- 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 <fengguang...@intel.com>
Signed-off-by: Alexei Starovoitov <a...@plumgrid.com>
---
This silly NULL deref bug and missing overflow check was an oversight when
I refactored the code from two allocations (kmalloc for struct bpf_array and
kcalloc for array of elements) in the first implementation of arraymap
into one allocation which is this code.
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);
--
1.7.9.5
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