fs: sysfs: return EGBIG on write if offset is larger than file size

According to the user expectations common utilities like dd or sh
redirection operator > should work correctly over binary files from
sysfs. At the moment doing excessive write can not be completed:

  write(1, "\0\0\0\0\0\0\0\0", 8)         = 4
  write(1, "\0\0\0\0", 4)                 = 0
  write(1, "\0\0\0\0", 4)                 = 0
  write(1, "\0\0\0\0", 4)                 = 0
  ...

Fix the problem by returning EFBIG described in man 2 write.

Signed-off-by: Vladimir Zapolskiy <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

fs/sysfs/file.c

@@ -125,7 +125,7 @@ static ssize_t sysfs_kf_bin_write(struct kernfs_open_file *of, char *buf,
 
 	if (size) {
 		if (size <= pos)
-			return 0;
+			return -EFBIG;
 		count = min_t(ssize_t, count, size - pos);
 	}
 	if (!count)