Comment # 14
on bug 8197
from Evan Huus
(In reply to comment #13)
> (In reply to comment #9)
> > I get the crash in Fedora 17. Valgrind complains thus:
> >
> > ~~~
> > ==1239== Command: /home/morriss/Projects/wireshark/source2/.libs/lt-tshark
> > -Vx -nr /tmp/fuzz-8197.pcap
> > ==1239==
> > ==1239== Invalid read of size 1
> > ==1239== at 0x4104D5: print_hex_data_buffer (print.c:997)
> > ==1239== by 0x411E48: print_hex_data (print.c:915)
> > ==1239== by 0x4197B6: print_packet (tshark.c:3589)
> > ==1239== by 0x41AFAD: process_packet (tshark.c:3198)
> > ==1239== by 0x40DE9A: main (tshark.c:2978)
> > ==1239== Address 0x9216800 is 0 bytes inside a block of size 1 free'd
> > ==1239== at 0x4A07786: free (vg_replace_malloc.c:446)
> > ==1239== by 0x35ACC4D50E: g_free (in /usr/lib64/libglib-2.0.so.0.3200.4)
> > ==1239== by 0x613ECDB: emem_free_all (emem.c:1239)
> > ==1239== by 0x6141828: epan_dissect_run_with_taps (epan.c:218)
> > ==1239== by 0x41AEAC: process_packet (tshark.c:3181)
> > ==1239== by 0x40DE9A: main (tshark.c:2978)
>
> >
> > The first ("invalid read of size 1") is because tvb_new_octet_aligned() is
> > returning an ep_alloc'd buffer which is then being added as a data source
> > (add_new_data_source()). I still need to go back and read about why ep_
> > allocations started disappearing after dissection is complete but before
> > we're done displaying what we've dissected. Anyway, this isn't causing the
> > crash.
>
> The correct fix for this particular issue (although it is basically a
> non-issue in practice due to some emem/wmem internals) is to have
> tvb_new_octet_aligned use the pinfo-scoped pool (pinfo->pool) instead of
> ephemeral or packet-scoped memory. Unfortunately, this will require passing
> pinfo pointers into all sorts of functions that don't already have them (in
> the PER dissector at least) so isn't a simple change.
More precisely, tvb_new_octet_aligned should take a wmem allocator as a
parameter and use that to allocate the buffer. The PER dissector (and
presumably others using this pattern) should be passing in the pinfo pool to
that parameter.
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