Re: [Lzip-bug] silent data corruption by lzip-1.2-pre1

[Antonio Diaz Diaz]

John Reiser wrote:
> Here is an example of lzip-1.2-pre1 corrupting data silently.
>
> $ ./lzip -s30 foo   # compress

Thank you for finding this bug. The maximum safe value for -s is 29, not 
30. I didn't find it myself because a machine with more than 6GiB of RAM 
is needed to test -s30 (mine has only 512MiB). Please test the following 
patch:

----------------------------------------------------
diff -urdN ../old_src/lzip.h ./lzip.h
--- ../old_src/lzip.h   2008-11-20 19:48:21.000000000 +0100
+++ ./lzip.h    2008-12-05 15:48:58.000000000 +0100
@@ -49,7 +49,7 @@


 const int min_dictionary_bits = 12;
-const int max_dictionary_bits = 30;
+const int max_dictionary_bits = 29;
 const int literal_context_bits = 3;
 const int pos_state_bits = 2;
 const int pos_states = 1 << pos_state_bits;
----------------------------------------------------


>    User documentation "./lzip --help" is incorrect for "-s".

It is incomplete because "lzip --help" is intended as a fast reminder of 
lzip usage. For a more complete info you can read the fine manual:

`--dictionary-size=SIZE'
`-s SIZE'
     Set the dictionary size in bytes. Dictionary size is always a
     power of two. You may specify it as the number of bits to use or
     as a size between 4KiB and 1GiB. If the specified size is not a
     power of two, it is rounded upwards.


A corrected version will be released shortly.


Best regards,
Antonio.