less: fix CVE-2014-9488

less: fix CVE-2014-9488

An out of bounds read access in the UTF-8 decoding can be triggered with
a malformed file in the tool less. The access happens in the function
is_utf8_well_formed due to a truncated multibyte character in the sample
file.

The bug does not crash less, it can only be made visible by running less
with valgrind or compiling it with Address Sanitizer.

Version 475 of less contains a fix for this issue. The file version.c
contains some entry mentioning this issue (without any credit):

 - v475 3/2/15 Fix possible buffer overrun with invalid UTF-8

The fix is in the file line.c. We derive this patch from:

https://blog.fuzzing-project.org/3-less-out-of-bounds-read-access-TFPA-0022014.html

Thank Claire Robinson for validating it on Mageia 4 i586. Refer to:

https://bugs.mageia.org/show_bug.cgi?id=15567

(From OE-Core rev: 68994284f3c059b737bfc5afc2600ebd09bdf47f)

Signed-off-by: Junling Zheng <zhengjunling@huawei.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>