Re: [PATCH v2 1/2] secretmem/gup: don't check if page is secretmem without reference
From: David Hildenbrand <hidden>
Date: 2021-04-20 13:20:16
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linux-api, linux-arch, linux-fsdevel, linux-kselftest, linux-mm, linux-riscv, lkml
On 20.04.21 15:16, Mike Rapoport wrote:
quoted hunk ↗ jump to hunk
From: Mike Rapoport <redacted> The check in gup_pte_range() whether a page belongs to a secretmem mapping is performed before grabbing the page reference. To avoid potential race move the check after try_grab_compound_head(). Signed-off-by: Mike Rapoport <redacted> --- mm/gup.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)diff --git a/mm/gup.c b/mm/gup.c index c3a17b189064..4b58c016e949 100644 --- a/mm/gup.c +++ b/mm/gup.c@@ -2080,13 +2080,13 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, VM_BUG_ON(!pfn_valid(pte_pfn(pte))); page = pte_page(pte); - if (page_is_secretmem(page)) - goto pte_unmap; - head = try_grab_compound_head(page, 1, flags); if (!head) goto pte_unmap; + if (page_is_secretmem(page)) + goto pte_unmap; +
Looking at the hunk below, I wonder if you're missing a put_compound_head(). (also, I'd do if unlikely(page_is_secretmem()) but that's a different discussion)
if (unlikely(pte_val(pte) != pte_val(*ptep))) {
put_compound_head(head, 1, flags);
goto pte_unmap;-- Thanks, David / dhildenb _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel