Re: [Xen-devel] [PATCH v3 01/12] fuzz/x86_emulate: Clear errors after each iteration

[George Dunlap <george.dunlap@xxxxxxxxxx>]

On 10/10/2017 05:20 PM, George Dunlap wrote:
> Once feof() returns true for a stream, it will continue to return true
> for that stream until clearerr() is called (or the stream is closed
> and re-opened).
> 
> In llvm-clang-fast-mode, the same file descriptor is used for each
> iteration of the loop, meaning that the "Input too large" check was
> broken -- feof() would return true even if the fread() hadn't hit the
> end of the file.  The result is that AFL generates testcases of
> arbitrary size.
> 
> Fix this by fseek'ing to the beginning of the file on every iteration;
> this resets the EOF marker and other state.
> 
> Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxx>
> ---
> Changes in v3:
> - Fix the issue in the official sanctioned way

Hmm, seems v2 of this patch was checked in; review had flagged up that
"clearerr()" was too big of a hammer.

Attached is a revised v1/12 patch that fixes this.

 -George

Attachment: 0001-fuzz-x86_emulate-Clear-errors-in-the-officially-sanc.patch
Description: Text Data

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