From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f201.google.com (mail-pf1-f201.google.com [209.85.210.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 670074438B for ; Thu, 7 Aug 2025 20:04:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754597063; cv=none; b=J9vRJd/Oo6k2XeeSsSaSGlbNlDqee5Pvh6NKuLD2F/bqlkivB/mw83wKXVRhs3ecSaqC44Cz1bki10Pk6dudk9vDRTDof8QPLtWONospYRXCybSpgOddAABRnC9tVa+fPrMk4FqEdgL4MTF8uvROWLn7IrHXA5m4g7m5leeNKGY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754597063; c=relaxed/simple; bh=yAdVlTNcDD9pFesPs0syjVkGybrtiBA8rVOi7e+fVgU=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=GNyywv/e4PspD0d0UBGbozwMo6Wxlh2gwHu2pzWg9hXjXf6IJ5I6BKelgZSo+TAY39ypYJ8Vp1E1e83L6hUUFt6iXIoT1GsdDOOuDh+88Asns+gET4Pq0uiigqvqd4tDrkN8H5ipKYbNM8P6P7Mrdhq+5jXWl+5941/tk/rg4lc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--surenb.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=mc66A36I; arc=none smtp.client-ip=209.85.210.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--surenb.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="mc66A36I" Received: by mail-pf1-f201.google.com with SMTP id d2e1a72fcca58-76be4422a36so1989510b3a.0 for ; Thu, 07 Aug 2025 13:04:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1754597062; x=1755201862; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=LopBZLPomTxRQOxqmq+ignoUy2OT7BDqSe/zG/uSirI=; b=mc66A36I2r0ssqiwNNIdYzFzNVd4SVb6T/iiIBp6uOzO8gcbPuR26k64+cbzykoGrg ewA2mmEV5YC9OMgZigMUpLYjW0PBntStO8oQwBTs3SU2AMGmdUiF5Tplq34y5Aw+ZV5W Wzas7LMdtsKYRaDFxs82Z9MY53hCRkv73Mduwvsl0rIw9I4NovhueiYqTa4XKcbEaiDW cK23kdJoGVMfntk+yT92ytt8yB0tJdtOMDPDVEYANk2X5duTfoQWmLjb3ozaVsey2xKA 79sR5qjx25kVVnTJMzciKAyij9qreFlTlSUoNJvC+IPDqrH0eQIvItuTHrVbmxn4YYFZ lv0g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1754597062; x=1755201862; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=LopBZLPomTxRQOxqmq+ignoUy2OT7BDqSe/zG/uSirI=; b=v9AHLw0OnNvtFsbj/4DbJ6CxbLpxNRsTjKHl2TbjZXZnA252RTiwpDfNtYBVJJGV4B WUP4a8gkEdDYTcHFU2OgFYCtEM5djZ/xnu2QPKP7eAZY2OvUWv/xp28LBbdqWMcG1kvW UePaaH/GTSVf1sOvnPfRlxLMpFmHB7/KvAJEbC/PT2wsTu4wB1g0fn0I3zyJpRm2ivrm xBGa3UpOkB9W4xo9wndrea/7fqP4nUiKd8RNgB422YWk4BSuhxDhniMUsMQ6bgaMH7JL nAkScnNviJktLx6tfR7ATKB6nSU+oM8boa1xR3O31sjSFJbZbLZv66xlNoZN8sSsv+r7 WGGw== X-Forwarded-Encrypted: i=1; AJvYcCWyn8vYfrLKVUcK3KyXRCpA7VUyQi8pZUtjj8wMWkEN6ufJxUJn/yZkdMGEAnEow+1EY7K2L38=@vger.kernel.org X-Gm-Message-State: AOJu0YwQoacrjHlHExpbSO+mYrd2B96KOEQd/0dZsUR7WJ3aOkCp/seY 6P0jamvvok+AWnhopASE6ueHKQDyI0KEa5g59P3OJRx/5I8oPlwroHZmlawVeEmpPl0tQNWxIet 3fRojGA== X-Google-Smtp-Source: AGHT+IFfxdE58fnJSmEe7IBG3NEKzHhTu/Wj771qmKF+e/CxQGVaBBcd11vmFgPtdAqEdHyAx5FA9bsYdtI= X-Received: from pfsy42.prod.google.com ([2002:a05:6a00:3aa:b0:76b:dec5:1cb3]) (user=surenb job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a20:a128:b0:23d:e6ec:5410 with SMTP id adf61e73a8af0-240556a77cemr188540637.17.1754597061631; Thu, 07 Aug 2025 13:04:21 -0700 (PDT) Date: Thu, 7 Aug 2025 13:04:18 -0700 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.50.1.703.g449372360f-goog Message-ID: <20250807200418.1963585-1-surenb@google.com> Subject: [PATCH v5 1/1] userfaultfd: fix a crash in UFFDIO_MOVE when PMD is a migration entry From: Suren Baghdasaryan To: akpm@linux-foundation.org Cc: peterx@redhat.com, david@redhat.com, aarcange@redhat.com, lokeshgidra@google.com, surenb@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, syzbot+b446dbe27035ef6bd6c2@syzkaller.appspotmail.com, stable@vger.kernel.org Content-Type: text/plain; charset="UTF-8" When UFFDIO_MOVE encounters a migration PMD entry, it proceeds with obtaining a folio and accessing it even though the entry is swp_entry_t. Add the missing check and let split_huge_pmd() handle migration entries. While at it also remove unnecessary folio check. Fixes: adef440691ba ("userfaultfd: UFFDIO_MOVE uABI") Reported-by: syzbot+b446dbe27035ef6bd6c2@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/68794b5c.a70a0220.693ce.0050.GAE@google.com/ Signed-off-by: Suren Baghdasaryan Reviewed-by: Peter Xu Cc: stable@vger.kernel.org --- Applies to mm-unstable after reverting older v4 [1] version. Changes since v4 [1] - Removed extra folio check, per David Hildenbrand [1] https://lore.kernel.org/all/20250806220022.926763-1-surenb@google.com/ mm/userfaultfd.c | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-) diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 5431c9dd7fd7..aefdf3a812a1 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -1826,13 +1826,16 @@ ssize_t move_pages(struct userfaultfd_ctx *ctx, unsigned long dst_start, /* Check if we can move the pmd without splitting it. */ if (move_splits_huge_pmd(dst_addr, src_addr, src_start + len) || !pmd_none(dst_pmdval)) { - struct folio *folio = pmd_folio(*src_pmd); - - if (!folio || (!is_huge_zero_folio(folio) && - !PageAnonExclusive(&folio->page))) { - spin_unlock(ptl); - err = -EBUSY; - break; + /* Can be a migration entry */ + if (pmd_present(*src_pmd)) { + struct folio *folio = pmd_folio(*src_pmd); + + if (!is_huge_zero_folio(folio) && + !PageAnonExclusive(&folio->page)) { + spin_unlock(ptl); + err = -EBUSY; + break; + } } spin_unlock(ptl); -- 2.50.1.703.g449372360f-goog