bugThe FreeType Project - Bugs: bug #45938, src/winfonts/winfnt.c:382:61:...


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bug #45938: src/winfonts/winfnt.c:382:61: runtime error: shift exponent 2816 is too large for 64-bit type 'FT_ULong'

Submitter:  Kostya Serebryany <kcc>
Submitted:  Fri 11 Sep 2015 09:43:55 PM UTC
Severity:  3 - Normal Item Group:  None
Status:  Fixed Privacy:  Public
Assigned to:  wl Open/Closed:  Closed
Planned Release:  2.6.1

Sun 13 Sep 2015 07:22:39 AM UTC, comment #1: 

Fixed in git, thanks!

Werner LEMBERG <wl>
Group administrator
Fri 11 Sep 2015 09:43:55 PM UTC, original submission:  

found on fresh git with libFuzzer+UBSan

Build with ubsan (clang -fsanitize=shift).
Feed the data below (base64-encoded) into FT_New_Memory_Face

src/winfonts/winfnt.c:381:61: runtime error: shift exponent 2816 is too large for 64-bit type 'FT_ULong' (aka 'unsigned long')

Indeed, this code is:
        size_shift = FT_GET_USHORT_LE();
        face->font->offset   = (FT_ULong)FT_GET_USHORT_LE() << size_shift;

i.e. the bytes taken directly from the user input are used for the shift exponent.
in C/C++, shifting a 64-bit value by more than 63 is undefined behavior.


Kostya Serebryany <kcc>
Group Member


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    Follow 4 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2015-09-13 wl StatusNone Fixed
        Assigned toNone wl
        Open/ClosedOpen Closed
        Planned ReleaseNone 2.6.1

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