From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 822B467E8D for ; Fri, 1 Mar 2024 06:52:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709275969; cv=none; b=OY4VB+RoYKvsCdPaWhWyTDh/B9dlz/BHD0rtauE+NIvpcnAKFrxQGHs5eN9ZiM2acRf95ODNDo8S2YqJac9Fzn2wZoCu25O8rnKJ9GtGx+h4C/Zc3qXH5Ut/pAEcXAorlnHGU+g0Cv5iWS0862v84RJzwoaBbM8fMkscyN9ehAQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709275969; c=relaxed/simple; bh=EwMO3/EgEVBjGx7Oi/1TMd1aSd3iDTtp5SMubZS0FK8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=qMEBUv9hU7hcnnXRjoroozBlBxiIiOds9Y++hDHAxlsBUDHlgx7EBsJqIllZsqKU8eTchJP9cnYTe3dGL1wdoLSvuTE60bnZ7KXSCaBIm/xkRL+cdfY4iUmsac+lyDyOMpKKeXc9luLqi97hLyPPG9pPulYwpVVCDqKa/BmwbEs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=TpxgFeRR; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="TpxgFeRR" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1709275966; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=1hAv7LCsa3iLqGJhJsJviM4n+BZxClj9lSP/nAIPeEE=; b=TpxgFeRROhm2wlLg6Zl15ci8559vraus+YUL3T8KqPMOdgUX0VpfdEi0RF1WE+gx5f+Hst uXv1KW9AuwLE/io6SwGhDDgRVVbyeR74SlrWMUjojhnof0m8jm9BcDCM7YMdg5fTm9J9vA Yz9y80CCmDE7AnpW1M3J9JvHlRAIJdc= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-223-k9AfNMFUM463nT0FJ3bfzg-1; Fri, 01 Mar 2024 01:52:44 -0500 X-MC-Unique: k9AfNMFUM463nT0FJ3bfzg-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 2B95183FC6C; Fri, 1 Mar 2024 06:52:44 +0000 (UTC) Received: from localhost (unknown [10.72.116.6]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 7D4C21BDB1; Fri, 1 Mar 2024 06:52:42 +0000 (UTC) Date: Fri, 1 Mar 2024 14:52:34 +0800 From: Baoquan He To: "yang.zhang" , akpm@linux-foundation.org Cc: ebiederm@xmission.com, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, "yang.zhang" Subject: Re: [PATCH V3] kexec: copy only happens before uchunk goes to zero Message-ID: References: <20240222092119.5602-1-gaoshanliukou@163.com> 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-Disposition: inline In-Reply-To: <20240222092119.5602-1-gaoshanliukou@163.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.5 CC Andrew On 02/22/24 at 05:21pm, yang.zhang wrote: > From: "yang.zhang" > > When loading segments, ubytes is <= mbytes. When ubytes is exhausted, > there could be remaining mbytes. Then in the while loop, the buf pointer > advancing with mchunk will causing meaningless reading even though it > doesn't harm. > > So let's change to make sure that all of the copying and the rest only > happens before uchunk goes to zero. > > Acked-by: Baoquan He > Signed-off-by: yang.zhang > > --- > V2 -> V3: > - Add more detailed description in the commit message > v1 -> v2: > - Only copy before uchunk goes to zero > > V1: https://lore.kernel.org/lkml/20240130101802.23850-1-gaoshanliukou@163.com/ > --- > kernel/kexec_core.c | 44 ++++++++++++++++++++++++-------------------- > 1 file changed, 24 insertions(+), 20 deletions(-) > > diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c > index d08fc7b5db97..2fc3d0e3715a 100644 > --- a/kernel/kexec_core.c > +++ b/kernel/kexec_core.c > @@ -800,22 +800,24 @@ static int kimage_load_normal_segment(struct kimage *image, > PAGE_SIZE - (maddr & ~PAGE_MASK)); > uchunk = min(ubytes, mchunk); > > - /* For file based kexec, source pages are in kernel memory */ > - if (image->file_mode) > - memcpy(ptr, kbuf, uchunk); > - else > - result = copy_from_user(ptr, buf, uchunk); > + if (uchunk) { > + /* For file based kexec, source pages are in kernel memory */ > + if (image->file_mode) > + memcpy(ptr, kbuf, uchunk); > + else > + result = copy_from_user(ptr, buf, uchunk); > + ubytes -= uchunk; > + if (image->file_mode) > + kbuf += uchunk; > + else > + buf += uchunk; > + } > kunmap_local(ptr); > if (result) { > result = -EFAULT; > goto out; > } > - ubytes -= uchunk; > maddr += mchunk; > - if (image->file_mode) > - kbuf += mchunk; > - else > - buf += mchunk; > mbytes -= mchunk; > > cond_resched(); > @@ -866,11 +868,18 @@ static int kimage_load_crash_segment(struct kimage *image, > memset(ptr + uchunk, 0, mchunk - uchunk); > } > > - /* For file based kexec, source pages are in kernel memory */ > - if (image->file_mode) > - memcpy(ptr, kbuf, uchunk); > - else > - result = copy_from_user(ptr, buf, uchunk); > + if (uchunk) { > + /* For file based kexec, source pages are in kernel memory */ > + if (image->file_mode) > + memcpy(ptr, kbuf, uchunk); > + else > + result = copy_from_user(ptr, buf, uchunk); > + ubytes -= uchunk; > + if (image->file_mode) > + kbuf += uchunk; > + else > + buf += uchunk; > + } > kexec_flush_icache_page(page); > kunmap_local(ptr); > arch_kexec_pre_free_pages(page_address(page), 1); > @@ -878,12 +887,7 @@ static int kimage_load_crash_segment(struct kimage *image, > result = -EFAULT; > goto out; > } > - ubytes -= uchunk; > maddr += mchunk; > - if (image->file_mode) > - kbuf += mchunk; > - else > - buf += mchunk; > mbytes -= mchunk; > > cond_resched(); > -- > 2.25.1 >