From: Martin KaFai Lau <kafai@fb.com>
Date: Tue, 22 May 2018 15:03:31 -0700
Subject: bpf: Expose check_uarg_tail_zero()
Patch-mainline: v4.18-rc1
Git-commit: dcab51f19b291d5ee23724c51b0a3a597c16451a
References: bsc#1109837

This patch exposes check_uarg_tail_zero() which will
be reused by a later BTF patch.  Its name is changed to
bpf_check_uarg_tail_zero().

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 include/linux/bpf.h  |    2 ++
 kernel/bpf/syscall.c |   14 +++++++-------
 2 files changed, 9 insertions(+), 7 deletions(-)

--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -434,6 +434,8 @@ int bpf_fd_htab_map_update_elem(struct b
 int bpf_fd_htab_map_lookup_elem(struct bpf_map *map, void *key, u32 *value);
 
 int bpf_get_file_flag(int flags);
+int bpf_check_uarg_tail_zero(void __user *uaddr, size_t expected_size,
+			     size_t actual_size);
 
 /* 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.
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -65,9 +65,9 @@ static const struct bpf_map_ops * const
  * copy_from_user() call. However, this is not a concern since this function is
  * meant to be a future-proofing of bits.
  */
-static int check_uarg_tail_zero(void __user *uaddr,
-				size_t expected_size,
-				size_t actual_size)
+int bpf_check_uarg_tail_zero(void __user *uaddr,
+			     size_t expected_size,
+			     size_t actual_size)
 {
 	unsigned char __user *addr;
 	unsigned char __user *end;
@@ -1727,7 +1727,7 @@ static int bpf_prog_get_info_by_fd(struc
 	u32 ulen;
 	int err;
 
-	err = check_uarg_tail_zero(uinfo, sizeof(info), info_len);
+	err = bpf_check_uarg_tail_zero(uinfo, sizeof(info), info_len);
 	if (err)
 		return err;
 	info_len = min_t(u32, sizeof(info), info_len);
@@ -1826,7 +1826,7 @@ static int bpf_map_get_info_by_fd(struct
 	u32 info_len = attr->info.info_len;
 	int err;
 
-	err = check_uarg_tail_zero(uinfo, sizeof(info), info_len);
+	err = bpf_check_uarg_tail_zero(uinfo, sizeof(info), info_len);
 	if (err)
 		return err;
 	info_len = min_t(u32, sizeof(info), info_len);
@@ -1866,7 +1866,7 @@ static int bpf_btf_get_info_by_fd(struct
 	u32 info_len = attr->info.info_len;
 	int err;
 
-	err = check_uarg_tail_zero(uinfo, sizeof(*uinfo), info_len);
+	err = bpf_check_uarg_tail_zero(uinfo, sizeof(*uinfo), info_len);
 	if (err)
 		return err;
 
@@ -1938,7 +1938,7 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf
 	if (sysctl_unprivileged_bpf_disabled && !capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
-	err = check_uarg_tail_zero(uattr, sizeof(attr), size);
+	err = bpf_check_uarg_tail_zero(uattr, sizeof(attr), size);
 	if (err)
 		return err;
 	size = min_t(u32, size, sizeof(attr));