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bpf: fix bpf_tail_call() x64 JIT
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- 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 96eabe7 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: 96eabe7 ("bpf: Allow selecting numa node during map creation")
Fixes: b52f00e ("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]>
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4ast authored and davem330 committed Oct 3, 2017
1 parent 0594687 commit 90caccd
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Showing 3 changed files with 4 additions and 4 deletions.
4 changes: 2 additions & 2 deletions arch/x86/net/bpf_jit_comp.c
Original file line number Diff line number Diff line change
Expand Up @@ -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;
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2 changes: 1 addition & 1 deletion include/uapi/linux/bpf.h
Original file line number Diff line number Diff line change
Expand Up @@ -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)
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2 changes: 1 addition & 1 deletion kernel/bpf/core.c
Original file line number Diff line number Diff line change
Expand Up @@ -1022,7 +1022,7 @@ static unsigned int ___bpf_prog_run(u64 *regs, const struct bpf_insn *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;
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