3 ms·

I found a 271,800 character demangled symbol name in libmshr

7 points by AntiRush 5y ago

bombcar 5y ago
Well what was it?
- teh_klev 5y ago
  I know it's annoying, even the article doesn't reveal to us what it is: The longest demangled ELF symbol is 271,800 characters and is defined in the file usr/lib/x86_64-linux-gnu/libmshr.so.2019.2.0.dev0 provided by the libmshr2019.2 package. Sadly this submission is a victim of the wrong kind of title editorialising.
  - st_goliath 5y ago
    I tried to go looking for myself, so I downloaded the AMD64 binary from the Debian page: https://packages.debian.org/unstable/libmshr2019.2 https://packages.debian.org/unstable/libmshr2019.2 After unpacking the data.tar.xz from the deb archive, I unpacked libmshr.so.2019.2.0.dev0 from the specified path. Doing this: readelf -W --demangle=c++ -s libmshr.so.2019.2.0.dev0 | awk ' { if ( length > x ) { x = length; y = $0 } }END{ print y }' > test.txt gave me a text file that is 101,943 bytes in size. Basically a huge C++ template soup, but still quite a bit short from the 271,800 bytes in the headline. If you want to see it, I compressed (568 bytes!) and base64 encoded it: xz test.txt base64 test.txt.xz And uploaded it here: https://paste.debian.net/1237184/ https://paste.debian.net/1237184/ Which can be viewed with this one liner: curl https://paste.debian.net/download/1237184 | base64 -d | xz -d
    - teh_klev 5y ago
      Thank you. It's the wee hours here and frankly I just didn't have the energy to do it myself.
teh_klev 5y ago
Please don't editorialise article submission titles. Even from the bullet point which you cherry picked to use as the title doesn't tell us anything useful other than it's a 271,800 character symbol. https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html
- dataangel 5y ago
  Umm... A symbol this long is very surprising and interesting. How is this editorializing? It's also a real quote from the linked post.
rurban 5y ago
more interesting would be homoglyphs in C or C++ ABI's, eg by assuming UTF-8 encodings. or at least utf-8 names in the wild. the overlong symbol looks it's coming from here: https://github.com/martinal/mshr/blob/master/src/Polyhedral_multicomponent_mesh_domain_with_features_3.h https://github.com/martinal/mshr/blob/master/src/Polyhedral_... so not an overflow attack, just C++ nonsense.

7 points by AntiRush 5y ago

bombcar 5y ago

Well what was it?

teh_klev 5y ago
I know it's annoying, even the article doesn't reveal to us what it is: The longest demangled ELF symbol is 271,800 characters and is defined in the file usr/lib/x86_64-linux-gnu/libmshr.so.2019.2.0.dev0 provided by the libmshr2019.2 package. Sadly this submission is a victim of the wrong kind of title editorialising.
- st_goliath 5y ago
  I tried to go looking for myself, so I downloaded the AMD64 binary from the Debian page: https://packages.debian.org/unstable/libmshr2019.2 https://packages.debian.org/unstable/libmshr2019.2 After unpacking the data.tar.xz from the deb archive, I unpacked libmshr.so.2019.2.0.dev0 from the specified path. Doing this: readelf -W --demangle=c++ -s libmshr.so.2019.2.0.dev0 | awk ' { if ( length > x ) { x = length; y = $0 } }END{ print y }' > test.txt gave me a text file that is 101,943 bytes in size. Basically a huge C++ template soup, but still quite a bit short from the 271,800 bytes in the headline. If you want to see it, I compressed (568 bytes!) and base64 encoded it: xz test.txt base64 test.txt.xz And uploaded it here: https://paste.debian.net/1237184/ https://paste.debian.net/1237184/ Which can be viewed with this one liner: curl https://paste.debian.net/download/1237184 | base64 -d | xz -d
  - teh_klev 5y ago
    Thank you. It's the wee hours here and frankly I just didn't have the energy to do it myself.

teh_klev 5y ago

Please don't editorialise article submission titles. Even from the bullet point which you cherry picked to use as the title doesn't tell us anything useful other than it's a 271,800 character symbol. https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html

dataangel 5y ago
Umm... A symbol this long is very surprising and interesting. How is this editorializing? It's also a real quote from the linked post.

rurban 5y ago

more interesting would be homoglyphs in C or C++ ABI's, eg by assuming UTF-8 encodings. or at least utf-8 names in the wild. the overlong symbol looks it's coming from here: https://github.com/martinal/mshr/blob/master/src/Polyhedral_multicomponent_mesh_domain_with_features_3.h https://github.com/martinal/mshr/blob/master/src/Polyhedral_... so not an overflow attack, just C++ nonsense.