BACKPORT: fix "netfilter: xt_bpf: Fix XT_BPF_MODE_FD_PINNED mode of 'xt_bpf_info_v1'"

Descriptor table is a shared object; it's not a place where you can
stick temporary references to files, especially when we don't need
an opened file at all.

Cc: stable@vger.kernel.org # v4.14
Fixes: 98589a0998b8 ("netfilter: xt_bpf: Fix XT_BPF_MODE_FD_PINNED mode of 'xt_bpf_info_v1'")
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Chenbo Feng <fengc@google.com>

Removed the code related to function bpf_prog_get_ok() since it is not
exsit in current android tree.
(cherry picked from commit 040ee69226f8a96b7943645d68f41d5d44b5ff7d)

Change-Id: If7a602128cdea4b4b50c8effb215c9bca7449515
Signed-off-by: Chatur27 <jasonbright2709@gmail.com>

3 files changed, 46 insertions, 12 deletions

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 8ea952e7d8e5..57c30ae87ddf 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -297,6 +297,9 @@ static inline void bpf_long_memcpy(void *dst, const void *src, u32 size)
 
 /* verify correctness of eBPF program */
 int bpf_check(struct bpf_prog **fp, union bpf_attr *attr);
+
+struct bpf_prog *bpf_prog_get_type_path(const char *name, enum bpf_prog_type type);
+
 #else
 static inline void bpf_register_prog_type(struct bpf_prog_type_list *tl)
 {
@@ -325,6 +328,11 @@ static inline int bpf_obj_get_user(const char __user *pathname)
 	return -EOPNOTSUPP;
 }
 
+static inline struct bpf_prog *bpf_prog_get_type_path(const char *name,
+				enum bpf_prog_type type)
+{
+	return ERR_PTR(-EOPNOTSUPP);
+}
 #endif /* CONFIG_BPF_SYSCALL */
 
 /* verifier prototypes for helper functions called from eBPF programs */
diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c
index 744a451feafe..56f3ab785c68 100644
--- a/kernel/bpf/inode.c
+++ b/kernel/bpf/inode.c
@@ -321,7 +321,42 @@ out:
 	putname(pname);
 	return ret;
 }
-EXPORT_SYMBOL_GPL(bpf_obj_get_user);
+
+static struct bpf_prog *__get_prog_inode(struct inode *inode, enum bpf_prog_type type)
+{
+	struct bpf_prog *prog;
+	int ret = inode_permission(inode, MAY_READ | MAY_WRITE);
+	if (ret)
+		return ERR_PTR(ret);
+
+	if (inode->i_op == &bpf_map_iops)
+		return ERR_PTR(-EINVAL);
+	if (inode->i_op != &bpf_prog_iops)
+		return ERR_PTR(-EACCES);
+
+	prog = inode->i_private;
+
+	ret = security_bpf_prog(prog);
+	if (ret < 0)
+		return ERR_PTR(ret);
+
+	return bpf_prog_inc(prog);
+}
+
+struct bpf_prog *bpf_prog_get_type_path(const char *name, enum bpf_prog_type type)
+{
+	struct bpf_prog *prog;
+	struct path path;
+	int ret = kern_path(name, LOOKUP_FOLLOW, &path);
+	if (ret)
+		return ERR_PTR(ret);
+	prog = __get_prog_inode(d_backing_inode(path.dentry), type);
+	if (!IS_ERR(prog))
+		touch_atime(&path);
+	path_put(&path);
+	return prog;
+}
+EXPORT_SYMBOL(bpf_prog_get_type_path);
 
 static void bpf_evict_inode(struct inode *inode)
 {
diff --git a/net/netfilter/xt_bpf.c b/net/netfilter/xt_bpf.c
index 5185ff0f8f58..7e7746cc45d6 100644
--- a/net/netfilter/xt_bpf.c
+++ b/net/netfilter/xt_bpf.c
@@ -55,21 +55,12 @@ static int __bpf_mt_check_fd(int fd, struct bpf_prog **ret)
 
 static int __bpf_mt_check_path(const char *path, struct bpf_prog **ret)
 {
-	mm_segment_t oldfs = get_fs();
-	int retval, fd;
-
 	if (strnlen(path, XT_BPF_PATH_MAX) == XT_BPF_PATH_MAX)
 		return -EINVAL;
 
-	set_fs(KERNEL_DS);
-	fd = bpf_obj_get_user(path);
-	set_fs(oldfs);
-	if (fd < 0)
-		return fd;
+	*ret = bpf_prog_get_type_path(path, BPF_PROG_TYPE_SOCKET_FILTER);
+	return PTR_ERR_OR_ZERO(*ret);
 
-	retval = __bpf_mt_check_fd(fd, ret);
-	sys_close(fd);
-	return retval;
 }
 
 static int bpf_mt_check(const struct xt_mtchk_param *par)