[PATCH bpf] bpf: fix integer overflow in queue_stack_map

[Alexei Starovoitov]

fix the following issues:
- allow queue_stack_map for root only
- fix u32 max_entries overflow
- disallow value_size == 0

Reported-by: Wei Wu <ww9...@gmail.com>
Fixes: f1a2e44a3aec ("bpf: add queue and stack maps")
Signed-off-by: Alexei Starovoitov <a...@kernel.org>
---
 kernel/bpf/queue_stack_maps.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/kernel/bpf/queue_stack_maps.c b/kernel/bpf/queue_stack_maps.c
index 8bbd72d3a121..b384ea9f3254 100644
--- a/kernel/bpf/queue_stack_maps.c
+++ b/kernel/bpf/queue_stack_maps.c
@@ -7,6 +7,7 @@
 #include <linux/bpf.h>
 #include <linux/list.h>
 #include <linux/slab.h>
+#include <linux/capability.h>
 #include "percpu_freelist.h"
 
 #define QUEUE_STACK_CREATE_FLAG_MASK \
@@ -45,8 +46,12 @@ static bool queue_stack_map_is_full(struct bpf_queue_stack 
*qs)
 /* Called from syscall */
 static int queue_stack_map_alloc_check(union bpf_attr *attr)
 {
+       if (!capable(CAP_SYS_ADMIN))
+               return -EPERM;
+
        /* check sanity of attributes */
        if (attr->max_entries == 0 || attr->key_size != 0 ||
+           attr->value_size == 0 ||
            attr->map_flags & ~QUEUE_STACK_CREATE_FLAG_MASK)
                return -EINVAL;
 
@@ -63,15 +68,10 @@ static struct bpf_map *queue_stack_map_alloc(union bpf_attr 
*attr)
 {
        int ret, numa_node = bpf_map_attr_numa_node(attr);
        struct bpf_queue_stack *qs;
-       u32 size, value_size;
-       u64 queue_size, cost;
-
-       size = attr->max_entries + 1;
-       value_size = attr->value_size;
-
-       queue_size = sizeof(*qs) + (u64) value_size * size;
+       u64 size, queue_size, cost;
 
-       cost = queue_size;
+       size = (u64) attr->max_entries + 1;
+       cost = queue_size = sizeof(*qs) + size * attr->value_size;
        if (cost >= U32_MAX - PAGE_SIZE)
                return ERR_PTR(-E2BIG);
 
-- 
2.17.1