bpf: perf_event progs should only use preallocated maps

Make sure that BPF_PROG_TYPE_PERF_EVENT programs only use
preallocated hash maps, since doing memory allocation
in overflow_handler can crash depending on where nmi got triggered.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 21 insertions, 1 deletions

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index c1c9e441f0f5..48c2705db22c 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2511,6 +2511,20 @@ process_bpf_exit:
         return 0;
 }
 
+static int check_map_prog_compatibility(struct bpf_map *map,
+                                        struct bpf_prog *prog)
+
+{
+        if (prog->type == BPF_PROG_TYPE_PERF_EVENT &&
+            (map->map_type == BPF_MAP_TYPE_HASH ||
+             map->map_type == BPF_MAP_TYPE_PERCPU_HASH) &&
+            (map->map_flags & BPF_F_NO_PREALLOC)) {
+                verbose("perf_event programs can only use preallocated hash map\n");
+                return -EINVAL;
+        }
+        return 0;
+}
+
 /* look for pseudo eBPF instructions that access map FDs and
  * replace them with actual map pointers
  */
@@ -2518,7 +2532,7 @@ static int replace_map_fd_with_map_ptr(struct verifier_env *env)
 {
         struct bpf_insn *insn = env->prog->insnsi;
         int insn_cnt = env->prog->len;
-        int i, j;
+        int i, j, err;
 
         for (i = 0; i < insn_cnt; i++, insn++) {
                 if (BPF_CLASS(insn->code) == BPF_LDX &&
@@ -2562,6 +2576,12 @@ static int replace_map_fd_with_map_ptr(struct verifier_env *env)
                                 return PTR_ERR(map);
                         }
 
+                        err = check_map_prog_compatibility(map, env->prog);
+                        if (err) {
+                                fdput(f);
+                                return err;
+                        }
+
                         /* store map pointer inside BPF_LD_IMM64 instruction */
                         insn[0].imm = (u32) (unsigned long) map;
                         insn[1].imm = ((u64) (unsigned long) map) >> 32;