On 10/04/2017 08:29 PM, Chenbo Feng wrote:
From: Chenbo Feng <fe...@google.com>
Introduce the map read/write flags to the eBPF syscalls that returns the
map fd. The flags is used to set up the file mode when construct a new
file descriptor for bpf maps. To not break the backward capability, the
f_flags is set to O_RDWR if the flag passed by syscall is 0. Otherwise
it should be O_RDONLY or O_WRONLY. When the userspace want to modify or
read the map content, it will check the file mode to see if it is
allowed to make the change.
[...]
+int bpf_get_file_flag(int flags)
+{
+ if ((flags & BPF_F_RDONLY) && (flags & BPF_F_WRONLY))
+ return -EINVAL;
+ if (flags & BPF_F_RDONLY)
+ return O_RDONLY;
+ if (flags & BPF_F_WRONLY)
+ return O_WRONLY;
+ return O_RDWR;
}
/* helper macro to check that unused fields 'union bpf_attr' are zero */
@@ -345,12 +376,17 @@ static int map_create(union bpf_attr *attr)
{
int numa_node = bpf_map_attr_numa_node(attr);
struct bpf_map *map;
+ int f_flags;
int err;
err = CHECK_ATTR(BPF_MAP_CREATE);
if (err)
return -EINVAL;
+ f_flags = bpf_get_file_flag(attr->map_flags);
+ if (f_flags < 0)
+ return f_flags;
Wait, I just noticed, given you add BPF_F_RDONLY/BPF_F_WRONLY
to attr->map_flags, and later go into find_and_alloc_map(),
for map alloc, which is e.g. array_map_alloc(). There, we
bail out with EINVAL on attr->map_flags & ~BPF_F_NUMA_NODE,
which is the case for both BPF_F_RDONLY/BPF_F_WRONLY ... I
would have expected that the entire code was tested properly;
what was tested exactly in the set?
if (numa_node != NUMA_NO_NODE &&
((unsigned int)numa_node >= nr_node_ids ||
!node_online(numa_node)))
@@ -376,7 +412,7 @@ static int map_create(union bpf_attr *attr)
if (err)
goto free_map;
- err = bpf_map_new_fd(map);
+ err = bpf_map_new_fd(map, f_flags);
if (err < 0) {
/* failed to allocate fd.
* bpf_map_put() is needed because the above
@@ -491,6 +527,11 @@ static int map_lookup_elem(union bpf_attr *attr)
[...]
