bpf: fix bpf_tail_call() x64 JIT

- 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 <[email protected]>
Fixes: 96eabe7a40aa ("bpf: Allow selecting numa node during map creation")
Fixes: b52f00e6a715 ("x86: bpf_jit: implement bpf_tail_call() helper")
Acked-by: Daniel Borkmann <[email protected]>
Acked-by: Martin KaFai Lau <[email protected]>
Reviewed-by: Eric Dumazet <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 8c9573660d51e6b0297e4464b3af2056d93b9f3c..0554e8aef4d54522393f78b8b7973f8dfac4750c 100644 (file)
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -284,9 +284,9 @@ 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/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 43ab5c402f98f3c2dc15ccc49ec475530a39e401..f90860d1f8979e03b10063a04179bed44c137e5a 100644 (file)
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -312,7 +312,7 @@ union bpf_attr {
  *     jump into another BPF program
  *     @ctx: context pointer passed to next program
  *     @prog_array_map: pointer to map which type is BPF_MAP_TYPE_PROG_ARRAY
- *     @index: index inside array that selects specific program to run
+ *     @index: 32-bit index inside array that selects specific program to run
  *     Return: 0 on success or negative error
  *
  * int bpf_clone_redirect(skb, ifindex, flags)

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 917cc04a0a94083d46f0a927e18f0228bf356c94..7b62df86be1d7e56044f947985b6c67ee5746c0d 100644 (file)
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -1022,7 +1022,7 @@ 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;