Created attachment 417508 [details]
guestfish write-file cmd logs

Description of problem:
guestfish write-file cmd does not check the size parameter, this cause two issues:
1. if size is greater than the actual string length, random content will returned and written to the file, I guess it just overflow the char* pointer address and dump the XDR buffer to file
2. if size is negative or a great value that exceeds XDR buffer,will cause "bad address" error

Version-Release number of selected component (if applicable):


How reproducible:
100%

Steps to Reproduce:
1. run guestfish with an existing image
2. issue cmd " write-file /t.txt  "abcdefg" SIZE
3. SIZE could be some vaule great than the string leng, such as 10000
  
Actual results:
random content will return with size larger than actual string length

Expected results:
Should not return random content nor "bad address" error, size should be checked in do_write_file function

Additional info:
logs appended