The patch below does not apply to the 6.1-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y git checkout FETCH_HEAD git cherry-pick -x b76b46902c2d0395488c8412e1116c2486cdfcb2 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2024042948-overstuff-untwist-805f@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

b76b46902c2d ("mm/hugetlb: fix missing hugetlb_lock for resv uncharge") d4ab0316cc33 ("mm/hugetlb_cgroup: convert hugetlb_cgroup_uncharge_page() to folios") 0356c4b96f68 ("mm/hugetlb: convert free_huge_page to folios")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From b76b46902c2d0395488c8412e1116c2486cdfcb2 Mon Sep 17 00:00:00 2001 From: Peter Xu peterx@redhat.com Date: Wed, 17 Apr 2024 17:18:35 -0400 Subject: [PATCH] mm/hugetlb: fix missing hugetlb_lock for resv uncharge

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 Reviewed-by: 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

diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 31d00eee028f..53e0ab5c0845 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -3268,9 +3268,12 @@ struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma,

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)