[ upstream commit 9c2d63b843a5c8a8d0559cc067b5398aa5ec3ffc ]
syzkaller recently triggered OOM during percpu map allocation; while there is work in progress by Dennis Zhou to add __GFP_NORETRY semantics for percpu allocator under pressure, there seems also a missing bpf_map_precharge_memlock() check in array map allocation.
Given today the actual bpf_map_charge_memlock() happens after the find_and_alloc_map() in syscall path, the bpf_map_precharge_memlock() is there to bail out early before we go and do the map setup work when we find that we hit the limits anyway. Therefore add this for array map as well.
Fixes: 6c9059817432 ("bpf: pre-allocate hash map elements") Fixes: a10423b87a7e ("bpf: introduce BPF_MAP_TYPE_PERCPU_ARRAY map") Reported-by: syzbot+adb03f3f0bb57ce3acda@syzkaller.appspotmail.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Cc: Dennis Zhou dennisszhou@gmail.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Daniel Borkmann daniel@iogearbox.net --- kernel/bpf/arraymap.c | 29 ++++++++++++++++++----------- 1 file changed, 18 insertions(+), 11 deletions(-)
diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c index 3be357a..075ddb8 100644 --- a/kernel/bpf/arraymap.c +++ b/kernel/bpf/arraymap.c @@ -48,8 +48,9 @@ static struct bpf_map *array_map_alloc(union bpf_attr *attr) bool percpu = attr->map_type == BPF_MAP_TYPE_PERCPU_ARRAY; u32 elem_size, index_mask, max_entries; bool unpriv = !capable(CAP_SYS_ADMIN); + u64 cost, array_size, mask64; struct bpf_array *array; - u64 array_size, mask64; + int ret;
/* check sanity of attributes */ if (attr->max_entries == 0 || attr->key_size != 4 || @@ -92,8 +93,19 @@ static struct bpf_map *array_map_alloc(union bpf_attr *attr) array_size += (u64) max_entries * elem_size;
/* make sure there is no u32 overflow later in round_up() */ - if (array_size >= U32_MAX - PAGE_SIZE) + cost = array_size; + if (cost >= U32_MAX - PAGE_SIZE) return ERR_PTR(-ENOMEM); + if (percpu) { + cost += (u64)attr->max_entries * elem_size * num_possible_cpus(); + if (cost >= U32_MAX - PAGE_SIZE) + return ERR_PTR(-ENOMEM); + } + cost = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT; + + ret = bpf_map_precharge_memlock(cost); + if (ret < 0) + return ERR_PTR(ret);
/* allocate all map elements and zero-initialize them */ array = bpf_map_area_alloc(array_size); @@ -108,20 +120,15 @@ static struct bpf_map *array_map_alloc(union bpf_attr *attr) array->map.value_size = attr->value_size; array->map.max_entries = attr->max_entries; array->map.map_flags = attr->map_flags; + array->map.pages = cost; array->elem_size = elem_size;
- if (!percpu) - goto out; - - array_size += (u64) attr->max_entries * elem_size * num_possible_cpus(); - - if (array_size >= U32_MAX - PAGE_SIZE || - elem_size > PCPU_MIN_UNIT_SIZE || bpf_array_alloc_percpu(array)) { + if (percpu && + (elem_size > PCPU_MIN_UNIT_SIZE || + bpf_array_alloc_percpu(array))) { bpf_map_area_free(array); return ERR_PTR(-ENOMEM); } -out: - array->map.pages = round_up(array_size, PAGE_SIZE) >> PAGE_SHIFT;
return &array->map; }