Jeff Xu <jeffxu@xxxxxxxxxxxx> wrote: > > > + replacement with a new mapping with new set of attributes, or can > > > + overwrite the existing mapping with another mapping. > > > + > > > + mprotect and pkey_mprotect are blocked because they changes the > > > + protection bits (RWX) of the mapping. > > > + > > > + Some destructive madvise behaviors (MADV_DONTNEED, MADV_FREE,> + MADV_DONTNEED_LOCKED, MADV_FREE, MADV_DONTFORK, MADV_WIPEONFORK) > > > + for anonymous memory, when users don't have write permission to the > > > + memory. Those behaviors can alter region contents by discarding pages, > > > > above is not a sentence but I don't know how to fix it. > > > Would below work ? > > Certain destructive madvise behaviors, specifically MADV_DONTNEED, > MADV_FREE, MADV_DONTNEED_LOCKED, MADV_FREE, MADV_DONTFORK, > MADV_WIPEONFORK, can pose risks when applied to anonymous memory by > threads without write permissions. These behaviors have the potential > to modify region contents by discarding pages, effectively performing > a memset(0) operation on the anonymous memory. In OpenBSD, mimmutable blocks all those madvise() operations. I don't understand the sentence supplied above. Is it saying that mseal() solves that problem, or that mseal() does not solve that problem. I would hope it solves that problem. But the sentence explains the problem without taking a position on what to do.
