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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Jul 07, 2026 at 06:45:09AM -0700, Usama Arif wrote: > madvise_free_pte_range() checks pmd_trans_huge(*pmd) unlocked, then > madvise_free_huge_pmd() takes pmd_trans_huge_lock(). > pmd_is_huge() returns true for a device-private PMD, so orig_pmd can > be device-private and hit the VM_BUG_ON() on the !pmd_present() branch. > > Potential trigger: an HMM-based GPU driver races with madvise(MADV_FREE): > migrate_vma_pages() flips the PMD to a device-private entry between the > caller's pmd_trans_huge() check and the callee's pmd_trans_huge_lock(). > > Skip device-private PMDs after taking the lock, before the > !pmd_present() check. > > Fixes: 368076f52ebe ("mm/huge_memory: add device-private THP support to PMD operations") > Signed-off-by: Usama Arif > --- > mm/huge_memory.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index c0892cc533a9..cfce9f31b30e 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -2296,6 +2296,9 @@ bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, > if (is_huge_zero_pmd(orig_pmd)) > goto out; > > + if (pmd_is_device_private_entry(orig_pmd)) > + goto out; > + > if (unlikely(!pmd_present(orig_pmd))) { > VM_BUG_ON(thp_migration_supported() && > !pmd_is_migration_entry(orig_pmd)); > The change makes sense, I spent some time thinking if we should make madvise pmd free work for THP PMD entries, but that should be a separate patchset, it is much more complex and involved. Reviewed-by: Balbir Singh