Re: [Xen-devel] [PATCH 04/14] fuzz/x86_emulate: Add a better input size check

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 25/08/17 17:43, George Dunlap wrote:
> For some reason the 'feof()' check for the file size isn't working in
> llvm-clang-fast mode; the result is several kilobyte files rather than
> the 4k limit files as we've requested.  This is bad in part because
> AFL will spend time trying to "fuzz" bits of the input that are never
> touched.
>
> Add a new check: Offer to read INPUT_SIZE + 1; if we actually get that
> many bytes, return an error.
>
> Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxx>

Doesn't fast mode pass the corpus by shared memory?  I wonder if it is
doing something slightly wonky with hooking the library functions.

Has this issue been reported upstream?  A workaround like this shouldn't
be necessary.

~Andrew

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