Heap buffer underflow in find_argv_from_env

[itamaro]

When running one of our applications that uses setproctitle under clang ASAN, it detected a heap buffer underflow in find_argv_from_env.

This gist (and this godbolt) demonstrate the issue using a minimal test program that copies find_argv_from_env with minor modifications to build standalone.

when running with one arg (e.g. ./test 1) it fires on if (*ptr) ..., and when running with no args (e.g. ./test) it fires on if (strcmp(ptr, arg0)) ....

The gist includes the full output from both runs.

[dvarrazzo]

Will look into that, thank you for the report.

If you would like to provide a MR, as you have these tools already set up, it would be welcome.

[itamaro]

If you would like to provide a MR, as you have these tools already set up, it would be welcome.

I'd be happy to send one, but I don't know how to fix the issue :)
If you have guidance, I can give it a try and test again