Current heap size in stage2 is three pages long [0x6000-0x9000] but
get_zeroed_page() assumes it is one page more which might lead to
a heap overflow which will corrupt data located at 0x9000 (stage3
parameters). Calculate the heap size of a stage at run-time
by using the symbols provided by linker.
Furthermore, validate the given address in free_page() to stop illegal
memory accesses.
Signed-off-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Reviewed-by: Philipp Rudo <prudo@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>
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