RTEMS 5.1 pc686 BSP malloc_info problem?

[Sebastian Huber]

Hello Alan,

On 09/10/2020 22:35, Alan Cudmore wrote:
> After doing a lot of tracing through my application, it looks like
> malloc_info works fine before we start our cFS application, but it
> blocks after the cFS is initialized. This suggests some sort of memory
> corruption.
> I started by instrumenting our code to call malloc info during various
> stages of application initialization, and finally narrowed it down to
> the code where we create a RAM Disk and format it with RFS.
> (skipping a bunch of other malloc based troubleshooting.. )
> After I followed the issue into the RFS init, I was able to narrow
> down the place where malloc_info stopped working to here:
> https://git.rtems.org/rtems/tree/cpukit/libfs/src/rfs/rtems-rfs-bitmaps.c?h=5#n637
> During the RFS format process.
> In this section of the code, the size variable is 0, meaning it will
> exit the for loop and then return from the function, but it increments
> the "search_map" variable and writes to memory through the pointer one
> more time before exiting the loop and function. It's at this point
> where malloc_info starts blocking.
>
> It seems to me that this if block should be skipped when size == 0. I
> tried that and the malloc_info issue seems to be fixed.
>
> Is this an RFS bug writing into other memory, or is this last write
> needed before the function updates?
>
> If this looks like a bug, should I write a ticket and provide a patch?
you can check heap overwrites like this automatically if you enable 
RTEMS_DEBUG.