linux-kernel - [PATCH v1] mm/vmalloc: fix page mapping if vm_area_alloc_pages() with high order fallback to order 0

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Message-ID: <20240808120121.2878-1-hailong.liu@oppo.com>
Date: Thu, 8 Aug 2024 20:00:58 +0800
From: Hailong Liu <hailong.liu@...o.com>
To: Andrew Morton <akpm@...ux-foundation.org>, Uladzislau Rezki
	<urezki@...il.com>, Christoph Hellwig <hch@...radead.org>, Vlastimil Babka
	<vbabka@...e.cz>, Michal Hocko <mhocko@...e.com>
CC: Hailong Liu <hailong.liu@...o.com>, "Tangquan . Zheng"
	<zhengtangquan@...o.com>, <stable@...r.kernel.org>, Barry Song
	<21cnbao@...il.com>, Baoquan He <bhe@...hat.com>, Matthew Wilcox
	<willy@...radead.org>, <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>
Subject: [PATCH v1] mm/vmalloc: fix page mapping if vm_area_alloc_pages() with high order fallback to order 0

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@...o.com>
Reported-by: Tangquan.Zheng <zhengtangquan@...o.com>
Cc: <stable@...r.kernel.org>
CC: Barry Song <21cnbao@...il.com>
CC: Baoquan He <bhe@...hat.com>
CC: Matthew Wilcox <willy@...radead.org>
---
 mm/vmalloc.c     | 11 ++---------
 mm/vmalloc.c.rej | 10 ++++++++++
 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;

 		/*
 		 * Higher order allocations must be able to be treated as
diff --git a/mm/vmalloc.c.rej b/mm/vmalloc.c.rej
new file mode 100644
index 000000000000..c28017088319
--- /dev/null
+++ b/mm/vmalloc.c.rej
@@ -0,0 +1,10 @@
+--- mm/vmalloc.c
++++ mm/vmalloc.c
+@@ -3000,6 +3005,7 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
+ 	unsigned int nr_allocated = 0;
+ 	gfp_t alloc_gfp = gfp;
+ 	bool nofail = false;
++	bool fallback = false;
+ 	struct page *page;
+ 	int i;
+
---
Baoquan suggests set page_shift to 0 if fallback in (2 and concern about
performance of retry with order-0. But IMO with retry,
- Save memory usage if high order allocation failed.
- Keep consistancy with align and page-shift.
- make use of bulk allocator with order-0

[2] https://lore.kernel.org/lkml/20240725035318.471-1-hailong.liu@oppo.com/
--
2.34.1