Subject: CVE-2021-47174: netfilter: nft_set_pipapo_avx2: Add irq_fpu_usable() check, fallback to non-AVX2 version

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

netfilter: nft_set_pipapo_avx2: Add irq_fpu_usable() check, fallback to non-AVX2 version

Arturo reported this backtrace:

[709732.358791] WARNING: CPU: 3 PID: 456 at arch/x86/kernel/fpu/core.c:128 kernel_fpu_begin_mask+0xae/0xe0
[709732.358793] Modules linked in: binfmt_misc nft_nat nft_chain_nat nf_nat nft_counter nft_ct nf_tables nf_conntrack_netlink nfnetlink 8021q garp stp mrp llc vrf intel_rapl_msr intel_rapl_common skx_edac nfit libnvdimm ipmi_ssif x86_pkg_temp_thermal intel_powerclamp coretemp crc32_pclmul mgag200 ghash_clmulni_intel drm_kms_helper cec aesni_intel drm libaes crypto_simd cryptd glue_helper mei_me dell_smbios iTCO_wdt evdev intel_pmc_bxt iTCO_vendor_support dcdbas pcspkr rapl dell_wmi_descriptor wmi_bmof sg i2c_algo_bit watchdog mei acpi_ipmi ipmi_si button nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 ipmi_devintf ipmi_msghandler ip_tables x_tables autofs4 ext4 crc16 mbcache jbd2 dm_mod raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor sd_mod t10_pi crc_t10dif crct10dif_generic raid6_pq libcrc32c crc32c_generic raid1 raid0 multipath linear md_mod ahci libahci tg3 libata xhci_pci libphy xhci_hcd ptp usbcore crct10dif_pclmul crct10dif_common bnxt_en crc32c_intel scsi_mod
[709732.358941]  pps_core i2c_i801 lpc_ich i2c_smbus wmi usb_common
[709732.358957] CPU: 3 PID: 456 Comm: jbd2/dm-0-8 Not tainted 5.10.0-0.bpo.5-amd64 #1 Debian 5.10.24-1~bpo10+1
[709732.358959] Hardware name: Dell Inc. PowerEdge R440/04JN2K, BIOS 2.9.3 09/23/2020
[709732.358964] RIP: 0010:kernel_fpu_begin_mask+0xae/0xe0
[709732.358969] Code: ae 54 24 04 83 e3 01 75 38 48 8b 44 24 08 65 48 33 04 25 28 00 00 00 75 33 48 83 c4 10 5b c3 65 8a 05 5e 21 5e 76 84 c0 74 92 <0f> 0b eb 8e f0 80 4f 01 40 48 81 c7 00 14 00 00 e8 dd fb ff ff eb
[709732.358972] RSP: 0018:ffffbb9700304740 EFLAGS: 00010202
[709732.358976] RAX: 0000000000000001 RBX: 0000000000000003 RCX: 0000000000000001
[709732.358979] RDX: ffffbb9700304970 RSI: ffff922fe1952e00 RDI: 0000000000000003
[709732.358981] RBP: ffffbb9700304970 R08: ffff922fc868a600 R09: ffff922fc711e462
[709732.358984] R10: 000000000000005f R11: ffff922ff0b27180 R12: ffffbb9700304960
[709732.358987] R13: ffffbb9700304b08 R14: ffff922fc664b6c8 R15: ffff922fc664b660
[709732.358990] FS:  0000000000000000(0000) GS:ffff92371fec0000(0000) knlGS:0000000000000000
[709732.358993] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[709732.358996] CR2: 0000557a6655bdd0 CR3: 000000026020a001 CR4: 00000000007706e0
[709732.358999] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[709732.359001] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[709732.359003] PKRU: 55555554
[709732.359005] Call Trace:
[709732.359009]  <IRQ>
[709732.359035]  nft_pipapo_avx2_lookup+0x4c/0x1cba [nf_tables]
[709732.359046]  ? sched_clock+0x5/0x10
[709732.359054]  ? sched_clock_cpu+0xc/0xb0
[709732.359061]  ? record_times+0x16/0x80
[709732.359068]  ? plist_add+0xc1/0x100
[709732.359073]  ? psi_group_change+0x47/0x230
[709732.359079]  ? skb_clone+0x4d/0xb0
[709732.359085]  ? enqueue_task_rt+0x22b/0x310
[709732.359098]  ? bnxt_start_xmit+0x1e8/0xaf0 [bnxt_en]
[709732.359102]  ? packet_rcv+0x40/0x4a0
[709732.359121]  nft_lookup_eval+0x59/0x160 [nf_tables]
[709732.359133]  nft_do_chain+0x350/0x500 [nf_tables]
[709732.359152]  ? nft_lookup_eval+0x59/0x160 [nf_tables]
[709732.359163]  ? nft_do_chain+0x364/0x500 [nf_tables]
[709732.359172]  ? fib4_rule_action+0x6d/0x80
[709732.359178]  ? fib_rules_lookup+0x107/0x250
[709732.359184]  nft_nat_do_chain+0x8a/0xf2 [nft_chain_nat]
[709732.359193]  nf_nat_inet_fn+0xea/0x210 [nf_nat]
[709732.359202]  nf_nat_ipv4_out+0x14/0xa0 [nf_nat]
[709732.359207]  nf_hook_slow+0x44/0xc0
[709732.359214]  ip_output+0xd2/0x100
[709732.359221]  ? __ip_finish_output+0x210/0x210
[709732.359226]  ip_forward+0x37d/0x4a0
[709732.359232]  ? ip4_key_hashfn+0xb0/0xb0
[709732.359238]  ip_sublist_rcv_finish+0x4f/0x60
[709732.359243]  ip_sublist_rcv+0x196/0x220
[709732.359250]  ? ip_rcv_finish_core.isra.22+0x400/0x400
[709732.359255]  ip_list_rcv+0x137/0x160
[709732.359264]  __netif_receive_skb_list_core+0x29b/0x2c0
[709732.359272]  netif_receive_skb_list_internal+0x1a6/0x2d0
[709732.359280]  gro_normal_list.part.156+0x19/0x40
[709732.359286]  napi_complete_done+0x67/0x170
[709732.359298]  bnxt_poll+0x105/0x190 [bnxt_en]
[709732.359304]  ? irqentry_exit+0x29/0x30
[709732.359309]  ? asm_common_interrupt+0x1e/0x40
[709732.359315]  net_rx_action+0x144/0x3c0
[709732.359322]  __do_softirq+0xd5/0x29c
[709732.359329]  asm_call_irq_on_stack+0xf/0x20
[709732.359332]  </IRQ>
[709732.359339]  do_softirq_own_stack+0x37/0x40
[709732.359346]  irq_exit_rcu+0x9d/0xa0
[709732.359353]  common_interrupt+0x78/0x130
[709732.359358]  asm_common_interrupt+0x1e/0x40
[709732.359366] RIP: 0010:crc_41+0x0/0x1e [crc32c_intel]
[709732.359370] Code: ff ff f2 4d 0f 38 f1 93 a8 fe ff ff f2 4c 0f 38 f1 81 b0 fe ff ff f2 4c 0f 38 f1 8a b0 fe ff ff f2 4d 0f 38 f1 93 b0 fe ff ff <f2> 4c 0f 38 f1 81 b8 fe ff ff f2 4c 0f 38 f1 8a b8 fe ff ff f2 4d
[709732.359373] RSP: 0018:ffffbb97008dfcd0 EFLAGS: 00000246
[709732.359377] RAX: 000000000000002a RBX: 0000000000000400 RCX: ffff922fc591dd50
[709732.359379] RDX: ffff922fc591dea0 RSI: 0000000000000a14 RDI: ffffffffc00dddc0
[709732.359382] RBP: 0000000000001000 R08: 000000000342d8c3 R09: 0000000000000000
[709732.359384] R10: 0000000000000000 R11: ffff922fc591dff0 R12: ffffbb97008dfe58
[709732.359386] R13: 000000000000000a R14: ffff922fd2b91e80 R15: ffff922fef83fe38
[709732.359395]  ? crc_43+0x1e/0x1e [crc32c_intel]
[709732.359403]  ? crc32c_pcl_intel_update+0x97/0xb0 [crc32c_intel]
[709732.359419]  ? jbd2_journal_commit_transaction+0xaec/0x1a30 [jbd2]
[709732.359425]  ? irq_exit_rcu+0x3e/0xa0
[709732.359447]  ? kjournald2+0xbd/0x270 [jbd2]
[709732.359454]  ? finish_wait+0x80/0x80
[709732.359470]  ? commit_timeout+0x10/0x10 [jbd2]
[709732.359476]  ? kthread+0x116/0x130
[709732.359481]  ? kthread_park+0x80/0x80
[709732.359488]  ? ret_from_fork+0x1f/0x30
[709732.359494] ---[ end trace 081a19978e5f09f5 ]---

that is, nft_pipapo_avx2_lookup() uses the FPU running from a softirq
that interrupted a kthread, also using the FPU.

That's exactly the reason why irq_fpu_usable() is there: use it, and
if we can't use the FPU, fall back to the non-AVX2 version of the
lookup operation, i.e. nft_pipapo_lookup().

The Linux kernel CVE team has assigned CVE-2021-47174 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 5.7 with commit 7400b063969b and fixed in 5.10.42 with commit b1f45a26bd32
	Issue introduced in 5.7 with commit 7400b063969b and fixed in 5.12.9 with commit 727a2b4fc951
	Issue introduced in 5.7 with commit 7400b063969b and fixed in 5.13 with commit f0b3d338064e

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2021-47174
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	net/netfilter/nft_set_pipapo.c
	net/netfilter/nft_set_pipapo.h
	net/netfilter/nft_set_pipapo_avx2.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/b1f45a26bd322525c14edd9504f6d46dfad679a4
	https://git.kernel.org/stable/c/727a2b4fc951ee69847d4904d98961856ea9fbe6
	https://git.kernel.org/stable/c/f0b3d338064e1fe7531f0d2977e35f3b334abfb4