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bpf: perf_event progs should only use preallocated maps

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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>
This commit is contained in:
Alexei Starovoitov 2016-09-01 18:37:23 -07:00 committed by David S. Miller
parent 0515e5999a
commit fdc15d388d
1 changed files with 21 additions and 1 deletions
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22
kernel/bpf/verifier.c
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@ -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;