From daaf427c6ab392bedcd018e326b2ffa1e1110cd6 Mon Sep 17 00:00:00 2001 From: Alexei Starovoitov Date: Tue, 18 Nov 2014 17:32:16 -0800 Subject: [PATCH] bpf: fix arraymap NULL deref and missing overflow and zero size checks - fix NULL pointer dereference: kernel/bpf/arraymap.c:41 array_map_alloc() error: potential null dereference 'array'. (kzalloc returns null) kernel/bpf/arraymap.c:41 array_map_alloc() error: we previously assumed 'array' could be null (see line 40) - integer overflow check was missing in arraymap (hashmap checks for overflow via kmalloc_array()) - arraymap can round_up(value_size, 8) to zero. check was missing. - hashmap was missing zero size check as well, since roundup_pow_of_two() can truncate into zero - found a typo in the arraymap comment and unnecessary empty line Fix all of these issues and make both overflow checks explicit U32 in size. Reported-by: kbuild test robot Signed-off-by: Alexei Starovoitov Signed-off-by: David S. Miller --- kernel/bpf/arraymap.c | 17 +++++++++++------ kernel/bpf/hashtab.c | 5 +++++ 2 files changed, 16 insertions(+), 6 deletions(-) diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c index 58b80c137afd..9eb4d8a7cd87 100644 --- a/kernel/bpf/arraymap.c +++ b/kernel/bpf/arraymap.c @@ -25,7 +25,7 @@ struct bpf_array { static struct bpf_map *array_map_alloc(union bpf_attr *attr) { struct bpf_array *array; - u32 elem_size; + u32 elem_size, array_size; /* check sanity of attributes */ if (attr->max_entries == 0 || attr->key_size != 4 || @@ -34,11 +34,17 @@ static struct bpf_map *array_map_alloc(union bpf_attr *attr) elem_size = round_up(attr->value_size, 8); + /* check round_up into zero and u32 overflow */ + if (elem_size == 0 || + attr->max_entries > (U32_MAX - sizeof(*array)) / elem_size) + return ERR_PTR(-ENOMEM); + + array_size = sizeof(*array) + attr->max_entries * elem_size; + /* allocate all map elements and zero-initialize them */ - array = kzalloc(sizeof(*array) + attr->max_entries * elem_size, - GFP_USER | __GFP_NOWARN); + array = kzalloc(array_size, GFP_USER | __GFP_NOWARN); if (!array) { - array = vzalloc(array->map.max_entries * array->elem_size); + array = vzalloc(array_size); if (!array) return ERR_PTR(-ENOMEM); } @@ -51,7 +57,6 @@ static struct bpf_map *array_map_alloc(union bpf_attr *attr) array->elem_size = elem_size; return &array->map; - } /* Called from syscall or from eBPF program */ @@ -101,7 +106,7 @@ static int array_map_update_elem(struct bpf_map *map, void *key, void *value, return -E2BIG; if (map_flags == BPF_NOEXIST) - /* all elemenets already exist */ + /* all elements already exist */ return -EEXIST; memcpy(array->value + array->elem_size * index, value, array->elem_size); diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c index d234a012f046..b3ba43674310 100644 --- a/kernel/bpf/hashtab.c +++ b/kernel/bpf/hashtab.c @@ -65,6 +65,11 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr) goto free_htab; err = -ENOMEM; + /* prevent zero size kmalloc and check for u32 overflow */ + if (htab->n_buckets == 0 || + htab->n_buckets > U32_MAX / sizeof(struct hlist_head)) + goto free_htab; + htab->buckets = kmalloc_array(htab->n_buckets, sizeof(struct hlist_head), GFP_USER | __GFP_NOWARN); -- 2.20.1