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Re: [PATCH v2] tftp.h: rework layout to work with fortification


On Thursday 12 April 2012 13:30:38 Mike Frysinger wrote:
> The current tftp structure does not work when fortification is enabled.
> Starting with gcc-4.5, more size checking was added to trigger these.
> Older versions just didn't have enough information, so they returned -1
> as the sizes.
> 
> First, the tu_stuff field is declared as 1 byte (when it's really an
> arbitrary length C string), so attempting to strcpy() with it results
> in crashes.  This fails with _FORTIFY_SOURCE=1.
> 
> Second, even if we change that to [0] (since gcc does not allow flexible
> array members in an union), gcc is not smart enough to see that they are
> two overlapping flexible arrays (tu_stuff and tu_data), so it will still
> trigger an abort with _FORTIFY_SOURCE=2.  This is because it thinks that
> tu_stuff is 0 bytes and tu_data comes after it.
> 
> Talking to upstream gcc, they don't seem terribly inclined to fix the
> 2nd issue, but even if they did, we still have plenty of 4.5 and 4.6
> installs that would hit problems.
> 
> So, let's re-order with a few more anonymous structs & unions so that
> the fields are laid out with a zero-length array always as the last
> field.  This seems to fix things with gcc-4.6, and the tftp-hpa pkg
> continues to build & work.

any complaints on this version ?
-mike

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