linux-kernel - [PATCH v3 1/4] mm: vmalloc must set pte via arch code

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Date:   Fri,  2 Jun 2023 10:29:46 +0100
From:   Ryan Roberts <ryan.roberts@....com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        SeongJae Park <sj@...nel.org>,
        Christoph Hellwig <hch@...radead.org>
Cc:     Ryan Roberts <ryan.roberts@....com>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Lorenzo Stoakes <lstoakes@...il.com>,
        Uladzislau Rezki <urezki@...il.com>, Zi Yan <ziy@...dia.com>,
        Yu Zhao <yuzhao@...gle.com>, Mike Rapoport <rppt@...nel.org>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        damon@...ts.linux.dev, Christoph Hellwig <hch@....de>
Subject: [PATCH v3 1/4] mm: vmalloc must set pte via arch code

It is bad practice to directly set pte entries within a pte table.
Instead all modifications must go through arch-provided helpers such as
set_pte_at() to give the arch code visibility and allow it to check
(and potentially modify) the operation.

Fixes: 3e9a9e256b1e ("mm: add a vmap_pfn function")
Signed-off-by: Ryan Roberts <ryan.roberts@....com>
Reviewed-by: Zi Yan <ziy@...dia.com>
Acked-by: Lorenzo Stoakes <lstoakes@...il.com>
Reviewed-by: Christoph Hellwig <hch@....de>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@...il.com>
Reviewed-by: Mike Rapoport (IBM) <rppt@...nel.org>
---
 mm/vmalloc.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 9683573f1225..48202ec5f79a 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2899,10 +2899,16 @@ struct vmap_pfn_data {
 static int vmap_pfn_apply(pte_t *pte, unsigned long addr, void *private)
 {
 	struct vmap_pfn_data *data = private;
+	unsigned long pfn = data->pfns[data->idx];
+	pte_t ptent;
 
-	if (WARN_ON_ONCE(pfn_valid(data->pfns[data->idx])))
+	if (WARN_ON_ONCE(pfn_valid(pfn)))
 		return -EINVAL;
-	*pte = pte_mkspecial(pfn_pte(data->pfns[data->idx++], data->prot));
+
+	ptent = pte_mkspecial(pfn_pte(pfn, data->prot));
+	set_pte_at(&init_mm, addr, pte, ptent);
+
+	data->idx++;
 	return 0;
 }
 
-- 
2.25.1