The patch titled Subject: mm/vmalloc: fix page mapping if vm_area_alloc_pages() with high order fallback to order 0 has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-vmalloc-fix-page-mapping-if-vm_area_alloc_pages-with-high-order-fallback-to-order-0.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Hailong Liu hailong.liu@oppo.com Subject: mm/vmalloc: fix page mapping if vm_area_alloc_pages() with high order fallback to order 0 Date: Thu, 8 Aug 2024 20:19:56 +0800

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.

Link: https://lkml.kernel.org/r/20240808122019.3361-1-hailong.liu@oppo.com Fixes: e9c3cda4d86e ("mm, vmalloc: fix high order __GFP_NOFAIL allocations") Signed-off-by: Hailong Liu hailong.liu@oppo.com Reported-by: Tangquan Zheng zhengtangquan@oppo.com Reviewed-by: Baoquan He bhe@redhat.com Reviewed-by: Uladzislau Rezki (Sony) urezki@gmail.com Acked-by: Barry Song baohua@kernel.org Cc: Matthew Wilcox willy@infradead.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/vmalloc.c | 11 ++--------- 1 file changed, 2 insertions(+), 9 deletions(-)

--- a/mm/vmalloc.c~mm-vmalloc-fix-page-mapping-if-vm_area_alloc_pages-with-high-order-fallback-to-order-0 +++ a/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;

/* * Higher order allocations must be able to be treated as _

Patches currently in -mm which might be from hailong.liu@oppo.com are

mm-vmalloc-fix-page-mapping-if-vm_area_alloc_pages-with-high-order-fallback-to-order-0.patch