On Thu, Sep 21, 2023 at 02:53:30PM -0400, Liam R. Howlett wrote: > * Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> [230921 14:25]: > > On Thu, 21 Sep 2023 14:12:34 -0400 "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx> wrote: > > > > > Pedro Falcato contacted me on IRC with an mprotect regression which was > > > bisected back to the iterator changes for maple tree. Root cause > > > analysis showed the mas_prev() running off the end of the VMA space > > > (previous from 0) followed by mas_find(), would skip the first value. > > > > > > This patch set introduces maple state underflow/overflow so the sequence > > > of calls on the maple state will return what the user expects. > > > > It isn't clear what are the user-visible effects of this flaw? Please > > send this along and I'll paste it in. > > > User may notice that mas_prev() or mas_next() calls that result in going > outside of the limit passed to the call will cause incorrect returns on > subsequent calls using that maple state, such as mas_find() skipping an > entry. When Andrew says "User visible" he means "userspace visible". Not "in kernel user visible". What are the _consequences_. I'd say that if the user maps something at address 0, mprotect() can then fail to ... or something.
