[Nasm-bugs] [Bug 3392507] memory corruption of nasm when handling a crafed file due to function assemble_file(inname, depend_ptr) at asm/nasm.c:482

noreply-nasm at gorcunov.org noreply-nasm at gorcunov.org
Wed Sep 26 12:54:25 PDT 2018


--- Comment #4 from Scott Gayou <sgayou at redhat.com> ---
This appears to be due to the following pattern in preproc.c:

tt = tokenize(tline->text);
tt = expand_smacro(tt);
size = parse_size(tt->text);

In this case, expand_smacro errors out. ->text is set to NULL, and -> type is
set to TOK_WHITESPACE. We then call parse_size with NULL. No NULL checks occur
inside, and we eventually crash when trying to dereference null inside of
bsii's stricmp call.

This same pattern also appears in the case of PP_ARG. Thus, we can create a
similar reproducer via crafting a file with %arg instead of %local. Both
reproducers are attached (I have drastically reduced the reproducers to the
minimal crash case I believe).

Sorry about not submitting a patch -- I don't have enough nasm experience to
know what error behavior should happen in this case. (i.e. abort, continue,

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