bpf: fix bpf_tail_call() x64 JIT

[ upstream commit 90caccdd8cc0215705f18b92771b449b01e2474a ]

- bpf prog_array just like all other types of bpf array accepts 32-bit index.
  Clarify that in the comment.
- fix x64 JIT of bpf_tail_call which was incorrectly loading 8 instead of 4 bytes
- tighten corresponding check in the interpreter to stay consistent

The JIT bug can be triggered after introduction of BPF_F_NUMA_NODE flag
in commit 96eabe7a40aa in 4.14. Before that the map_flags would stay zero and
though JIT code is wrong it will check bounds correctly.
Hence two fixes tags. All other JITs don't have this problem.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Fixes: 96eabe7a40aa ("bpf: Allow selecting numa node during map creation")
Fixes: b52f00e6a715 ("x86: bpf_jit: implement bpf_tail_call() helper")
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 33f002e..33c42b8 100644 (file)
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -266,9 +266,9 @@ static void emit_bpf_tail_call(u8 **pprog)
        /* if (index >= array->map.max_entries)
         *   goto out;
         */
-       EMIT4(0x48, 0x8B, 0x46,                   /* mov rax, qword ptr [rsi + 16] */
+       EMIT2(0x89, 0xD2);                        /* mov edx, edx */
+       EMIT3(0x39, 0x56,                         /* cmp dword ptr [rsi + 16], edx */
              offsetof(struct bpf_array, map.max_entries));
-       EMIT3(0x48, 0x39, 0xD0);                  /* cmp rax, rdx */
 #define OFFSET1 43 /* number of bytes to jump */
        EMIT2(X86_JBE, OFFSET1);                  /* jbe out */
        label1 = cnt;

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 3fd76cf..e54ea31 100644 (file)
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -517,7 +517,7 @@ select_insn:
                struct bpf_map *map = (struct bpf_map *) (unsigned long) BPF_R2;
                struct bpf_array *array = container_of(map, struct bpf_array, map);
                struct bpf_prog *prog;
-               u64 index = BPF_R3;
+               u32 index = BPF_R3;
 
                if (unlikely(index >= array->map.max_entries))
                        goto out;