From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 56E8AC433EF for ; Sat, 23 Apr 2022 14:46:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230230AbiDWOtJ (ORCPT ); Sat, 23 Apr 2022 10:49:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54518 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229445AbiDWOtI (ORCPT ); Sat, 23 Apr 2022 10:49:08 -0400 Received: from out30-44.freemail.mail.aliyun.com (out30-44.freemail.mail.aliyun.com [115.124.30.44]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E68C3BC1E; Sat, 23 Apr 2022 07:46:10 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R131e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e01424;MF=xuanzhuo@linux.alibaba.com;NM=1;PH=DS;RN=9;SR=0;TI=SMTPD_---0VAvd12x_1650725167; Received: from localhost(mailfrom:xuanzhuo@linux.alibaba.com fp:SMTPD_---0VAvd12x_1650725167) by smtp.aliyun-inc.com(127.0.0.1); Sat, 23 Apr 2022 22:46:07 +0800 Message-ID: <1650724608.256497-2-xuanzhuo@linux.alibaba.com> Subject: Re: [PATCH net] virtio_net: fix wrong buf address calculation when using xdp Date: Sat, 23 Apr 2022 22:36:48 +0800 From: Xuan Zhuo To: Nikolay Aleksandrov Cc: kuba@kernel.org, davem@davemloft.net, stable@vger.kernel.org, Jason Wang , Daniel Borkmann , "Michael S. Tsirkin" , virtualization@lists.linux-foundation.org, netdev@vger.kernel.org References: <20220423112612.2292774-1-razor@blackwall.org> <1650720683.8168066-1-xuanzhuo@linux.alibaba.com> <8d511a16-8d69-82b1-48a1-24de3a592aef@blackwall.org> In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Sat, 23 Apr 2022 17:30:11 +0300, Nikolay Aleksandrov wrote: > On 23/04/2022 17:16, Nikolay Aleksandrov wrote: > > On 23/04/2022 16:31, Xuan Zhuo wrote: > >> On Sat, 23 Apr 2022 14:26:12 +0300, Nikolay Aleksandrov wrote: > >>> We received a report[1] of kernel crashes when Cilium is used in XDP > >>> mode with virtio_net after updating to newer kernels. After > >>> investigating the reason it turned out that when using mergeable bufs > >>> with an XDP program which adjusts xdp.data or xdp.data_meta page_to_buf() > >>> calculates the build_skb address wrong because the offset can become less > >>> than the headroom so it gets the address of the previous page (-X bytes > >>> depending on how lower offset is): > >>> page_to_skb: page addr ffff9eb2923e2000 buf ffff9eb2923e1ffc offset 252 headroom 256 > >>> > >>> This is a pr_err() I added in the beginning of page_to_skb which clearly > >>> shows offset that is less than headroom by adding 4 bytes of metadata > >>> via an xdp prog. The calculations done are: > >>> receive_mergeable(): > >>> headroom = VIRTIO_XDP_HEADROOM; // VIRTIO_XDP_HEADROOM == 256 bytes > >>> offset = xdp.data - page_address(xdp_page) - > >>> vi->hdr_len - metasize; > >>> > >>> page_to_skb(): > >>> p = page_address(page) + offset; > >>> ... > >>> buf = p - headroom; > >>> > >>> Now buf goes -4 bytes from the page's starting address as can be seen > >>> above which is set as skb->head and skb->data by build_skb later. Depending > >>> on what's done with the skb (when it's freed most often) we get all kinds > >>> of corruptions and BUG_ON() triggers in mm[2]. The story of the faulty > >>> commit is interesting because the patch was sent and applied twice (it > >>> seems the first one got lost during merge back in 5.13 window). The > >>> first version of the patch that was applied as: > >>> commit 7bf64460e3b2 ("virtio-net: get build_skb() buf by data ptr") > >>> was actually correct because it calculated the page starting address > >>> without relying on offset or headroom, but then the second version that > >>> was applied as: > >>> commit 8fb7da9e9907 ("virtio_net: get build_skb() buf by data ptr") > >>> was wrong and added the above calculation. > >>> An example xdp prog[3] is below. > >>> > >>> [1] https://github.com/cilium/cilium/issues/19453 > >>> > >>> [2] Two of the many traces: > >>> [ 40.437400] BUG: Bad page state in process swapper/0 pfn:14940 > >>> [ 40.916726] BUG: Bad page state in process systemd-resolve pfn:053b7 > >>> [ 41.300891] kernel BUG at include/linux/mm.h:720! > >>> [ 41.301801] invalid opcode: 0000 [#1] PREEMPT SMP NOPTI > >>> [ 41.302784] CPU: 1 PID: 1181 Comm: kubelet Kdump: loaded Tainted: G B W 5.18.0-rc1+ #37 > >>> [ 41.304458] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1.fc35 04/01/2014 > >>> [ 41.306018] RIP: 0010:page_frag_free+0x79/0xe0 > >>> [ 41.306836] Code: 00 00 75 ea 48 8b 07 a9 00 00 01 00 74 e0 48 8b 47 48 48 8d 50 ff a8 01 48 0f 45 fa eb d0 48 c7 c6 18 b8 30 a6 e8 d7 f8 fc ff <0f> 0b 48 8d 78 ff eb bc 48 8b 07 a9 00 00 01 00 74 3a 66 90 0f b6 > >>> [ 41.310235] RSP: 0018:ffffac05c2a6bc78 EFLAGS: 00010292 > >>> [ 41.311201] RAX: 000000000000003e RBX: 0000000000000000 RCX: 0000000000000000 > >>> [ 41.312502] RDX: 0000000000000001 RSI: ffffffffa6423004 RDI: 00000000ffffffff > >>> [ 41.313794] RBP: ffff993c98823600 R08: 0000000000000000 R09: 00000000ffffdfff > >>> [ 41.315089] R10: ffffac05c2a6ba68 R11: ffffffffa698ca28 R12: ffff993c98823600 > >>> [ 41.316398] R13: ffff993c86311ebc R14: 0000000000000000 R15: 000000000000005c > >>> [ 41.317700] FS: 00007fe13fc56740(0000) GS:ffff993cdd900000(0000) knlGS:0000000000000000 > >>> [ 41.319150] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > >>> [ 41.320152] CR2: 000000c00008a000 CR3: 0000000014908000 CR4: 0000000000350ee0 > >>> [ 41.321387] Call Trace: > >>> [ 41.321819] > >>> [ 41.322193] skb_release_data+0x13f/0x1c0 > >>> [ 41.322902] __kfree_skb+0x20/0x30 > >>> [ 41.343870] tcp_recvmsg_locked+0x671/0x880 > >>> [ 41.363764] tcp_recvmsg+0x5e/0x1c0 > >>> [ 41.384102] inet_recvmsg+0x42/0x100 > >>> [ 41.406783] ? sock_recvmsg+0x1d/0x70 > >>> [ 41.428201] sock_read_iter+0x84/0xd0 > >>> [ 41.445592] ? 0xffffffffa3000000 > >>> [ 41.462442] new_sync_read+0x148/0x160 > >>> [ 41.479314] ? 0xffffffffa3000000 > >>> [ 41.496937] vfs_read+0x138/0x190 > >>> [ 41.517198] ksys_read+0x87/0xc0 > >>> [ 41.535336] do_syscall_64+0x3b/0x90 > >>> [ 41.551637] entry_SYSCALL_64_after_hwframe+0x44/0xae > >>> [ 41.568050] RIP: 0033:0x48765b > >>> [ 41.583955] Code: e8 4a 35 fe ff eb 88 cc cc cc cc cc cc cc cc e8 fb 7a fe ff 48 8b 7c 24 10 48 8b 74 24 18 48 8b 54 24 20 48 8b 44 24 08 0f 05 <48> 3d 01 f0 ff ff 76 20 48 c7 44 24 28 ff ff ff ff 48 c7 44 24 30 > >>> [ 41.632818] RSP: 002b:000000c000a2f5b8 EFLAGS: 00000212 ORIG_RAX: 0000000000000000 > >>> [ 41.664588] RAX: ffffffffffffffda RBX: 000000c000062000 RCX: 000000000048765b > >>> [ 41.681205] RDX: 0000000000005e54 RSI: 000000c000e66000 RDI: 0000000000000016 > >>> [ 41.697164] RBP: 000000c000a2f608 R08: 0000000000000001 R09: 00000000000001b4 > >>> [ 41.713034] R10: 00000000000000b6 R11: 0000000000000212 R12: 00000000000000e9 > >>> [ 41.728755] R13: 0000000000000001 R14: 000000c000a92000 R15: ffffffffffffffff > >>> [ 41.744254] > >>> [ 41.758585] Modules linked in: br_netfilter bridge veth netconsole virtio_net > >>> > >>> and > >>> > >>> [ 33.524802] BUG: Bad page state in process systemd-network pfn:11e60 > >>> [ 33.528617] page ffffe05dc0147b00 ffffe05dc04e7a00 ffff8ae9851ec000 (1) len 82 offset 252 metasize 4 hroom 0 hdr_len 12 data ffff8ae9851ec10c data_meta ffff8ae9851ec108 data_end ffff8ae9851ec14e > >>> [ 33.529764] page:000000003792b5ba refcount:0 mapcount:-512 mapping:0000000000000000 index:0x0 pfn:0x11e60 > >>> [ 33.532463] flags: 0xfffffc0000000(node=0|zone=1|lastcpupid=0x1fffff) > >>> [ 33.532468] raw: 000fffffc0000000 0000000000000000 dead000000000122 0000000000000000 > >>> [ 33.532470] raw: 0000000000000000 0000000000000000 00000000fffffdff 0000000000000000 > >>> [ 33.532471] page dumped because: nonzero mapcount > >>> [ 33.532472] Modules linked in: br_netfilter bridge veth netconsole virtio_net > >>> [ 33.532479] CPU: 0 PID: 791 Comm: systemd-network Kdump: loaded Not tainted 5.18.0-rc1+ #37 > >>> [ 33.532482] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1.fc35 04/01/2014 > >>> [ 33.532484] Call Trace: > >>> [ 33.532496] > >>> [ 33.532500] dump_stack_lvl+0x45/0x5a > >>> [ 33.532506] bad_page.cold+0x63/0x94 > >>> [ 33.532510] free_pcp_prepare+0x290/0x420 > >>> [ 33.532515] free_unref_page+0x1b/0x100 > >>> [ 33.532518] skb_release_data+0x13f/0x1c0 > >>> [ 33.532524] kfree_skb_reason+0x3e/0xc0 > >>> [ 33.532527] ip6_mc_input+0x23c/0x2b0 > >>> [ 33.532531] ip6_sublist_rcv_finish+0x83/0x90 > >>> [ 33.532534] ip6_sublist_rcv+0x22b/0x2b0 > >>> > >>> [3] XDP program to reproduce(xdp_pass.c): > >>> #include > >>> #include > >>> > >>> SEC("xdp_pass") > >>> int xdp_pkt_pass(struct xdp_md *ctx) > >>> { > >>> bpf_xdp_adjust_head(ctx, -(int)32); > >>> return XDP_PASS; > >>> } > >>> > >>> char _license[] SEC("license") = "GPL"; > >>> > >>> compile: clang -O2 -g -Wall -target bpf -c xdp_pass.c -o xdp_pass.o > >>> load on virtio_net: ip link set enp1s0 xdpdrv obj xdp_pass.o sec xdp_pass > >>> > >>> CC: stable@vger.kernel.org > >>> CC: Jason Wang > >>> CC: Xuan Zhuo > >>> CC: Daniel Borkmann > >>> CC: "Michael S. Tsirkin" > >>> CC: virtualization@lists.linux-foundation.org > >>> Fixes: 8fb7da9e9907 ("virtio_net: get build_skb() buf by data ptr") > >>> Signed-off-by: Nikolay Aleksandrov > >>> --- > >>> drivers/net/virtio_net.c | 8 ++++++-- > >>> 1 file changed, 6 insertions(+), 2 deletions(-) > >>> > >>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > >>> index 87838cbe38cf..0687dd88e97f 100644 > >>> --- a/drivers/net/virtio_net.c > >>> +++ b/drivers/net/virtio_net.c > >>> @@ -434,9 +434,13 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi, > >>> * Buffers with headroom use PAGE_SIZE as alloc size, see > >>> * add_recvbuf_mergeable() + get_mergeable_buf_len() > >>> */ > >>> - truesize = headroom ? PAGE_SIZE : truesize; > >>> + if (headroom) { > >>> + truesize = PAGE_SIZE; > >>> + buf = (char *)((unsigned long)p & PAGE_MASK); > >> > >> The reason for not doing this is that buf and p may not be on the same page, and > >> buf is probably not page-aligned. > >> > >> The implementation of virtio-net merge is add_recvbuf_mergeable(), which > >> allocates a large block of memory at one time, and allocates from it each time. > >> Although in xdp mode, each allocation is page_size, it does not guarantee that > >> each allocation is page-aligned . > >> > >> The problem here is that the value of headroom is wrong, the package is > >> structured like this: > >> > >> from device | headroom | virtio-net hdr | data | > >> after xdp | headroom | virtio-net hdr | meta | data | > > > > You're free to push data back (not necessarily through meta). > > You don't have virtio-net hdr for the xdp case (hdr_valid is false there). > > > >> > >> The page_address(page) + offset we pass to page_to_skb() points to the > >> virtio-net hdr. > >> > >> So I think it might be better to change it this way. > >> > >> Thanks. > >> > >> > >> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > >> index 87838cbe38cf..086ae835ec86 100644 > >> --- a/drivers/net/virtio_net.c > >> +++ b/drivers/net/virtio_net.c > >> @@ -1012,7 +1012,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev, > >> head_skb = page_to_skb(vi, rq, xdp_page, offset, > >> len, PAGE_SIZE, false, > >> metasize, > >> - VIRTIO_XDP_HEADROOM); > >> + VIRTIO_XDP_HEADROOM - metazie); > >> return head_skb; > >> } > >> break; > > > > That patch doesn't fix it, as I said with xdp you can move both data and data_meta. > > So just doing that would take care of the meta, but won't take care of moving data. > > > > Also it doesn't take care of the case where page_to_skb() is called with the original page > i.e. when we already have headroom, so we hit the next/standard page_to_skb() call (xdp_page == page). Yes, you are right. > > The above change guarantees that buf and p will be in the same page How can this be guaranteed? 1. For example, we applied for a 32k buffer first, and took away 1500 + hdr_len from the allocation. 2. set xdp 3. alloc for new buffer The buffer allocated in the third step must be unaligned, and it is entirely possible that p and buf are not on the same page. I fixed my previous patch. Thanks. diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 87838cbe38cf..d95e82255b94 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -1005,6 +1005,8 @@ static struct sk_buff *receive_mergeable(struct net_device *dev, * xdp.data_meta were adjusted */ len = xdp.data_end - xdp.data + vi->hdr_len + metasize; + + headroom = xdp.data - vi->hdr_len - metasize - (buf - headroom); /* We can only create skb based on xdp_page. */ if (unlikely(xdp_page != page)) { rcu_read_unlock(); @@ -1012,7 +1014,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev, head_skb = page_to_skb(vi, rq, xdp_page, offset, len, PAGE_SIZE, false, metasize, - VIRTIO_XDP_HEADROOM); + headroom); return head_skb; } break; From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from smtp4.osuosl.org (smtp4.osuosl.org [140.211.166.137]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 5C6C9C433F5 for ; Sat, 23 Apr 2022 14:46:22 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp4.osuosl.org (Postfix) with ESMTP id EB50B415CE; Sat, 23 Apr 2022 14:46:21 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp4.osuosl.org ([127.0.0.1]) by localhost (smtp4.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id ft9DPUsY5U4Q; Sat, 23 Apr 2022 14:46:20 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [IPv6:2605:bc80:3010:104::8cd3:938]) by smtp4.osuosl.org (Postfix) with ESMTPS id 60DEA415C5; Sat, 23 Apr 2022 14:46:19 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 443F0C0032; Sat, 23 Apr 2022 14:46:19 +0000 (UTC) Received: from smtp3.osuosl.org (smtp3.osuosl.org [IPv6:2605:bc80:3010::136]) by lists.linuxfoundation.org (Postfix) with ESMTP id 4E39EC002D for ; Sat, 23 Apr 2022 14:46:17 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp3.osuosl.org (Postfix) with ESMTP id 3C55260BA8 for ; Sat, 23 Apr 2022 14:46:17 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp3.osuosl.org ([127.0.0.1]) by localhost (smtp3.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id l5dNzUYb1-JD for ; Sat, 23 Apr 2022 14:46:15 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0 Received: from out30-132.freemail.mail.aliyun.com (out30-132.freemail.mail.aliyun.com [115.124.30.132]) by smtp3.osuosl.org (Postfix) with ESMTPS id 4BD1560B44 for ; Sat, 23 Apr 2022 14:46:13 +0000 (UTC) X-Alimail-AntiSpam: AC=PASS; BC=-1|-1; BR=01201311R131e4; CH=green; DM=||false|; DS=||; FP=0|-1|-1|-1|0|-1|-1|-1; HT=e01e01424; MF=xuanzhuo@linux.alibaba.com; NM=1; PH=DS; RN=9; SR=0; TI=SMTPD_---0VAvd12x_1650725167; Received: from localhost(mailfrom:xuanzhuo@linux.alibaba.com fp:SMTPD_---0VAvd12x_1650725167) by smtp.aliyun-inc.com(127.0.0.1); Sat, 23 Apr 2022 22:46:07 +0800 Message-ID: <1650724608.256497-2-xuanzhuo@linux.alibaba.com> Subject: Re: [PATCH net] virtio_net: fix wrong buf address calculation when using xdp Date: Sat, 23 Apr 2022 22:36:48 +0800 From: Xuan Zhuo To: Nikolay Aleksandrov References: <20220423112612.2292774-1-razor@blackwall.org> <1650720683.8168066-1-xuanzhuo@linux.alibaba.com> <8d511a16-8d69-82b1-48a1-24de3a592aef@blackwall.org> In-Reply-To: Cc: Daniel Borkmann , "Michael S. Tsirkin" , netdev@vger.kernel.org, stable@vger.kernel.org, virtualization@lists.linux-foundation.org, kuba@kernel.org, davem@davemloft.net X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" On Sat, 23 Apr 2022 17:30:11 +0300, Nikolay Aleksandrov wrote: > On 23/04/2022 17:16, Nikolay Aleksandrov wrote: > > On 23/04/2022 16:31, Xuan Zhuo wrote: > >> On Sat, 23 Apr 2022 14:26:12 +0300, Nikolay Aleksandrov wrote: > >>> We received a report[1] of kernel crashes when Cilium is used in XDP > >>> mode with virtio_net after updating to newer kernels. After > >>> investigating the reason it turned out that when using mergeable bufs > >>> with an XDP program which adjusts xdp.data or xdp.data_meta page_to_buf() > >>> calculates the build_skb address wrong because the offset can become less > >>> than the headroom so it gets the address of the previous page (-X bytes > >>> depending on how lower offset is): > >>> page_to_skb: page addr ffff9eb2923e2000 buf ffff9eb2923e1ffc offset 252 headroom 256 > >>> > >>> This is a pr_err() I added in the beginning of page_to_skb which clearly > >>> shows offset that is less than headroom by adding 4 bytes of metadata > >>> via an xdp prog. The calculations done are: > >>> receive_mergeable(): > >>> headroom = VIRTIO_XDP_HEADROOM; // VIRTIO_XDP_HEADROOM == 256 bytes > >>> offset = xdp.data - page_address(xdp_page) - > >>> vi->hdr_len - metasize; > >>> > >>> page_to_skb(): > >>> p = page_address(page) + offset; > >>> ... > >>> buf = p - headroom; > >>> > >>> Now buf goes -4 bytes from the page's starting address as can be seen > >>> above which is set as skb->head and skb->data by build_skb later. Depending > >>> on what's done with the skb (when it's freed most often) we get all kinds > >>> of corruptions and BUG_ON() triggers in mm[2]. The story of the faulty > >>> commit is interesting because the patch was sent and applied twice (it > >>> seems the first one got lost during merge back in 5.13 window). The > >>> first version of the patch that was applied as: > >>> commit 7bf64460e3b2 ("virtio-net: get build_skb() buf by data ptr") > >>> was actually correct because it calculated the page starting address > >>> without relying on offset or headroom, but then the second version that > >>> was applied as: > >>> commit 8fb7da9e9907 ("virtio_net: get build_skb() buf by data ptr") > >>> was wrong and added the above calculation. > >>> An example xdp prog[3] is below. > >>> > >>> [1] https://github.com/cilium/cilium/issues/19453 > >>> > >>> [2] Two of the many traces: > >>> [ 40.437400] BUG: Bad page state in process swapper/0 pfn:14940 > >>> [ 40.916726] BUG: Bad page state in process systemd-resolve pfn:053b7 > >>> [ 41.300891] kernel BUG at include/linux/mm.h:720! > >>> [ 41.301801] invalid opcode: 0000 [#1] PREEMPT SMP NOPTI > >>> [ 41.302784] CPU: 1 PID: 1181 Comm: kubelet Kdump: loaded Tainted: G B W 5.18.0-rc1+ #37 > >>> [ 41.304458] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1.fc35 04/01/2014 > >>> [ 41.306018] RIP: 0010:page_frag_free+0x79/0xe0 > >>> [ 41.306836] Code: 00 00 75 ea 48 8b 07 a9 00 00 01 00 74 e0 48 8b 47 48 48 8d 50 ff a8 01 48 0f 45 fa eb d0 48 c7 c6 18 b8 30 a6 e8 d7 f8 fc ff <0f> 0b 48 8d 78 ff eb bc 48 8b 07 a9 00 00 01 00 74 3a 66 90 0f b6 > >>> [ 41.310235] RSP: 0018:ffffac05c2a6bc78 EFLAGS: 00010292 > >>> [ 41.311201] RAX: 000000000000003e RBX: 0000000000000000 RCX: 0000000000000000 > >>> [ 41.312502] RDX: 0000000000000001 RSI: ffffffffa6423004 RDI: 00000000ffffffff > >>> [ 41.313794] RBP: ffff993c98823600 R08: 0000000000000000 R09: 00000000ffffdfff > >>> [ 41.315089] R10: ffffac05c2a6ba68 R11: ffffffffa698ca28 R12: ffff993c98823600 > >>> [ 41.316398] R13: ffff993c86311ebc R14: 0000000000000000 R15: 000000000000005c > >>> [ 41.317700] FS: 00007fe13fc56740(0000) GS:ffff993cdd900000(0000) knlGS:0000000000000000 > >>> [ 41.319150] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > >>> [ 41.320152] CR2: 000000c00008a000 CR3: 0000000014908000 CR4: 0000000000350ee0 > >>> [ 41.321387] Call Trace: > >>> [ 41.321819] > >>> [ 41.322193] skb_release_data+0x13f/0x1c0 > >>> [ 41.322902] __kfree_skb+0x20/0x30 > >>> [ 41.343870] tcp_recvmsg_locked+0x671/0x880 > >>> [ 41.363764] tcp_recvmsg+0x5e/0x1c0 > >>> [ 41.384102] inet_recvmsg+0x42/0x100 > >>> [ 41.406783] ? sock_recvmsg+0x1d/0x70 > >>> [ 41.428201] sock_read_iter+0x84/0xd0 > >>> [ 41.445592] ? 0xffffffffa3000000 > >>> [ 41.462442] new_sync_read+0x148/0x160 > >>> [ 41.479314] ? 0xffffffffa3000000 > >>> [ 41.496937] vfs_read+0x138/0x190 > >>> [ 41.517198] ksys_read+0x87/0xc0 > >>> [ 41.535336] do_syscall_64+0x3b/0x90 > >>> [ 41.551637] entry_SYSCALL_64_after_hwframe+0x44/0xae > >>> [ 41.568050] RIP: 0033:0x48765b > >>> [ 41.583955] Code: e8 4a 35 fe ff eb 88 cc cc cc cc cc cc cc cc e8 fb 7a fe ff 48 8b 7c 24 10 48 8b 74 24 18 48 8b 54 24 20 48 8b 44 24 08 0f 05 <48> 3d 01 f0 ff ff 76 20 48 c7 44 24 28 ff ff ff ff 48 c7 44 24 30 > >>> [ 41.632818] RSP: 002b:000000c000a2f5b8 EFLAGS: 00000212 ORIG_RAX: 0000000000000000 > >>> [ 41.664588] RAX: ffffffffffffffda RBX: 000000c000062000 RCX: 000000000048765b > >>> [ 41.681205] RDX: 0000000000005e54 RSI: 000000c000e66000 RDI: 0000000000000016 > >>> [ 41.697164] RBP: 000000c000a2f608 R08: 0000000000000001 R09: 00000000000001b4 > >>> [ 41.713034] R10: 00000000000000b6 R11: 0000000000000212 R12: 00000000000000e9 > >>> [ 41.728755] R13: 0000000000000001 R14: 000000c000a92000 R15: ffffffffffffffff > >>> [ 41.744254] > >>> [ 41.758585] Modules linked in: br_netfilter bridge veth netconsole virtio_net > >>> > >>> and > >>> > >>> [ 33.524802] BUG: Bad page state in process systemd-network pfn:11e60 > >>> [ 33.528617] page ffffe05dc0147b00 ffffe05dc04e7a00 ffff8ae9851ec000 (1) len 82 offset 252 metasize 4 hroom 0 hdr_len 12 data ffff8ae9851ec10c data_meta ffff8ae9851ec108 data_end ffff8ae9851ec14e > >>> [ 33.529764] page:000000003792b5ba refcount:0 mapcount:-512 mapping:0000000000000000 index:0x0 pfn:0x11e60 > >>> [ 33.532463] flags: 0xfffffc0000000(node=0|zone=1|lastcpupid=0x1fffff) > >>> [ 33.532468] raw: 000fffffc0000000 0000000000000000 dead000000000122 0000000000000000 > >>> [ 33.532470] raw: 0000000000000000 0000000000000000 00000000fffffdff 0000000000000000 > >>> [ 33.532471] page dumped because: nonzero mapcount > >>> [ 33.532472] Modules linked in: br_netfilter bridge veth netconsole virtio_net > >>> [ 33.532479] CPU: 0 PID: 791 Comm: systemd-network Kdump: loaded Not tainted 5.18.0-rc1+ #37 > >>> [ 33.532482] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1.fc35 04/01/2014 > >>> [ 33.532484] Call Trace: > >>> [ 33.532496] > >>> [ 33.532500] dump_stack_lvl+0x45/0x5a > >>> [ 33.532506] bad_page.cold+0x63/0x94 > >>> [ 33.532510] free_pcp_prepare+0x290/0x420 > >>> [ 33.532515] free_unref_page+0x1b/0x100 > >>> [ 33.532518] skb_release_data+0x13f/0x1c0 > >>> [ 33.532524] kfree_skb_reason+0x3e/0xc0 > >>> [ 33.532527] ip6_mc_input+0x23c/0x2b0 > >>> [ 33.532531] ip6_sublist_rcv_finish+0x83/0x90 > >>> [ 33.532534] ip6_sublist_rcv+0x22b/0x2b0 > >>> > >>> [3] XDP program to reproduce(xdp_pass.c): > >>> #include > >>> #include > >>> > >>> SEC("xdp_pass") > >>> int xdp_pkt_pass(struct xdp_md *ctx) > >>> { > >>> bpf_xdp_adjust_head(ctx, -(int)32); > >>> return XDP_PASS; > >>> } > >>> > >>> char _license[] SEC("license") = "GPL"; > >>> > >>> compile: clang -O2 -g -Wall -target bpf -c xdp_pass.c -o xdp_pass.o > >>> load on virtio_net: ip link set enp1s0 xdpdrv obj xdp_pass.o sec xdp_pass > >>> > >>> CC: stable@vger.kernel.org > >>> CC: Jason Wang > >>> CC: Xuan Zhuo > >>> CC: Daniel Borkmann > >>> CC: "Michael S. Tsirkin" > >>> CC: virtualization@lists.linux-foundation.org > >>> Fixes: 8fb7da9e9907 ("virtio_net: get build_skb() buf by data ptr") > >>> Signed-off-by: Nikolay Aleksandrov > >>> --- > >>> drivers/net/virtio_net.c | 8 ++++++-- > >>> 1 file changed, 6 insertions(+), 2 deletions(-) > >>> > >>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > >>> index 87838cbe38cf..0687dd88e97f 100644 > >>> --- a/drivers/net/virtio_net.c > >>> +++ b/drivers/net/virtio_net.c > >>> @@ -434,9 +434,13 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi, > >>> * Buffers with headroom use PAGE_SIZE as alloc size, see > >>> * add_recvbuf_mergeable() + get_mergeable_buf_len() > >>> */ > >>> - truesize = headroom ? PAGE_SIZE : truesize; > >>> + if (headroom) { > >>> + truesize = PAGE_SIZE; > >>> + buf = (char *)((unsigned long)p & PAGE_MASK); > >> > >> The reason for not doing this is that buf and p may not be on the same page, and > >> buf is probably not page-aligned. > >> > >> The implementation of virtio-net merge is add_recvbuf_mergeable(), which > >> allocates a large block of memory at one time, and allocates from it each time. > >> Although in xdp mode, each allocation is page_size, it does not guarantee that > >> each allocation is page-aligned . > >> > >> The problem here is that the value of headroom is wrong, the package is > >> structured like this: > >> > >> from device | headroom | virtio-net hdr | data | > >> after xdp | headroom | virtio-net hdr | meta | data | > > > > You're free to push data back (not necessarily through meta). > > You don't have virtio-net hdr for the xdp case (hdr_valid is false there). > > > >> > >> The page_address(page) + offset we pass to page_to_skb() points to the > >> virtio-net hdr. > >> > >> So I think it might be better to change it this way. > >> > >> Thanks. > >> > >> > >> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > >> index 87838cbe38cf..086ae835ec86 100644 > >> --- a/drivers/net/virtio_net.c > >> +++ b/drivers/net/virtio_net.c > >> @@ -1012,7 +1012,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev, > >> head_skb = page_to_skb(vi, rq, xdp_page, offset, > >> len, PAGE_SIZE, false, > >> metasize, > >> - VIRTIO_XDP_HEADROOM); > >> + VIRTIO_XDP_HEADROOM - metazie); > >> return head_skb; > >> } > >> break; > > > > That patch doesn't fix it, as I said with xdp you can move both data and data_meta. > > So just doing that would take care of the meta, but won't take care of moving data. > > > > Also it doesn't take care of the case where page_to_skb() is called with the original page > i.e. when we already have headroom, so we hit the next/standard page_to_skb() call (xdp_page == page). Yes, you are right. > > The above change guarantees that buf and p will be in the same page How can this be guaranteed? 1. For example, we applied for a 32k buffer first, and took away 1500 + hdr_len from the allocation. 2. set xdp 3. alloc for new buffer The buffer allocated in the third step must be unaligned, and it is entirely possible that p and buf are not on the same page. I fixed my previous patch. Thanks. diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 87838cbe38cf..d95e82255b94 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -1005,6 +1005,8 @@ static struct sk_buff *receive_mergeable(struct net_device *dev, * xdp.data_meta were adjusted */ len = xdp.data_end - xdp.data + vi->hdr_len + metasize; + + headroom = xdp.data - vi->hdr_len - metasize - (buf - headroom); /* We can only create skb based on xdp_page. */ if (unlikely(xdp_page != page)) { rcu_read_unlock(); @@ -1012,7 +1014,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev, head_skb = page_to_skb(vi, rq, xdp_page, offset, len, PAGE_SIZE, false, metasize, - VIRTIO_XDP_HEADROOM); + headroom); return head_skb; } break; _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization