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bpf: Fix missing prog untrack in release_maps 

Commit da765a2f59 ("bpf: Add poke dependency tracking for prog array
maps") wrongly assumed that in case of prog load errors, we're cleaning
up all program tracking via bpf_free_used_maps().

However, it can happen that we're still at the point where we didn't copy
map pointers into the prog's aux section such that env->prog->aux->used_maps
is still zero, running into a UAF. In such case, the verifier has similar
release_maps() helper that drops references to used maps from its env.

Consolidate the release code into __bpf_free_used_maps() and call it from
all sides to fix it.

Fixes: da765a2f59 ("bpf: Add poke dependency tracking for prog array maps")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/1c2909484ca524ae9f55109b06f22b6213e76376.1576514756.git.daniel@iogearbox.net
alistair/sunxi64-5.5-dsi
Daniel Borkmann 2019-12-16 17:49:00 +01:00 committed by Alexei Starovoitov
parent 5133498f4a
commit a2ea07465c
3 changed files with 14 additions and 16 deletions
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2
include/linux/bpf.h
View File

@ -818,6 +818,8 @@ struct bpf_prog * __must_check bpf_prog_inc_not_zero(struct bpf_prog *prog);
void bpf_prog_put(struct bpf_prog *prog);
int __bpf_prog_charge(struct user_struct *user, u32 pages);
void __bpf_prog_uncharge(struct user_struct *user, u32 pages);
void __bpf_free_used_maps(struct bpf_prog_aux *aux,
struct bpf_map **used_maps, u32 len);
void bpf_prog_free_id(struct bpf_prog *prog, bool do_idr_lock);
void bpf_map_free_id(struct bpf_map *map, bool do_idr_lock);

14
kernel/bpf/core.c
View File

@ -2048,18 +2048,24 @@ static void bpf_free_cgroup_storage(struct bpf_prog_aux *aux)
}
}
static void bpf_free_used_maps(struct bpf_prog_aux *aux)
void __bpf_free_used_maps(struct bpf_prog_aux *aux,
struct bpf_map **used_maps, u32 len)
{
struct bpf_map *map;
int i;
u32 i;
bpf_free_cgroup_storage(aux);
for (i = 0; i < aux->used_map_cnt; i++) {
map = aux->used_maps[i];
for (i = 0; i < len; i++) {
map = used_maps[i];
if (map->ops->map_poke_untrack)
map->ops->map_poke_untrack(map, aux);
bpf_map_put(map);
}
}
static void bpf_free_used_maps(struct bpf_prog_aux *aux)
{
__bpf_free_used_maps(aux, aux->used_maps, aux->used_map_cnt);
kfree(aux->used_maps);
}

14
kernel/bpf/verifier.c
View File

@ -8298,18 +8298,8 @@ next_insn:
/* drop refcnt of maps used by the rejected program */
static void release_maps(struct bpf_verifier_env *env)
{
enum bpf_cgroup_storage_type stype;
int i;
for_each_cgroup_storage_type(stype) {
if (!env->prog->aux->cgroup_storage[stype])
continue;
bpf_cgroup_storage_release(env->prog,
env->prog->aux->cgroup_storage[stype]);
}
for (i = 0; i < env->used_map_cnt; i++)
bpf_map_put(env->used_maps[i]);
__bpf_free_used_maps(env->prog->aux, env->used_maps,
env->used_map_cnt);
}
/* convert pseudo BPF_LD_IMM64 into generic BPF_LD_IMM64 */