The pathfind from bkloppenborg

Pathfind won't detect OS on Alpine Linux

Line 88 in d822a2f

#elif defined (__gnu_linux__) // Linux

__gnu_linux__ isn't defined on Alpine, just __linux__.

Buffer overread in do_readlink

Hi,

on many systems, the current implementation of do_readlink may cause a random read into uninitialized memory.

do_readlink currently directly converts the return value of readlink into a std::string. However, the return of readlink is not null-terminated. Hence, when you don't use the length returned by readlink and have a system that does not pre-initialize a buffer with 0-bytes, memory will be read until randomly encountering a null-byte.

Reproducible with this program:

#include <iostream>
#include <PathFind.hpp>

int main()
{
	std::cout << do_readlink("./test") << std::endl;
	return 0;
}

With linking ./test to /, on ubuntu 20.04 with gcc 9.3.0 this yields output like:

$./a.out
/��GT�

Valgrind output:

$ valgrind ./a.out
==2418761== Memcheck, a memory error detector
==2418761== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==2418761== Using Valgrind-3.15.0 and LibVEX; rerun with -h for copyright info
==2418761== Command: ./a.out
==2418761==
==2418761== Conditional jump or move depends on uninitialised value(s)
==2418761==    at 0x10A865: std::char_traits<char>::length(char const*) (in .../pathfind/src/a.out)
==2418761==    by 0x10A978: std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::basic_string<std::allocator<char> >(char const*, std::allocator<char> const&) (in .../pathfind/src/a.out)
==2418761==    by 0x10A6CE: do_readlink(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) (in .../pathfind/src/a.out)
==2418761==    by 0x10AC52: main (in .../pathfind/src/a.out)
==2418761==
==2418761== Conditional jump or move depends on uninitialised value(s)
==2418761==    at 0x4AE3F5D: _IO_file_overflow@@GLIBC_2.2.5 (fileops.c:783)
==2418761==    by 0x4AE51A3: _IO_default_xsputn (genops.c:399)
==2418761==    by 0x4AE51A3: _IO_default_xsputn (genops.c:370)
==2418761==    by 0x4AE2879: _IO_new_file_xsputn (fileops.c:1265)
==2418761==    by 0x4AE2879: _IO_file_xsputn@@GLIBC_2.2.5 (fileops.c:1197)
==2418761==    by 0x4AD6540: fwrite (iofwrite.c:39)
==2418761==    by 0x49879B3: std::basic_ostream<char, std::char_traits<char> >& std::__ostream_insert<char, std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*, long) (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.28)
==2418761==    by 0x10AC65: main (in .../pathfind/src/a.out)
==2418761==
==2418761== Syscall param write(buf) points to uninitialised byte(s)
==2418761==    at 0x4B611E7: write (write.c:26)
==2418761==    by 0x4AE200C: _IO_file_write@@GLIBC_2.2.5 (fileops.c:1181)
==2418761==    by 0x4AE3AD0: new_do_write (fileops.c:449)
==2418761==    by 0x4AE3AD0: _IO_new_do_write (fileops.c:426)
==2418761==    by 0x4AE3AD0: _IO_do_write@@GLIBC_2.2.5 (fileops.c:423)
==2418761==    by 0x4AE4012: _IO_file_overflow@@GLIBC_2.2.5 (fileops.c:784)
==2418761==    by 0x4987478: std::ostream::put(char) (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.28)
==2418761==    by 0x49876A7: std::basic_ostream<char, std::char_traits<char> >& std::endl<char, std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&) (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.28)
==2418761==    by 0x10AC7A: main (in .../pathfind/src/a.out)
==2418761==  Address 0x4da7c81 is 1 bytes inside a block of size 1,024 alloc'd
==2418761==    at 0x483B7F3: malloc (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
==2418761==    by 0x4AD4E83: _IO_file_doallocate (filedoalloc.c:101)
==2418761==    by 0x4AE504F: _IO_doallocbuf (genops.c:347)
==2418761==    by 0x4AE40AF: _IO_file_overflow@@GLIBC_2.2.5 (fileops.c:745)
==2418761==    by 0x4AE2834: _IO_new_file_xsputn (fileops.c:1244)
==2418761==    by 0x4AE2834: _IO_file_xsputn@@GLIBC_2.2.5 (fileops.c:1197)
==2418761==    by 0x4AD6540: fwrite (iofwrite.c:39)
==2418761==    by 0x49879B3: std::basic_ostream<char, std::char_traits<char> >& std::__ostream_insert<char, std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*, long) (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.28)
==2418761==    by 0x10AC65: main (in .../pathfind/src/a.out)
==2418761==
/
==2418761==
==2418761== HEAP SUMMARY:
==2418761==     in use at exit: 0 bytes in 0 blocks
==2418761==   total heap usage: 2 allocs, 2 frees, 73,728 bytes allocated
==2418761==
==2418761== All heap blocks were freed -- no leaks are possible
==2418761==
==2418761== Use --track-origins=yes to see where uninitialised values come from
==2418761== For lists of detected and suppressed errors, rerun with: -s
==2418761== ERROR SUMMARY: 4 errors from 3 contexts (suppressed: 0 from 0)

This also means that the output of any function using do_readlink may be incorrect.

bkloppenborg / pathfind Goto Github PK

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Pathfind won't detect OS on Alpine Linux

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