From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D84D68BFC for ; Thu, 11 Jul 2024 21:22:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720732939; cv=none; b=dqG6s0CcFjOHgary/8cz/IT4VBvbBQYDKN+LaYRHN2nIVcInI/ug57bPzMtnUjJ+1Hs2jN0xuPp5E4UCce9FiyWPGnimtS1J4OPd/gPL75pgKUJgaXWtHx9mrBmh9H8uaZR3WodVnAkFA8ZCwddwdsRJi83HnJbm3zw/lyatnTQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720732939; c=relaxed/simple; bh=/mbJ+XRONhT7IsDgSCXno0F6qXvQkSst1AklRybqCpc=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=KGHDMZ5ghdfThsTbzTLKokKYEYuCR0U+Oiq7lVPnf/0eHtxO/6LqfzHI/Ter7+mepWhvzJSTt13YIUNmU66WGWrqQ/qbKn08lnDJCsugdcmoDAPCTl9b44gICf+B3IA4JEXnwsHocIUuPeGEc2cBr42nRUZj9+CyJFPxLFGEs3Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=2Axne4Hi; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="2Axne4Hi" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F0B24C116B1; Thu, 11 Jul 2024 21:22:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1720732939; bh=/mbJ+XRONhT7IsDgSCXno0F6qXvQkSst1AklRybqCpc=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=2Axne4Higf0e5oaGs16W1MWLjsHliczx94EyuzlopmRuR4GNroE40Fe/leNt32sQI XQ5+AAi5W97H1FlEBbOtUnWsVe1omKxakNtH/oWWl/NQkwn/mAqGWkV6LYOdDxW4a7 J3RzJRo860mSG0KlyWqAOZY/ERBtnEIABDdQSGb4= Date: Thu, 11 Jul 2024 14:22:18 -0700 From: Andrew Morton To: Pei Li Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, skhan@linuxfoundation.org, syzkaller-bugs@googlegroups.com, linux-kernel-mentees@lists.linuxfoundation.org, syzbot+35a4414f6e247f515443@syzkaller.appspotmail.com, David Hildenbrand Subject: Re: [PATCH] mm: Fix mmap_assert_locked() in follow_pte() Message-Id: <20240711142218.d7a6cec31366044cbb96a312@linux-foundation.org> In-Reply-To: <20240710-bug12-v1-1-0e5440f9b8d3@gmail.com> References: <20240710-bug12-v1-1-0e5440f9b8d3@gmail.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Wed, 10 Jul 2024 22:13:17 -0700 Pei Li wrote: > This patch fixes this warning by acquiring read lock before entering > untrack_pfn() while write lock is not held. > > syzbot has tested the proposed patch and the reproducer did not > trigger any issue. > Thanks. > --- > Syzbot reported the following warning in follow_pte(): > > WARNING: CPU: 3 PID: 5192 at include/linux/rwsem.h:195 rwsem_assert_held include/linux/rwsem.h:195 [inline] > WARNING: CPU: 3 PID: 5192 at include/linux/rwsem.h:195 mmap_assert_locked include/linux/mmap_lock.h:65 [inline] > WARNING: CPU: 3 PID: 5192 at include/linux/rwsem.h:195 follow_pte+0x414/0x4c0 mm/memory.c:5980 > > This is because we are assuming that mm->mmap_lock should be held when > entering follow_pte(). This is added in commit c5541ba378e3 (mm: > follow_pte() improvements). > > However, in the following call stack, we are not acquring the lock: > follow_phys arch/x86/mm/pat/memtype.c:957 [inline] > get_pat_info+0xf2/0x510 arch/x86/mm/pat/memtype.c:991 > untrack_pfn+0xf7/0x4d0 arch/x86/mm/pat/memtype.c:1104 > unmap_single_vma+0x1bd/0x2b0 mm/memory.c:1819 > zap_page_range_single+0x326/0x560 mm/memory.c:1920 > > In zap_page_range_single(), we passed mm_wr_locked as false, as we do > not expect write lock to be held. > In the special case where vma->vm_flags is set as VM_PFNMAP, we are > hitting untrack_pfn() which eventually calls into follow_phys. I included the above (very relevant) info in the changelog. And I added Fixes: c5541ba378e3 ("mm: follow_pte() improvements") and queued the patch for 6.10-rc7. Hopefully David can review it for us.