On Fri 09-08-24 11:30:32, Michal Hocko wrote:
> On Thu 08-08-24 20:00:58, Hailong Liu wrote:
> > The __vmap_pages_range_noflush() assumes its argument pages** contains
> > pages with the same page shift. However, since commit e9c3cda4d86e
> > (mm, vmalloc: fix high order __GFP_NOFAIL allocations), if gfp_flags
> > includes __GFP_NOFAIL with high order in vm_area_alloc_pages()
> > and page allocation failed for high order, the pages** may contain
> > two different page shifts (high order and order-0). This could
> > lead __vmap_pages_range_noflush() to perform incorrect mappings,
> > potentially resulting in memory corruption.
> >
> > Users might encounter this as follows (vmap_allow_huge = true, 2M is for PMD_SIZE):
> > kvmalloc(2M, __GFP_NOFAIL|GFP_X)
> > __vmalloc_node_range_noprof(vm_flags=VM_ALLOW_HUGE_VMAP)
> > vm_area_alloc_pages(order=9) ---> order-9 allocation failed and fallback to order-0
> > vmap_pages_range()
> > vmap_pages_range_noflush()
> > __vmap_pages_range_noflush(page_shift = 21) ----> wrong mapping happens
> >
> > We can remove the fallback code because if a high-order
> > allocation fails, __vmalloc_node_range_noprof() will retry with
> > order-0. Therefore, it is unnecessary to fallback to order-0
> > here. Therefore, fix this by removing the fallback code.
> >
> > Fixes: e9c3cda4d86e ("mm, vmalloc: fix high order __GFP_NOFAIL allocations")
> > Signed-off-by: Hailong Liu <hailong.liu@xxxxxxxx>
> > Reported-by: Tangquan.Zheng <zhengtangquan@xxxxxxxx>
> > Cc: <stable@xxxxxxxxxxxxxxx>
> > CC: Barry Song <21cnbao@xxxxxxxxx>
> > CC: Baoquan He <bhe@xxxxxxxxxx>
> > CC: Matthew Wilcox <willy@xxxxxxxxxxxxx>
> > ---
> > mm/vmalloc.c | 11 ++---------
> > mm/vmalloc.c.rej | 10 ++++++++++
>
> What is this?
>
> > 2 files changed, 12 insertions(+), 9 deletions(-)
> > create mode 100644 mm/vmalloc.c.rej
> >
> > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> > index 6b783baf12a1..af2de36549d6 100644
> > --- a/mm/vmalloc.c
> > +++ b/mm/vmalloc.c
> > @@ -3584,15 +3584,8 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
> > page = alloc_pages_noprof(alloc_gfp, order);
> > else
> > page = alloc_pages_node_noprof(nid, alloc_gfp, order);
> > - if (unlikely(!page)) {
> > - if (!nofail)
> > - break;
> > -
> > - /* fall back to the zero order allocations */
> > - alloc_gfp |= __GFP_NOFAIL;
> > - order = 0;
> > - continue;
> > - }
> > + if (unlikely(!page))
> > + break;
>
> This just makes the NOFAIL allocation fail. So this is not a correct
> fix.
OK, I can see a newer version
--
Michal Hocko
SUSE Labs
