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Wei Liu
4b314c89be
Libxl ships output files from flex (libxlu_*_l.{c,h}). We use the flex
shipped in Debian to generate those files. Debian just patched their
flex (DSA 3653-1) to fix CVE-2016-6354, which is a buffer overrun bug.
Note that libxl is _NOT_ vulnerable to that CVE. See below for Ian's
analysis to security@xen.
It would still be nice that we update our shipped flex output files to
avoid confusion.
===QUOTE===
The bug is that with input >16K[1] flex would usually fail to resize
the input buffer, and then overrun it.
I have read the code in libxlu_cfg_l.c to try to understand the
implications for libxl.
AFAICT
- libxl always does config file reading _from the file_ itself, and
provides flex with a string or buffer.
- so we always call whatever_yy_scan_bytes, not any other flex setup
function to set up a `buffer' (as flex calls it)
- yy_scan_bytes calls yy_scan_buffer to set up the buffer
- yy_scan_buffer sets b->yy_fill_buffer
- The effect of this is that yy_get_next_buffer will always
return early, rather than continuing on to the vulnerable code.
So I think libxl is not vulnerable, regardless of the contents of the
configuration file.
[1] the default buffer size, or whatever other buffer size is
configured (but we don't change it)
===ENDQUOTE===
Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>