strlen() and NULL pointer checks

[Jeff Morriss <jeff.morriss.ws () gmail com>]

Hi folks,

Every once in a while, I do some fuzz testing on a Solaris/SPARC system. 
 When I first did it I was primarily worried about getting bus errors 
(due to casts increasing alignment requirements), but usually what I 
find is another case of what I fixed in r37181.  (Fortunately, I have 
not gotten bus errors.)

The backtrace for that one was:

> #0  0xfc4b2150 in strlen () from /usr/lib/libc.so.1
> #1  0xfc51d704 in _ndoprnt () from /usr/lib/libc.so.1
> #2  0xfc51fe24 in vsnprintf () from /usr/lib/libc.so.1
> #3  0xfd19c07c in proto_tree_set_representation_value (pi=0xff850be8, format=0xfe6d2c48 "(%s) Type %u: Value (hex bytes): %s", 
>     ap=0xffbfdb50) at /Wireshark/source/epan/proto.c:3651
> #4  0xfd190184 in proto_tree_add_bytes_format_value (tree=0xff850ba0, hfindex=48268, tvb=0x507e84, start=210, length=4, start_ptr=0x0, 
>     format=0xfe6d2c48 "(%s) Type %u: Value (hex bytes): %s") at /Wireshark/source/epan/proto.c:1908
> #5  0xfd8ab260 in dissect_v9_v10_pdu_data (tvb=0x507e84, pinfo=0xffbff1c8, pdutree=0xff850ba0, offset=210, tplt=0xff461a10, 
>     hdrinfo=0xffbfdee0, fields_type=TF_ENTRIES) at /Wireshark/source/epan/dissectors/packet-netflow.c:4791


The basic problem is that Solaris' strlen() seg-faults if given a NULL 
pointer whereas a lot of other implementations just return 0. 
Unfortunately glib does not appear to provide a safe alternative.

To avoid me being the only one doing this test, I have half-seriously 
contemplated:

1) building a version of strlen() which seg-faults when given a NULL pointer
2) building it into a shared library
3) using LD_PRELOAD to use this library when fuzz testing (at least on 
systems that support LD_PRELOAD)

Is there a better way?  Or better yet, a proper solution?

Regards,
-Jeff
___________________________________________________________________________
Sent via:    Wireshark-dev mailing list <wireshark-dev () wireshark org>
Archives:    http://www.wireshark.org/lists/wireshark-dev
Unsubscribe: https://wireshark.org/mailman/options/wireshark-dev
            mailto:wireshark-dev-request () wireshark org?subject=unsubscribe