The patch titled Subject: mm/hugetlb: fix missing hugetlb_lock for resv uncharge has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-hugetlb-fix-missing-hugetlb_lock-for-resv-uncharge.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: Peter Xu peterx@redhat.com Subject: mm/hugetlb: fix missing hugetlb_lock for resv uncharge Date: Wed, 17 Apr 2024 17:18:35 -0400

There is a recent report on UFFDIO_COPY over hugetlb:

https://lore.kernel.org/all/000000000000ee06de0616177560@google.com/

350: lockdep_assert_held(&hugetlb_lock);

Should be an issue in hugetlb but triggered in an userfault context, where it goes into the unlikely path where two threads modifying the resv map together. Mike has a fix in that path for resv uncharge but it looks like the locking criteria was overlooked: hugetlb_cgroup_uncharge_folio_rsvd() will update the cgroup pointer, so it requires to be called with the lock held.

Link: https://lkml.kernel.org/r/20240417211836.2742593-3-peterx@redhat.com Fixes: 79aa925bf239 ("hugetlb_cgroup: fix reservation accounting") Signed-off-by: Peter Xu peterx@redhat.com Reported-by: syzbot+4b8077a5fccc61c385a1@syzkaller.appspotmail.com Cc: Mina Almasry almasrymina@google.com Cc: David Hildenbrand david@redhat.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/hugetlb.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/mm/hugetlb.c~mm-hugetlb-fix-missing-hugetlb_lock-for-resv-uncharge +++ a/mm/hugetlb.c @@ -3268,9 +3268,12 @@ struct folio *alloc_hugetlb_folio(struct

rsv_adjust = hugepage_subpool_put_pages(spool, 1); hugetlb_acct_memory(h, -rsv_adjust); - if (deferred_reserve) + if (deferred_reserve) { + spin_lock_irq(&hugetlb_lock); hugetlb_cgroup_uncharge_folio_rsvd(hstate_index(h), pages_per_huge_page(h), folio); + spin_unlock_irq(&hugetlb_lock); + } }

if (!memcg_charge_ret) _

Patches currently in -mm which might be from peterx@redhat.com are

mm-hugetlb-fix-missing-hugetlb_lock-for-resv-uncharge.patch mm-hmm-process-pud-swap-entry-without-pud_huge.patch mm-gup-cache-p4d-in-follow_p4d_mask.patch mm-gup-check-p4d-presence-before-going-on.patch mm-x86-change-pxd_huge-behavior-to-exclude-swap-entries.patch mm-sparc-change-pxd_huge-behavior-to-exclude-swap-entries.patch mm-arm-use-macros-to-define-pmd-pud-helpers.patch mm-arm-redefine-pmd_huge-with-pmd_leaf.patch mm-arm64-merge-pxd_huge-and-pxd_leaf-definitions.patch mm-powerpc-redefine-pxd_huge-with-pxd_leaf.patch mm-gup-merge-pxd-huge-mapping-checks.patch mm-treewide-replace-pxd_huge-with-pxd_leaf.patch mm-treewide-remove-pxd_huge.patch mm-arm-remove-pmd_thp_or_huge.patch mm-document-pxd_leaf-api.patch mm-always-initialise-folio-_deferred_list-fix.patch selftests-mm-run_vmtestssh-fix-hugetlb-mem-size-calculation.patch selftests-mm-run_vmtestssh-fix-hugetlb-mem-size-calculation-fix.patch mm-kconfig-config_pgtable_has_huge_leaves.patch mm-hugetlb-declare-hugetlbfs_pagecache_present-non-static.patch mm-make-hpage_pxd_-macros-even-if-thp.patch mm-introduce-vma_pgtable_walk_beginend.patch mm-arch-provide-pud_pfn-fallback.patch mm-arch-provide-pud_pfn-fallback-fix.patch mm-gup-drop-folio_fast_pin_allowed-in-hugepd-processing.patch mm-gup-refactor-record_subpages-to-find-1st-small-page.patch mm-gup-handle-hugetlb-for-no_page_table.patch mm-gup-cache-pudp-in-follow_pud_mask.patch mm-gup-handle-huge-pud-for-follow_pud_mask.patch mm-gup-handle-huge-pmd-for-follow_pmd_mask.patch mm-gup-handle-huge-pmd-for-follow_pmd_mask-fix.patch mm-gup-handle-hugepd-for-follow_page.patch mm-gup-handle-hugetlb-in-the-generic-follow_page_mask-code.patch mm-allow-anon-exclusive-check-over-hugetlb-tail-pages.patch