From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f202.google.com (mail-pl1-f202.google.com [209.85.214.202]) (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 583B019A for ; Wed, 6 Aug 2025 15:40:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.202 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754494820; cv=none; b=er/BrR7YwcS5CbjTQHYqW7RUzBkWXSC1R1q3SJHiY9pDcVgCupsopE2NGEjBjqfqM1Pfe+1yN6zmnGF0TKwLkXo86DQwj5kRdMYYus8CN+yWpmjMMa+PNmNF7eoqfa5J/NDiRfXPV5ngwZsGRVGkAQ9D08+3AWUg95fjLDfJk3s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754494820; c=relaxed/simple; bh=YKmeLfJVeftgXNpU/CCjjFjhzT4YXi3X/6DOHGjU/QI=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=to+Nlyw2Paoq1Wj+sCZRNgu5mMoaFw1941TdyJDo5glcJlfSsnOVO1uJ7+9ry6XCBrbPR4XkvmC75ShmsufrIujtKTtLX6ZSFUk1WqXvWpKmV3MZb3IzHLJKyHoyBlWmY/uML0JEMg52pWVyi8IXEeXqzDBllshbpLRFEuJTwDI= 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=0zMuj7od; arc=none smtp.client-ip=209.85.214.202 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="0zMuj7od" Received: by mail-pl1-f202.google.com with SMTP id d9443c01a7336-2400117dd80so48357035ad.2 for ; Wed, 06 Aug 2025 08:40:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1754494819; x=1755099619; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=/rcbJP9GsUTVLgzIeF6EjF73i2MBiTUObyAO9IzHFJw=; b=0zMuj7od9xgDueMQ7xT3ACgyG+ve2iB/nq+gjnhlF9ZcJAWS2oDHdbdvDhzSODyfCM WeQaYN4ycd/9vh4i3Xc4h6GGYwpSoz6qVRS5QVcS3lx6DXxUogt6M4+EuOnvPzcpzojf 1OViMSV96/pSQKRFRtGHObq8wieGk8jIU7XmeN2vdIi34SNQVTC+WQOfPewAfm2JIgxc HQRcyQMzHXFSkqpK9SU7hI0znJM91KMJf/GaW6PMI10rdaSO3NrOwGKxXQ+UB/+T4wH/ hn4WUPxCGR16qZao5hhOBvNazPvTgyitlRmN3KHq1VOY91iMHwABcqW5kj9YONS0OccX nRpg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1754494819; x=1755099619; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=/rcbJP9GsUTVLgzIeF6EjF73i2MBiTUObyAO9IzHFJw=; b=axYvViRwJkNc3sVqV1fyvVFmN41d1Nq1ksi3P6JmNFu0cETkZ5lIsnyJHANRNGRUZe sg6CHp3NPU2GRh97tKwcjfnJbPTvvIUnKtwgUxiE6vCtssLOfv7MpRrj5rrbdK2pl/NE YzlyN6lrZw7SBnK93pgv//u7xEJbBWmIsxG/e40O2zc1Mmpk5WuzKQj6RVUC/W5FT732 nTaqp9NFXZINkVonlbPEoBxFZ4wlBSZBL+f/MP9utyU44KFn+7A3sGjD307ysrO+kTLu P9creo5xnFHqem0fhYRW9Smaioar8+fblPZt30MJ0By7K2LRgbHe2sVUqDdQ47ki12cQ t8bA== X-Forwarded-Encrypted: i=1; AJvYcCVRUN/whYkzOtr0XRwjHCrnhs2UTAIeW8TrWhMU4gP2GfWIALNfYL9Yx6mk6wD+sWo0uxPpB8Q=@vger.kernel.org X-Gm-Message-State: AOJu0Yy4T+584xph9opwSsTNT2ZPeugaiQP9doKNi8EV67LCEHu4A5ia lR1CUk7lfdfFPe1uR8ga+lHESh6iipNdiT1/rcJvJwrlsnVMda6X4K0uJqaPBS6eLjl0ksvjZOF bZqDsKw== X-Google-Smtp-Source: AGHT+IGi3LZt6GUnUZOPcAyMejp52TBB0RjJh6S5HK/q7683T2GfXcCeCP9l0/WWit8jiCrja5/iLHKI5zY= X-Received: from plbko5.prod.google.com ([2002:a17:903:7c5:b0:23f:e9a5:d20a]) (user=surenb job=prod-delivery.src-stubby-dispatcher) by 2002:a17:902:f70e:b0:23f:fa2c:3aff with SMTP id d9443c01a7336-2429f5adf47mr38827855ad.52.1754494818714; Wed, 06 Aug 2025 08:40:18 -0700 (PDT) Date: Wed, 6 Aug 2025 08:40:15 -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 2.50.1.565.gc32cd1483b-goog Message-ID: <20250806154015.769024-1-surenb@google.com> Subject: [PATCH v3 1/1] userfaultfd: fix a crash in UFFDIO_MOVE with some non-present PMDs 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 is used with UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES and it encounters a non-present PMD (migration entry), it proceeds with folio access even though the folio is not present. Add the missing check and let split_huge_pmd() handle migration entries. 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 Cc: stable@vger.kernel.org --- Changes since v2 [1] - Updated the title and changelog, per David Hildenbrand - Removed extra checks for non-present not-migration PMD entries, per Peter Xu [1] https://lore.kernel.org/all/20250731154442.319568-1-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..116481606be8 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 (!folio || (!is_huge_zero_folio(folio) && + !PageAnonExclusive(&folio->page))) { + spin_unlock(ptl); + err = -EBUSY; + break; + } } spin_unlock(ptl); base-commit: 8e7e0c6d09502e44aa7a8fce0821e042a6ec03d1 -- 2.50.1.565.gc32cd1483b-goog