[PATCH 9/9] bpf: make bpf_check_uarg_tail_zero() use check_zeroed_user()

[Al Viro]

From: Al Viro <v...@zeniv.linux.org.uk>

... rather than open-coding it, and badly, at that.

Signed-off-by: Al Viro <v...@zeniv.linux.org.uk>
---
 kernel/bpf/syscall.c | 25 ++++++-------------------
 1 file changed, 6 insertions(+), 19 deletions(-)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 64783da34202..41ba746ecbc2 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -67,32 +67,19 @@ 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;
-       unsigned char val;
-       int err;
+       unsigned char __user *addr = uaddr + expected_size;
+       int res;
 
        if (unlikely(actual_size > PAGE_SIZE))  /* silly large */
                return -E2BIG;
 
-       if (unlikely(!access_ok(uaddr, actual_size)))
-               return -EFAULT;
-
        if (actual_size <= expected_size)
                return 0;
 
-       addr = uaddr + expected_size;
-       end  = uaddr + actual_size;
-
-       for (; addr < end; addr++) {
-               err = get_user(val, addr);
-               if (err)
-                       return err;
-               if (val)
-                       return -E2BIG;
-       }
-
-       return 0;
+       res = check_zeroed_user(addr, actual_size - expected_size);
+       if (res < 0)
+               return res;
+       return res ? 0 : -E2BIG;
 }
 
 const struct bpf_map_ops bpf_map_offload_ops = {
-- 
2.11.0