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authorHugh Dickins2023-06-08 18:18:49 -0700
committerAndrew Morton2023-06-19 16:19:14 -0700
commitbe872f83bf571f4f9a0ac25e2c9c36e905a36619 (patch)
treede0eabc968377f347394dca48b93dbebe79d938d /mm
parent7780d04046a2288ab85d88bedacc60fa4fad9971 (diff)
mm/pagewalk: walk_pte_range() allow for pte_offset_map()
walk_pte_range() has a no_vma option to serve walk_page_range_novma(). I don't know of any problem, but it looks safer to check for init_mm, and use pte_offset_kernel() rather than pte_offset_map() in that case: pte_offset_map()'s pmdval validation is intended for userspace. Allow for its pte_offset_map() or pte_offset_map_lock() to fail, and retry with ACTION_AGAIN if so. Add a second check for ACTION_AGAIN in walk_pmd_range(), to catch it after return from walk_pte_range(). Remove the pmd_trans_unstable() check after split_huge_pmd() in walk_pmd_range(): walk_pte_range() now handles those cases safely (and they must fail powerpc's is_hugepd() check). Link: https://lkml.kernel.org/r/3eba6f0-2b-fb66-6bb6-2ee8533e221@google.com Signed-off-by: Hugh Dickins <hughd@google.com> Cc: Alistair Popple <apopple@nvidia.com> Cc: Anshuman Khandual <anshuman.khandual@arm.com> Cc: Axel Rasmussen <axelrasmussen@google.com> Cc: Christophe Leroy <christophe.leroy@csgroup.eu> Cc: Christoph Hellwig <hch@infradead.org> Cc: David Hildenbrand <david@redhat.com> Cc: "Huang, Ying" <ying.huang@intel.com> Cc: Ira Weiny <ira.weiny@intel.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Lorenzo Stoakes <lstoakes@gmail.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Miaohe Lin <linmiaohe@huawei.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Mike Rapoport (IBM) <rppt@kernel.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Naoya Horiguchi <naoya.horiguchi@nec.com> Cc: Pavel Tatashin <pasha.tatashin@soleen.com> Cc: Peter Xu <peterx@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Qi Zheng <zhengqi.arch@bytedance.com> Cc: Ralph Campbell <rcampbell@nvidia.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: SeongJae Park <sj@kernel.org> Cc: Song Liu <song@kernel.org> Cc: Steven Price <steven.price@arm.com> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com> Cc: Will Deacon <will@kernel.org> Cc: Yang Shi <shy828301@gmail.com> Cc: Yu Zhao <yuzhao@google.com> Cc: Zack Rusin <zackr@vmware.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/pagewalk.c33
1 files changed, 23 insertions, 10 deletions
diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index cb23f8a15c13..64437105fe0d 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -46,15 +46,27 @@ static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
spinlock_t *ptl;
if (walk->no_vma) {
- pte = pte_offset_map(pmd, addr);
- err = walk_pte_range_inner(pte, addr, end, walk);
- pte_unmap(pte);
+ /*
+ * pte_offset_map() might apply user-specific validation.
+ */
+ if (walk->mm == &init_mm)
+ pte = pte_offset_kernel(pmd, addr);
+ else
+ pte = pte_offset_map(pmd, addr);
+ if (pte) {
+ err = walk_pte_range_inner(pte, addr, end, walk);
+ if (walk->mm != &init_mm)
+ pte_unmap(pte);
+ }
} else {
pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
- err = walk_pte_range_inner(pte, addr, end, walk);
- pte_unmap_unlock(pte, ptl);
+ if (pte) {
+ err = walk_pte_range_inner(pte, addr, end, walk);
+ pte_unmap_unlock(pte, ptl);
+ }
}
-
+ if (!pte)
+ walk->action = ACTION_AGAIN;
return err;
}
@@ -141,11 +153,8 @@ again:
!(ops->pte_entry))
continue;
- if (walk->vma) {
+ if (walk->vma)
split_huge_pmd(walk->vma, pmd, addr);
- if (pmd_trans_unstable(pmd))
- goto again;
- }
if (is_hugepd(__hugepd(pmd_val(*pmd))))
err = walk_hugepd_range((hugepd_t *)pmd, addr, next, walk, PMD_SHIFT);
@@ -153,6 +162,10 @@ again:
err = walk_pte_range(pmd, addr, next, walk);
if (err)
break;
+
+ if (walk->action == ACTION_AGAIN)
+ goto again;
+
} while (pmd++, addr = next, addr != end);
return err;