BACKPORT: bpf: Add file mode configuration into bpf maps

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@google.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

Deleted the file mode configuration code in unsupported map type and
removed the file mode check in non-existing helper functions.
(cherry-pick from net-next: 6e71b04a82248ccf13a94b85cbc674a9fefe53f5)
Bug: 30950746

Change-Id: Icfad20f1abb77f91068d244fb0d87fa40824dd1b
Signed-off-by: Chatur27 <jasonbright2709@gmail.com>

1 files changed, 10 insertions, 5 deletions

diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c
index 5967b870a895..cf9a4e7213a0 100644
--- a/kernel/bpf/inode.c
+++ b/kernel/bpf/inode.c
@@ -255,7 +255,7 @@ out:
 }
 
 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;
@@ -267,7 +267,7 @@ 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;
 
@@ -286,18 +286,23 @@ out:
 	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;
@@ -306,7 +311,7 @@ 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;