[cairo-bugs] [Bug 90120] New: Image compositor can pass invalid coordinates to pixman_fill()

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=90120

            Bug ID: 90120
           Summary: Image compositor can pass invalid coordinates to
                    pixman_fill()
           Product: cairo
           Version: unspecified
          Hardware: Other
                OS: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: general
          Assignee: chris at chris-wilson.co.uk
          Reporter: federico at gnome.org
        QA Contact: cairo-bugs at cairographics.org

See https://bugzilla.gnome.org/show_bug.cgi?id=744391 for where this comes
from.

Summary: librsvg gets an SVG generated through fuzz-testing, and passes big
coordinates that give problems to Cairo.  In turn, Cairo ends up passing
invalid coordinates to pixman_fill(), which does an out-of-bounds write.

Pixman doesn't validate the arguments passed to pixman_fill().

Given that Cairo's problems with big coordinates and fixed-point overflow are
Hard To Fix(tm), we can make Cairo at least responsible for not passing invalid
coordinates to pixman's low-level machinery.

The attached patch takes care of the call to pixman_fill() from this particular
code path.  I haven't gotten reports of other invalid calls to pixman_fill()
from Cairo/librsvg.

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