From: Al Viro <viro@zeniv.linux.org.uk>
Date: Sat, 2 Dec 2017 20:20:38 -0500
Subject: fix "netfilter: xt_bpf: Fix XT_BPF_MODE_FD_PINNED mode of
 'xt_bpf_info_v1'"
Patch-mainline: v4.15-rc7
Git-commit: 040ee69226f8a96b7943645d68f41d5d44b5ff7d
References: bsc#1109837

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>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 include/linux/bpf.h    |   10 ++++++++++
 kernel/bpf/inode.c     |   36 +++++++++++++++++++++++++++++++++++-
 kernel/bpf/syscall.c   |    2 +-
 net/netfilter/xt_bpf.c |   17 ++---------------
 4 files changed, 48 insertions(+), 17 deletions(-)

--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -390,6 +390,8 @@ static inline int bpf_map_attr_numa_node
 		attr->numa_node : NUMA_NO_NODE;
 }
 
+struct bpf_prog *bpf_prog_get_type_path(const char *name, enum bpf_prog_type type);
+
 #else /* !CONFIG_BPF_SYSCALL */
 static inline struct bpf_prog *bpf_prog_get(u32 ufd)
 {
@@ -477,6 +479,12 @@ static inline int cpu_map_enqueue(struct
 {
 	return 0;
 }
+
+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 */
 
 static inline struct bpf_prog *bpf_prog_get_type(u32 ufd,
@@ -485,6 +493,8 @@ static inline struct bpf_prog *bpf_prog_
 	return bpf_prog_get_type_dev(ufd, type, false);
 }
 
+bool bpf_prog_get_ok(struct bpf_prog *, enum bpf_prog_type *, bool);
+
 int bpf_prog_offload_compile(struct bpf_prog *prog);
 void bpf_prog_offload_destroy(struct bpf_prog *prog);
 
--- a/kernel/bpf/inode.c
+++ b/kernel/bpf/inode.c
@@ -368,7 +368,41 @@ 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;
+
+	if (!bpf_prog_get_ok(prog, &type, false))
+		return ERR_PTR(-EINVAL);
+
+	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)
 {
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1037,7 +1037,7 @@ struct bpf_prog *bpf_prog_inc_not_zero(s
 }
 EXPORT_SYMBOL_GPL(bpf_prog_inc_not_zero);
 
-static bool bpf_prog_get_ok(struct bpf_prog *prog,
+bool bpf_prog_get_ok(struct bpf_prog *prog,
 			    enum bpf_prog_type *attach_type, bool attach_drv)
 {
 	/* not an attachment, just a refcount inc, always allow */
--- a/net/netfilter/xt_bpf.c
+++ b/net/netfilter/xt_bpf.c
@@ -55,21 +55,8 @@ static int __bpf_mt_check_fd(int fd, str
 
 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, 0);
-	set_fs(oldfs);
-	if (fd < 0)
-		return fd;
-
-	retval = __bpf_mt_check_fd(fd, ret);
-	sys_close(fd);
-	return retval;
+	*ret = bpf_prog_get_type_path(path, BPF_PROG_TYPE_SOCKET_FILTER);
+	return PTR_ERR_OR_ZERO(*ret);
 }
 
 static int bpf_mt_check(const struct xt_mtchk_param *par)