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Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kees Cook , Peter Zijlstra , Jann Horn , Pedro Falcato , Hugh Dickins , Pasha Tatashin , Pratyush Yadav , "Matthew Wilcox (Oracle)" , Jan Kara , Zi Yan , Lance Yang , Rik van Riel , Harry Yoo , Alistair Popple , Nico Pache , Ryan Roberts , Dev Jain , Usama Arif , Kiryl Shutsemau , Matthew Brost , John Hubbard , Peter Xu , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Oscar Salvador , Minchan Kim , Muchun Song , Xu Xin , Chengming Zhou , Chris Li , Kemeng Shi , Nhat Pham , Youngjun Park , Gregory Price , Joshua Hahn , Rakie Kim , Ying Huang , Jason Gunthorpe Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-cxl@vger.kernel.org, stable@vger.kernel.org, "David Hildenbrand (Arm)" X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2335; i=david@kernel.org; h=from:subject:message-id; bh=XqIc47B98euy1xZsTgJLG+HPEvLDbYPwpls8mFrjLko=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLLu35/+nuloHL+i7Gzt5riT7MeNJr+acemve9vTq+v+d W3MX695oaOUhUGMg0FWTJElKPi+wcuX62qr3fiYYeawMoEMYeDiFICJiL1lZPisIqzaaFonkqp7 puGr1eKbr55WXg5cXsKUG9A9pzZ8/RqG/66nHXc6y3b+luLN7V/qYqv/hLN04okSz31TJcxn27v MYwMA X-Developer-Key: i=david@kernel.org; a=openpgp; fpr=1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: E8A5CA0003 X-Spam-Status: No, score=-19.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=4.0.1 X-Stat-Signature: dmsjczu7fpbfnw6hzjfks9tk8qsytijk X-HE-Tag: 1793057237-971460 X-HE-Meta: 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 0FqF7Rib BjjeMD9G+v0ALfTrqjE6V3xEnw7VL7QKTXWoDerpVV7aVaayDvixB5xS7My/D08XO/yCnH481Uu3+ZyOiiOUyHS2HDwSW+AExqoI+AiYZ4qXDVgIdWDoz7LRL1Q1/wQjFLpnLJQpMQL3bR2JBVZWDP+cMbL1/8oyx0oVyHngBIZSVkUDdv/4rtL0AABjvIC6ilPIxl6a/DVbVTuxAB1gZxKmms4lvf+m9t3NAH6P+y+P7SGOgXOSlewBQ5M5o1WvpsopyRQwxTa6+9p2ctQ7tTufV0hS21PNGpBg8BB2KHdkQoEOv4wV8kZH64SY7AOThE7+L Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 Once get_old_pud() is fixed to accept PUD leaves, unmap_mapping_range() can clear a leaf between the lookup and the move. Holding mmap_lock in write mode does not prevent this. If the zap happens before move_page_tables() tests the entry, an empty PUD can reach move_normal_pud(), where pud_populate() turns it into a present page table entry. If it happens after the test, move_huge_pud() can instead try to move an empty entry, triggering CONFIG_DEBUG_VM warnings on powerpc. Recheck the source under the page table lock in both helpers. Treat an empty source in move_normal_pud() as a completed move, and use __pud_trans_huge_lock() in move_huge_pud(). In the future we should likely have the code lookup a PUD/PMD lockless once, instead of multiple times, because one of the problematic bits here is the: pud_trans_huge(*old_pud) Fixes: 0881ace292b6 ("mm/mremap: use pmd/pud_poplulate to update page table entries") Cc: stable@vger.kernel.org Reviewed-by: Lorenzo Stoakes (ARM) Signed-off-by: David Hildenbrand (Arm) --- mm/mremap.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/mm/mremap.c b/mm/mremap.c index 16e736c72d9cb..91f0865f6aeea 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -461,14 +461,18 @@ static bool move_normal_pud(struct pagetable_move_control *pmc, if (new_ptl != old_ptl) spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); - /* Clear the pud */ pud = *old_pud; + if (unlikely(pud_none(pud))) + goto out_unlock; + + /* Clear the pud */ pud_clear(old_pud); VM_BUG_ON(!pud_none(*new_pud)); pud_populate(mm, new_pud, pud_pgtable(pud)); flush_tlb_range(vma, pmc->old_addr, pmc->old_addr + PUD_SIZE); +out_unlock: if (new_ptl != old_ptl) spin_unlock(new_ptl); spin_unlock(old_ptl); @@ -503,7 +507,9 @@ static bool move_huge_pud(struct pagetable_move_control *pmc, * We don't have to worry about the ordering of src and dst * ptlocks because exclusive mmap_lock prevents deadlock. */ - old_ptl = pud_lock(mm, old_pud); + old_ptl = __pud_trans_huge_lock(old_pud, vma); + if (unlikely(!old_ptl)) + return false; new_ptl = pud_lockptr(mm, new_pud); if (new_ptl != old_ptl) spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); -- 2.43.0