bugThe FreeType Project - Bugs: bug #46313, Malformed pfr font spends much...


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bug #46313: Malformed pfr font spends much time in af_latin_hints_link_segments.

Submitter:  bungeman <bungeman>
Submitted:  Wed 28 Oct 2015 03:51:42 PM UTC
Severity:  3 - Normal Item Group:  None
Status:  Invalid Privacy:  Public
Assigned to:  wl Open/Closed:  Closed
Planned Release:  None

Wed 28 Oct 2015 06:40:54 PM UTC, comment #1: 

I've downloaded the original, unmodified file `AssLtts13.pfr', and it is indeed an abnormal font: The `.notdef' glyph (showing a lion in Assyrian style) has 4229 points!

Due to the fact that the fuzzer changes the internal scaling factor from 0.03 to 8 in your sample file, increasing the glyph sizes by a factor of 256, you get 576 horizontal segments instead of 30 in the original font, for example.

In other words, slow processing is expected for this malformed font, and I don't think we have a bug here.  Maybe you shouldn't use those Assyrian fonts for fuzzing...

Werner LEMBERG <wl>
Group administrator
Wed 28 Oct 2015 03:51:42 PM UTC, original submission:  

Found with libFuzzer, reproduction attached.

With the attached malformed pfr font, runinput takes about a half second. Profiling with perf indicates that this spends a great deal of time in af_latin_hints_link_segments and af_* generally. This may simply be expected behavior for a malformed font, but it seems like this is taking long enough that it should be understood why. This behavior has also dragged pfr fuzzing back down to an average of ~5 executions a second.

bungeman <bungeman>


(Note: upload size limit is set to 16384 kB, after insertion of the required escape characters.)

Attached Files
file #35326:  d2a8692b5b7453ef780108255b293e75014ea950 added by bungeman (66KiB - application/octet-stream)


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    Follow 5 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2015-10-28 wl Item GroupWishlist None
        StatusNone Invalid
        Assigned toNone wl
        Open/ClosedOpen Closed
    2015-10-28 bungeman Attached File- Added d2a8692b5b7453ef780108255b293e75014ea950, #35326

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