The patch below does not apply to the 6.12-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-6.12.y git checkout FETCH_HEAD git cherry-pick -x 927e926d72d9155fde3264459fe9bfd7b5e40d28 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025030948-playhouse-strongman-c9c3@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 927e926d72d9155fde3264459fe9bfd7b5e40d28 Mon Sep 17 00:00:00 2001 From: Suren Baghdasaryan surenb@google.com Date: Wed, 26 Feb 2025 10:55:09 -0800 Subject: [PATCH] userfaultfd: fix PTE unmapping stack-allocated PTE copies
Current implementation of move_pages_pte() copies source and destination PTEs in order to detect concurrent changes to PTEs involved in the move. However these copies are also used to unmap the PTEs, which will fail if CONFIG_HIGHPTE is enabled because the copies are allocated on the stack. Fix this by using the actual PTEs which were kmap()ed.
Link: https://lkml.kernel.org/r/20250226185510.2732648-3-surenb@google.com Fixes: adef440691ba ("userfaultfd: UFFDIO_MOVE uABI") Signed-off-by: Suren Baghdasaryan surenb@google.com Reported-by: Peter Xu peterx@redhat.com Reviewed-by: Peter Xu peterx@redhat.com Cc: Andrea Arcangeli aarcange@redhat.com Cc: Barry Song 21cnbao@gmail.com Cc: Barry Song v-songbaohua@oppo.com Cc: David Hildenbrand david@redhat.com Cc: Hugh Dickins hughd@google.com Cc: Jann Horn jannh@google.com Cc: Kalesh Singh kaleshsingh@google.com Cc: Liam R. Howlett Liam.Howlett@Oracle.com Cc: Lokesh Gidra lokeshgidra@google.com Cc: Lorenzo Stoakes lorenzo.stoakes@oracle.com Cc: Matthew Wilcow (Oracle) willy@infradead.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index f5c6b3454f76..d06453fa8aba 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -1290,8 +1290,8 @@ static int move_pages_pte(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, spin_unlock(src_ptl);
if (!locked) { - pte_unmap(&orig_src_pte); - pte_unmap(&orig_dst_pte); + pte_unmap(src_pte); + pte_unmap(dst_pte); src_pte = dst_pte = NULL; /* now we can block and wait */ folio_lock(src_folio); @@ -1307,8 +1307,8 @@ static int move_pages_pte(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, /* at this point we have src_folio locked */ if (folio_test_large(src_folio)) { /* split_folio() can block */ - pte_unmap(&orig_src_pte); - pte_unmap(&orig_dst_pte); + pte_unmap(src_pte); + pte_unmap(dst_pte); src_pte = dst_pte = NULL; err = split_folio(src_folio); if (err) @@ -1333,8 +1333,8 @@ static int move_pages_pte(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, goto out; } if (!anon_vma_trylock_write(src_anon_vma)) { - pte_unmap(&orig_src_pte); - pte_unmap(&orig_dst_pte); + pte_unmap(src_pte); + pte_unmap(dst_pte); src_pte = dst_pte = NULL; /* now we can block and wait */ anon_vma_lock_write(src_anon_vma); @@ -1352,8 +1352,8 @@ static int move_pages_pte(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, entry = pte_to_swp_entry(orig_src_pte); if (non_swap_entry(entry)) { if (is_migration_entry(entry)) { - pte_unmap(&orig_src_pte); - pte_unmap(&orig_dst_pte); + pte_unmap(src_pte); + pte_unmap(dst_pte); src_pte = dst_pte = NULL; migration_entry_wait(mm, src_pmd, src_addr); err = -EAGAIN; @@ -1396,8 +1396,8 @@ static int move_pages_pte(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, src_folio = folio; src_folio_pte = orig_src_pte; if (!folio_trylock(src_folio)) { - pte_unmap(&orig_src_pte); - pte_unmap(&orig_dst_pte); + pte_unmap(src_pte); + pte_unmap(dst_pte); src_pte = dst_pte = NULL; put_swap_device(si); si = NULL;