Re: [hatari-devel] Patch to fix crash saving midi preferences on Mac

[Eero Tamminen <oak@xxxxxxxxxxxxxx>]

Hi,

On 28.5.2022 1.19, Chris Jenkins wrote:
> I hit another bug after building Hatari from the latest commit on master on
> my Mac. Please see the attached patch that fixes it for me.

Thanks for debugging and for the tested fix!


> *Steps to reproduce:*
> - Open the Mac preferences GUI
> - Click OK to close the preferences GUI again

(Unfortunately I do not have Mac to check this.)

> *Expected results:*
> - Preferences are saved
>
> *Actual results:*
> - Hatari crashes and prints the following:
> trace/BPT trap: 5
>
> It turns out that the code is supplying the wrong size to strncpy; it
> supplies FILENAME_MAX (which is 1024 on my Mac) whereas the length of the
> field is MAX_MIDI_PORT_NAME (256). It looks like this is a similar problem
> to the one that was fixed in
> commit b8b80c4d6b8f342516479a927d831218d82cf2f0 but in a different part of
> the code.

Ok, so that header change in b8b80c4d broke it.


> Note that I didn't expect this to crash, given that the text that is being
> copied in this case is "Off" which isn't anywhere near 256 characters long.
> I guess Apple decided that their strncpy function should blow up if the
> size of the buffer is less than the num parameter. Running this in the
> debugger shows that it hits a brk instruction in a function called
> __chk_fail_overflow.so it looks deliberate.

That could also explain the reported crash, which b8b80c4d6 is trying to 
fix.


> Please let me know if the patch looks ok and if I can do anything else on
> this.

Could you change your patch to use sizeof() and strlcpy() like the 
commit b8b80c4d6 does (to make it more robust and smaller), test that it 
still works, and send it to list / me?


	- Eero