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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	stable@vger.kernel.org,
	Jesper Dangaard Brouer <brouer@redhat.com>,
	Daniel Borkmann <daniel@iogearbox.net>,
	John Fastabend <john.fastabend@gmail.com>
Subject: [PATCH 4.14 23/52] bpf: Remove MTU check in __bpf_skb_max_len
Date: Mon,  5 Apr 2021 10:53:49 +0200
Message-ID: <20210405085022.749537871@linuxfoundation.org> (raw)
In-Reply-To: <20210405085021.996963957@linuxfoundation.org>

From: Jesper Dangaard Brouer <brouer@redhat.com>

commit 6306c1189e77a513bf02720450bb43bd4ba5d8ae upstream.

Multiple BPF-helpers that can manipulate/increase the size of the SKB uses
__bpf_skb_max_len() as the max-length. This function limit size against
the current net_device MTU (skb->dev->mtu).

When a BPF-prog grow the packet size, then it should not be limited to the
MTU. The MTU is a transmit limitation, and software receiving this packet
should be allowed to increase the size. Further more, current MTU check in
__bpf_skb_max_len uses the MTU from ingress/current net_device, which in
case of redirects uses the wrong net_device.

This patch keeps a sanity max limit of SKB_MAX_ALLOC (16KiB). The real limit
is elsewhere in the system. Jesper's testing[1] showed it was not possible
to exceed 8KiB when expanding the SKB size via BPF-helper. The limiting
factor is the define KMALLOC_MAX_CACHE_SIZE which is 8192 for
SLUB-allocator (CONFIG_SLUB) in-case PAGE_SIZE is 4096. This define is
in-effect due to this being called from softirq context see code
__gfp_pfmemalloc_flags() and __do_kmalloc_node(). Jakub's testing showed
that frames above 16KiB can cause NICs to reset (but not crash). Keep this
sanity limit at this level as memory layer can differ based on kernel
config.

[1] https://github.com/xdp-project/bpf-examples/tree/master/MTU-tests

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/161287788936.790810.2937823995775097177.stgit@firesoul
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/core/filter.c |   11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2279,17 +2279,14 @@ static int bpf_skb_net_shrink(struct sk_
 	return 0;
 }
 
-static u32 __bpf_skb_max_len(const struct sk_buff *skb)
-{
-	return skb->dev->mtu + skb->dev->hard_header_len;
-}
+#define BPF_SKB_MAX_LEN SKB_MAX_ALLOC
 
 static int bpf_skb_adjust_net(struct sk_buff *skb, s32 len_diff)
 {
 	bool trans_same = skb->transport_header == skb->network_header;
 	u32 len_cur, len_diff_abs = abs(len_diff);
 	u32 len_min = bpf_skb_net_base_len(skb);
-	u32 len_max = __bpf_skb_max_len(skb);
+	u32 len_max = BPF_SKB_MAX_LEN;
 	__be16 proto = skb->protocol;
 	bool shrink = len_diff < 0;
 	int ret;
@@ -2368,7 +2365,7 @@ static int bpf_skb_trim_rcsum(struct sk_
 BPF_CALL_3(bpf_skb_change_tail, struct sk_buff *, skb, u32, new_len,
 	   u64, flags)
 {
-	u32 max_len = __bpf_skb_max_len(skb);
+	u32 max_len = BPF_SKB_MAX_LEN;
 	u32 min_len = __bpf_skb_min_len(skb);
 	int ret;
 
@@ -2419,7 +2416,7 @@ static const struct bpf_func_proto bpf_s
 BPF_CALL_3(bpf_skb_change_head, struct sk_buff *, skb, u32, head_room,
 	   u64, flags)
 {
-	u32 max_len = __bpf_skb_max_len(skb);
+	u32 max_len = BPF_SKB_MAX_LEN;
 	u32 new_len = skb->len + head_room;
 	int ret;
 



  parent reply index

Thread overview: 56+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-05  8:53 [PATCH 4.14 00/52] 4.14.229-rc1 review Greg Kroah-Hartman
2021-04-05  8:53 ` [PATCH 4.14 01/52] selinux: vsock: Set SID for socket returned by accept() Greg Kroah-Hartman
2021-04-05  8:53 ` [PATCH 4.14 02/52] ipv6: weaken the v4mapped source check Greg Kroah-Hartman
2021-04-05  8:53 ` [PATCH 4.14 03/52] ext4: fix bh ref count on error paths Greg Kroah-Hartman
2021-04-05  8:53 ` [PATCH 4.14 04/52] rpc: fix NULL dereference on kmalloc failure Greg Kroah-Hartman
2021-04-05  8:53 ` [PATCH 4.14 05/52] ASoC: rt5640: Fix dac- and adc- vol-tlv values being off by a factor of 10 Greg Kroah-Hartman
2021-04-05  8:53 ` [PATCH 4.14 06/52] ASoC: rt5651: " Greg Kroah-Hartman
2021-04-05  8:53 ` [PATCH 4.14 07/52] ASoC: sgtl5000: set DAP_AVC_CTRL register to correct default value on probe Greg Kroah-Hartman
2021-04-05  8:53 ` [PATCH 4.14 08/52] ASoC: es8316: Simplify adc_pga_gain_tlv table Greg Kroah-Hartman
2021-04-05  8:53 ` [PATCH 4.14 09/52] ASoC: cs42l42: Fix mixer volume control Greg Kroah-Hartman
2021-04-05  8:53 ` [PATCH 4.14 10/52] ASoC: cs42l42: Always wait at least 3ms after reset Greg Kroah-Hartman
2021-04-05  8:53 ` [PATCH 4.14 11/52] powerpc: Force inlining of cpu_has_feature() to avoid build failure Greg Kroah-Hartman
2021-04-05  8:53 ` [PATCH 4.14 12/52] vhost: Fix vhost_vq_reset() Greg Kroah-Hartman
2021-04-05  8:53 ` [PATCH 4.14 13/52] scsi: st: Fix a use after free in st_open() Greg Kroah-Hartman
2021-04-05  8:53 ` [PATCH 4.14 14/52] scsi: qla2xxx: Fix broken #endif placement Greg Kroah-Hartman
2021-04-05  8:53 ` [PATCH 4.14 15/52] staging: comedi: cb_pcidas: fix request_irq() warn Greg Kroah-Hartman
2021-04-05  8:53 ` [PATCH 4.14 16/52] staging: comedi: cb_pcidas64: " Greg Kroah-Hartman
2021-04-05  8:53 ` [PATCH 4.14 17/52] ASoC: rt5659: Update MCLK rate in set_sysclk() Greg Kroah-Hartman
2021-04-05  8:53 ` [PATCH 4.14 18/52] ext4: do not iput inode under running transaction in ext4_rename() Greg Kroah-Hartman
2021-04-05  8:53 ` [PATCH 4.14 19/52] brcmfmac: clear EAP/association status bits on linkdown events Greg Kroah-Hartman
2021-04-05  8:53 ` [PATCH 4.14 20/52] net: ethernet: aquantia: Handle error cleanup of start on open Greg Kroah-Hartman
2021-04-05  8:53 ` [PATCH 4.14 21/52] appletalk: Fix skb allocation size in loopback case Greg Kroah-Hartman
2021-04-05  8:53 ` [PATCH 4.14 22/52] net: wan/lmc: unregister device when no matching device is found Greg Kroah-Hartman
2021-04-05  8:53 ` Greg Kroah-Hartman [this message]
2021-04-05  8:53 ` [PATCH 4.14 24/52] ALSA: usb-audio: Apply sample rate quirk to Logitech Connect Greg Kroah-Hartman
2021-04-05  8:53 ` [PATCH 4.14 25/52] ALSA: hda/realtek: fix a determine_headset_type issue for a Dell AIO Greg Kroah-Hartman
2021-04-05  8:53 ` [PATCH 4.14 26/52] ALSA: hda/realtek: call alc_update_headset_mode() in hp_automute_hook Greg Kroah-Hartman
2021-04-05  8:53 ` [PATCH 4.14 27/52] tracing: Fix stack trace event size Greg Kroah-Hartman
2021-04-05  8:53 ` [PATCH 4.14 28/52] mm: fix race by making init_zero_pfn() early_initcall Greg Kroah-Hartman
2021-04-05  8:53 ` [PATCH 4.14 29/52] drm/amdgpu: fix offset calculation in amdgpu_vm_bo_clear_mappings() Greg Kroah-Hartman
2021-04-05  8:53 ` [PATCH 4.14 30/52] drm/amdgpu: check alignment on CPU page for bo map Greg Kroah-Hartman
2021-04-05  8:53 ` [PATCH 4.14 31/52] reiserfs: update reiserfs_xattrs_initialized() condition Greg Kroah-Hartman
2021-04-05  8:53 ` [PATCH 4.14 32/52] mm: memcontrol: fix NR_WRITEBACK leak in memcg and system stats Greg Kroah-Hartman
2021-04-05  8:53 ` [PATCH 4.14 33/52] mm: memcg: make sure memory.events is uptodate when waking pollers Greg Kroah-Hartman
2021-04-05  8:54 ` [PATCH 4.14 34/52] mem_cgroup: make sure moving_account, move_lock_task and stat_cpu in the same cacheline Greg Kroah-Hartman
2021-04-05  8:54 ` [PATCH 4.14 35/52] mm: fix oom_kill event handling Greg Kroah-Hartman
2021-04-05  8:54 ` [PATCH 4.14 36/52] mm: writeback: use exact memcg dirty counts Greg Kroah-Hartman
2021-04-05  8:54 ` [PATCH 4.14 37/52] pinctrl: rockchip: fix restore error in resume Greg Kroah-Hartman
2021-04-05  8:54 ` [PATCH 4.14 38/52] extcon: Add stubs for extcon_register_notifier_all() functions Greg Kroah-Hartman
2021-04-05  8:54 ` [PATCH 4.14 39/52] extcon: Fix error handling in extcon_dev_register Greg Kroah-Hartman
2021-04-05  8:54 ` [PATCH 4.14 40/52] firewire: nosy: Fix a use-after-free bug in nosy_ioctl() Greg Kroah-Hartman
2021-04-05  8:54 ` [PATCH 4.14 41/52] usbip: vhci_hcd fix shift out-of-bounds in vhci_hub_control() Greg Kroah-Hartman
2021-04-05  8:54 ` [PATCH 4.14 42/52] USB: quirks: ignore remote wake-up on Fibocom L850-GL LTE modem Greg Kroah-Hartman
2021-04-05  8:54 ` [PATCH 4.14 43/52] usb: musb: Fix suspend with devices connected for a64 Greg Kroah-Hartman
2021-04-05  8:54 ` [PATCH 4.14 44/52] usb: xhci-mtk: fix broken streams issue on 0.96 xHCI Greg Kroah-Hartman
2021-04-05  8:54 ` [PATCH 4.14 45/52] cdc-acm: fix BREAK rx code path adding necessary calls Greg Kroah-Hartman
2021-04-05  8:54 ` [PATCH 4.14 46/52] USB: cdc-acm: untangle a circular dependency between callback and softint Greg Kroah-Hartman
2021-04-05  8:54 ` [PATCH 4.14 47/52] USB: cdc-acm: downgrade message to debug Greg Kroah-Hartman
2021-04-05  8:54 ` [PATCH 4.14 48/52] USB: cdc-acm: fix use-after-free after probe failure Greg Kroah-Hartman
2021-04-05  8:54 ` [PATCH 4.14 49/52] usb: gadget: udc: amd5536udc_pci fix null-ptr-dereference Greg Kroah-Hartman
2021-04-05  8:54 ` [PATCH 4.14 50/52] staging: rtl8192e: Fix incorrect source in memcpy() Greg Kroah-Hartman
2021-04-05  8:54 ` [PATCH 4.14 51/52] staging: rtl8192e: Change state information from u16 to u8 Greg Kroah-Hartman
2021-04-05  8:54 ` [PATCH 4.14 52/52] drivers: video: fbcon: fix NULL dereference in fbcon_cursor() Greg Kroah-Hartman
2021-04-05 17:57 ` [PATCH 4.14 00/52] 4.14.229-rc1 review Guenter Roeck
2021-04-06  7:14 ` Naresh Kamboju
2021-04-07  0:58 ` Samuel Zou

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