From: Chenbo Feng <fengc@xxxxxxxxxx>
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.
Signed-off-by: Chenbo Feng <fengc@xxxxxxxxxx>
Acked-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Acked-by: Alexei Starovoitov <ast@xxxxxxxxxx>
---
include/linux/bpf.h | 6 ++--
include/uapi/linux/bpf.h | 6 ++++
kernel/bpf/inode.c | 15 ++++++---
kernel/bpf/syscall.c | 80 +++++++++++++++++++++++++++++++++++++++++++-----
4 files changed, 92 insertions(+), 15 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 252f4bc9eb25..d826be859589 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -273,11 +273,11 @@ void bpf_map_area_free(void *base);
extern int sysctl_unprivileged_bpf_disabled;
-int bpf_map_new_fd(struct bpf_map *map);
+int bpf_map_new_fd(struct bpf_map *map, int flags);
int bpf_prog_new_fd(struct bpf_prog *prog);
int bpf_obj_pin_user(u32 ufd, const char __user *pathname);
-int bpf_obj_get_user(const char __user *pathname);
+int bpf_obj_get_user(const char __user *pathname, int flags);
int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value);
int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value);
@@ -296,6 +296,8 @@ int bpf_fd_htab_map_update_elem(struct bpf_map *map, struct file *map_file,
void *key, void *value, u64 map_flags);
int bpf_fd_htab_map_lookup_elem(struct bpf_map *map, void *key, u32 *value);
+int bpf_get_file_flag(int flags);
+
/* memcpy that is used with 8-byte aligned pointers, power-of-8 size and
* forced to use 'long' read/writes to try to atomically copy long counters.
* Best-effort only. No barriers here, since it _will_ race with concurrent
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 6d2137b4cf38..e812be5946a6 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -177,6 +177,10 @@ enum bpf_attach_type {
#define BPF_OBJ_NAME_LEN 16U
+/* Flags for accessing BPF object */
+#define BPF_F_RDONLY (1U << 3)
+#define BPF_F_WRONLY (1U << 4)
+
union bpf_attr {
struct { /* anonymous struct used by BPF_MAP_CREATE command */
__u32 map_type; /* one of enum bpf_map_type */
@@ -219,6 +223,7 @@ union bpf_attr {
struct { /* anonymous struct used by BPF_OBJ_* commands */
__aligned_u64 pathname;
__u32 bpf_fd;
+ __u32 file_flags;
};
struct { /* anonymous struct used by BPF_PROG_ATTACH/DETACH commands */
@@ -246,6 +251,7 @@ union bpf_attr {
__u32 map_id;
};
__u32 next_id;
+ __u32 open_flags;
};
struct { /* anonymous struct used by BPF_OBJ_GET_INFO_BY_FD */
diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c
index e833ed914358..7d8c6dd8dd5d 100644
--- a/kernel/bpf/inode.c
+++ b/kernel/bpf/inode.c
@@ -295,7 +295,7 @@ int bpf_obj_pin_user(u32 ufd, const char __user *pathname)
}
static void *bpf_obj_do_get(const struct filename *pathname,
- enum bpf_type *type)
+ enum bpf_type *type, int flags)
{
struct inode *inode;
struct path path;
@@ -307,7 +307,7 @@ static void *bpf_obj_do_get(const struct filename *pathname,
return ERR_PTR(ret);
inode = d_backing_inode(path.dentry);
- ret = inode_permission(inode, MAY_WRITE);
+ ret = inode_permission(inode, ACC_MODE(flags));
if (ret)
goto out;
@@ -326,18 +326,23 @@ static void *bpf_obj_do_get(const struct filename *pathname,
return ERR_PTR(ret);
}
-int bpf_obj_get_user(const char __user *pathname)
+int bpf_obj_get_user(const char __user *pathname, int flags)
{
enum bpf_type type = BPF_TYPE_UNSPEC;
struct filename *pname;
int ret = -ENOENT;
+ int f_flags;
void *raw;
+ f_flags = bpf_get_file_flag(flags);
+ if (f_flags < 0)
+ return f_flags;
+
pname = getname(pathname);
if (IS_ERR(pname))
return PTR_ERR(pname);
- raw = bpf_obj_do_get(pname, &type);
+ raw = bpf_obj_do_get(pname, &type, f_flags);
if (IS_ERR(raw)) {
ret = PTR_ERR(raw);
goto out;
@@ -346,7 +351,7 @@ int bpf_obj_get_user(const char __user *pathname)
if (type == BPF_TYPE_PROG)
ret = bpf_prog_new_fd(raw);
else if (type == BPF_TYPE_MAP)
- ret = bpf_map_new_fd(raw);
+ ret = bpf_map_new_fd(raw, f_flags);
else
goto out;
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index b927da66f653..7c8a9964a41d 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -294,17 +294,48 @@ static void bpf_map_show_fdinfo(struct seq_file *m, struct file *filp)
}
#endif
+static ssize_t bpf_dummy_read(struct file *filp, char __user *buf, size_t siz,
+ loff_t *ppos)
+{
+ /* We need this handler such that alloc_file() enables
+ * f_mode with FMODE_CAN_READ.
+ */
+ return -EINVAL;
+}
+
+static ssize_t bpf_dummy_write(struct file *filp, const char __user *buf,
+ size_t siz, loff_t *ppos)
+{
+ /* We need this handler such that alloc_file() enables
+ * f_mode with FMODE_CAN_WRITE.
+ */
+ return -EINVAL;
+}
+
static const struct file_operations bpf_map_fops = {
#ifdef CONFIG_PROC_FS
.show_fdinfo = bpf_map_show_fdinfo,
#endif
.release = bpf_map_release,
+ .read = bpf_dummy_read,
+ .write = bpf_dummy_write,
};
-int bpf_map_new_fd(struct bpf_map *map)
+int bpf_map_new_fd(struct bpf_map *map, int flags)
{
return anon_inode_getfd("bpf-map", &bpf_map_fops, map,
- O_RDWR | O_CLOEXEC);
+ flags | O_CLOEXEC);
+}
+
+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;
+
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)
if (IS_ERR(map))
return PTR_ERR(map);
+ if (!(f.file->f_mode & FMODE_CAN_READ)) {
+ err = -EPERM;
+ goto err_put;
+ }
+
key = memdup_user(ukey, map->key_size);
if (IS_ERR(key)) {
err = PTR_ERR(key);
@@ -571,6 +612,11 @@ static int map_update_elem(union bpf_attr *attr)
if (IS_ERR(map))
return PTR_ERR(map);
+ if (!(f.file->f_mode & FMODE_CAN_WRITE)) {
+ err = -EPERM;
+ goto err_put;
+ }
+
key = memdup_user(ukey, map->key_size);
if (IS_ERR(key)) {
err = PTR_ERR(key);
@@ -654,6 +700,11 @@ static int map_delete_elem(union bpf_attr *attr)
if (IS_ERR(map))
return PTR_ERR(map);
+ if (!(f.file->f_mode & FMODE_CAN_WRITE)) {
+ err = -EPERM;
+ goto err_put;
+ }
+
key = memdup_user(ukey, map->key_size);
if (IS_ERR(key)) {
err = PTR_ERR(key);
@@ -697,6 +748,11 @@ static int map_get_next_key(union bpf_attr *attr)
if (IS_ERR(map))
return PTR_ERR(map);
+ if (!(f.file->f_mode & FMODE_CAN_READ)) {
+ err = -EPERM;
+ goto err_put;
+ }
+
if (ukey) {
key = memdup_user(ukey, map->key_size);
if (IS_ERR(key)) {
@@ -903,6 +959,8 @@ static const struct file_operations bpf_prog_fops = {
.show_fdinfo = bpf_prog_show_fdinfo,
#endif
.release = bpf_prog_release,
+ .read = bpf_dummy_read,
+ .write = bpf_dummy_write,
};
int bpf_prog_new_fd(struct bpf_prog *prog)
@@ -1112,11 +1170,11 @@ static int bpf_prog_load(union bpf_attr *attr)
return err;
}
-#define BPF_OBJ_LAST_FIELD bpf_fd
+#define BPF_OBJ_LAST_FIELD file_flags
static int bpf_obj_pin(const union bpf_attr *attr)
{
- if (CHECK_ATTR(BPF_OBJ))
+ if (CHECK_ATTR(BPF_OBJ) || attr->file_flags != 0)
return -EINVAL;
return bpf_obj_pin_user(attr->bpf_fd, u64_to_user_ptr(attr->pathname));
@@ -1127,7 +1185,8 @@ static int bpf_obj_get(const union bpf_attr *attr)
if (CHECK_ATTR(BPF_OBJ) || attr->bpf_fd != 0)
return -EINVAL;
- return bpf_obj_get_user(u64_to_user_ptr(attr->pathname));
+ return bpf_obj_get_user(u64_to_user_ptr(attr->pathname),
+ attr->file_flags);
}
#ifdef CONFIG_CGROUP_BPF
@@ -1341,12 +1400,13 @@ static int bpf_prog_get_fd_by_id(const union bpf_attr *attr)
return fd;
}
-#define BPF_MAP_GET_FD_BY_ID_LAST_FIELD map_id
+#define BPF_MAP_GET_FD_BY_ID_LAST_FIELD open_flags
static int bpf_map_get_fd_by_id(const union bpf_attr *attr)
{
struct bpf_map *map;
u32 id = attr->map_id;
+ int f_flags;
int fd;
if (CHECK_ATTR(BPF_MAP_GET_FD_BY_ID))
@@ -1355,6 +1415,10 @@ static int bpf_map_get_fd_by_id(const union bpf_attr *attr)
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
+ f_flags = bpf_get_file_flag(attr->open_flags);
+ if (f_flags < 0)
+ return f_flags;
+
spin_lock_bh(&map_idr_lock);
map = idr_find(&map_idr, id);
if (map)
@@ -1366,7 +1430,7 @@ static int bpf_map_get_fd_by_id(const union bpf_attr *attr)
if (IS_ERR(map))
return PTR_ERR(map);
- fd = bpf_map_new_fd(map);
+ fd = bpf_map_new_fd(map, f_flags);
if (fd < 0)
bpf_map_put(map);
--
2.14.2.920.gcf0c67979c-goog
