[Bug gdb/30639] AddressSanitizer: dynamic-stack-buffer-overflow /home/root/sp/Dataset/Binutils/binutils_aflpp/gdb/ada-lang.c:1388:16 in ada_decode[abi:cxx11](char const*, bool, bool)

["keiths at redhat dot com" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=30639

Keith Seitz <keiths at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2023-08-15
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW

--- Comment #8 from Keith Seitz <keiths at redhat dot com> ---
My apologies, this DOES reproduce (as Tom notes). The thing I
ignored was ASAN. [The crash I reported was recently fixed by
Alan Modra's "gdb: warn unused result for bfd IO functions".]

[Probably TMI for Tom, but for anyone following along...]

In process_coff_symbol, we are processing a symbol with name "44",
i.e, just digits. The language of this objfile is language_unknown.

process_coff_symbol calls general_symbol_info::compute_and_set_names.
This eventually calls symbol_find_demangled_name with linkage_name_copy
set to "44". Since the objfile's language is unknown, symbol_find_linkage_name
iterates over all languages, calling the language's sniff_from_mangled_name
method. This does nothing for all the languages until it hits language_ada.

ada_language::sniff_from_mangled immediately calls ada_decode.

The code here essentially skips to the last block which attempts to
remove trailing digits:

1370   /* Remove trailing __{digit}+ or trailing ${digit}+.  */
1371
1372   if (len0 > 1 && isdigit (encoded[len0 - 1]))
1373     {
1374       i = len0 - 2;
1375       while ((i >= 0 && isdigit (encoded[i]))
1376              || (i >= 1 && encoded[i] == '_' && isdigit (encoded[i - 1])))
1377         i -= 1;
1378       if (i > 1 && encoded[i] == '_' && encoded[i - 1] == '_')
1379         len0 = i - 1;
1380       else if (encoded[i] == '$')
1381         len0 = i;
1382     }

When we get to 1372, len0 is strlen("44") which is 2. encoded[2 - 1] = "4" is
a digit, and we set i = len0 - 2 = 0.

Now the while loop: i == 0 and encoded[0] is "4", so that passes the first
test, and we subtract 1 from i, setting it to -1. Now i is no longer >= 0
or >= 1, so the while loop escapes. Finally, we hit the final "else if"
encoded[-1] == '$' on line 1380, which causes the observed buffer overflow.

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