From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pg1-f202.google.com (mail-pg1-f202.google.com [209.85.215.202]) (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 539AB28FD for ; Wed, 6 Aug 2025 22:00:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.202 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754517627; cv=none; b=nkTI7zmUDejYQxdkdPWuFLKMulvLG+4W2zppAhrdWFEIGW0mkXc3OJAWLxNqPNkdoHJF864RWiwx1QMJH5P4AbJVCRIoaAAxhgBTSnZMMRifVZFvcf88nnrwdewgLv71yiu9Fgy+GQabhdeBDnxz/TwBse+u9QjLW9cKt7Uwe6Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754517627; c=relaxed/simple; bh=5lOaVPIox90EtPwO5fOrQolK9YVZjng1IH3ugUBN0Nw=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=fFqrlJgzmi9Uviy0kzIFKOcJpZQ1wmuc4vWbv9wIMtbwh7C3fJoTLMosUniFA9AG+uueiW0D3kOUbZNl09sadfehd3VT+u4rCWCZ0ULY6nXwrVyGXci+g2daPTMD1822JBtVNRBRFrGIFHEofXQJuKcbSy9o/7q783U0rDI1/AE= 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=h4/y6t/s; arc=none smtp.client-ip=209.85.215.202 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="h4/y6t/s" Received: by mail-pg1-f202.google.com with SMTP id 41be03b00d2f7-b2c00e965d0so184814a12.2 for ; Wed, 06 Aug 2025 15:00:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1754517625; x=1755122425; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=0DGq3Zp4fJ6DZNHeIX2b5x/XDF+UYujZX+55RuFP5IM=; b=h4/y6t/skR7JP+Cp9WK/W7dx276vx6bPQvD4bSWg8UwTfwKsnZFu+PVcmH1Z7h+miB MoIZz6gXvYESgR0G+WZ3tGWhjUJPHE1tCsSpmy5YDRKRQzqUOQ6jabsgcpHU33mY/OPm 0ZfGku4CQSRDHyN5Vsk9gQnY8dxS0w/oduiuKrk/VjR0ARzgHNtZdyTiRV5FEy8LCB6x zqBMj+j+ypGPjehE0SvUITJTiG8UDqCTKr49n3xNiC22n14AkH17xBdETk5aBI9MytSz MN1qQgKkzmDQeE3ojMlnTkC1nbl1l3PNidWv8fZQQ3HvEWkw7SxcENExvYvHXAvOeGfA yelg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1754517625; x=1755122425; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=0DGq3Zp4fJ6DZNHeIX2b5x/XDF+UYujZX+55RuFP5IM=; b=UNppodVg4Y+TF0jpQur08ZXuP5ZckpZvPZB5k5i69Mo2MwjphJ2+nyPdtvjUomgrsG JWml73tYLl6BCcYEk906SzwwqYfja6ZzvVq48AfisYYRnqsbszruwMPMoLus7EgPhOka Mai9DeCjTn6aH7JH3IYccTGV2Qm7ogN4lpSejG+A9zKx4Rqj54eqwPF0eYXlOjoapFn0 FeGUbgOJmgeYt/ujpWFV1mg0SAlEQ0o/ZjXpKrwDjdJ8qkYzip/t3MBWPyG4hE6DD80G 6OIuX2YaCwgt3DET2L+7gRAY+HMXTZUof/aZe8zWNOLWfbwCkPBjEP5JXv9bdy2P3F1R vSvw== X-Forwarded-Encrypted: i=1; AJvYcCVZtF3qu0Xld9cwbGwLZs1biuFzz6yivDFF8xCm0flESJvIC0akVtmK5wb6NUpNxaphX0yPSgusvylecZw=@vger.kernel.org X-Gm-Message-State: AOJu0YwrGtXNxQoZFF/fC9CECIXsbLy2imx3k6QlKeh6TCLv8xjb2ale nuelKjHbafY+ZkzlwKaKh2AgAq6msJN1P/VpE4hZlk8Je/kYvsCn20uUz2+R0YopLJ73W6wxB9t wCwI0Eg== X-Google-Smtp-Source: AGHT+IEgXVgvOPOZLzpUU0uxEIMp34b7pNlfgpNcH4fA0yFqf6+H+2ZoRWuQLabxen09rQvlDcn4hw3n9b0= X-Received: from pjob20.prod.google.com ([2002:a17:90a:8c94:b0:31f:a0:fad4]) (user=surenb job=prod-delivery.src-stubby-dispatcher) by 2002:a17:902:f54b:b0:240:8f4:b36e with SMTP id d9443c01a7336-2429f30a072mr61870205ad.34.1754517625374; Wed, 06 Aug 2025 15:00:25 -0700 (PDT) Date: Wed, 6 Aug 2025 15:00:22 -0700 Precedence: bulk X-Mailing-List: linux-kernel@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: <20250806220022.926763-1-surenb@google.com> Subject: [PATCH v4 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. 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 --- Changes since v3 [1] - Updated the title and changelog, per Peter Xu - Added Reviewed-by: per Peter Xu [1] https://lore.kernel.org/all/20250806154015.769024-1-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