Possibly incorrect allocation in function pp_alloc_clr

[nkosmatov]

While working on formal verification of cache coloring and page coloring mechanisms in Bao, we discovered two issues in function pp_alloc_clr

The following line (currently line 138 in commit c306b0f in file src/core/mmu/mem.c)
index ++;

should be removed. Otherwise , in some situations, a previously allocated page can be allocated again, or other unintended behavior can occur.

The following line (currently line 161 in commit c306b0f in file src/core/mmu/mem.c)
index = 0;
should be replaced by
index = pp_next_clr ( pool->base , 0 , colors ) ;
Otherwise , in some situations, a previously allocated page can be allocated again.

After the proposed modifications we were able to prove a (slightly simplified) corrected version of cache coloring and page coloring mechanisms in Bao.

[josecm]

Hello @nkosmatov!

After the proposed modifications we were able to prove a (slightly simplified) corrected version of cache coloring and page coloring mechanisms in Bao.

This is amazing!! Thank you for doing that work.

Your corrections seem to make sense. I'd propose you send a PR with the fixes you point out.

[josecm]

Fixed by #202