return kern_sys_bpf(cmd, attr, size);
 #else
        return syscall(__NR_bpf, cmd, attr, size);
 #endif