Subject: CVE-2024-46763: fou: Fix null-ptr-deref in GRO.

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

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

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

fou: Fix null-ptr-deref in GRO.

We observed a null-ptr-deref in fou_gro_receive() while shutting down
a host.  [0]

The NULL pointer is sk->sk_user_data, and the offset 8 is of protocol
in struct fou.

When fou_release() is called due to netns dismantle or explicit tunnel
teardown, udp_tunnel_sock_release() sets NULL to sk->sk_user_data.
Then, the tunnel socket is destroyed after a single RCU grace period.

So, in-flight udp4_gro_receive() could find the socket and execute the
FOU GRO handler, where sk->sk_user_data could be NULL.

Let's use rcu_dereference_sk_user_data() in fou_from_sock() and add NULL
checks in FOU GRO handlers.

[0]:
BUG: kernel NULL pointer dereference, address: 0000000000000008
 PF: supervisor read access in kernel mode
 PF: error_code(0x0000) - not-present page
PGD 80000001032f4067 P4D 80000001032f4067 PUD 103240067 PMD 0
SMP PTI
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.10.216-204.855.amzn2.x86_64 #1
Hardware name: Amazon EC2 c5.large/, BIOS 1.0 10/16/2017
RIP: 0010:fou_gro_receive (net/ipv4/fou.c:233) [fou]
Code: 41 5f c3 cc cc cc cc e8 e7 2e 69 f4 0f 1f 80 00 00 00 00 0f 1f 44 00 00 49 89 f8 41 54 48 89 f7 48 89 d6 49 8b 80 88 02 00 00 <0f> b6 48 08 0f b7 42 4a 66 25 fd fd 80 cc 02 66 89 42 4a 0f b6 42
RSP: 0018:ffffa330c0003d08 EFLAGS: 00010297
RAX: 0000000000000000 RBX: ffff93d9e3a6b900 RCX: 0000000000000010
RDX: ffff93d9e3a6b900 RSI: ffff93d9e3a6b900 RDI: ffff93dac2e24d08
RBP: ffff93d9e3a6b900 R08: ffff93dacbce6400 R09: 0000000000000002
R10: 0000000000000000 R11: ffffffffb5f369b0 R12: ffff93dacbce6400
R13: ffff93dac2e24d08 R14: 0000000000000000 R15: ffffffffb4edd1c0
FS:  0000000000000000(0000) GS:ffff93daee800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000008 CR3: 0000000102140001 CR4: 00000000007706f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
PKRU: 55555554
Call Trace:
 <IRQ>
 ? show_trace_log_lvl (arch/x86/kernel/dumpstack.c:259)
 ? __die_body.cold (arch/x86/kernel/dumpstack.c:478 arch/x86/kernel/dumpstack.c:420)
 ? no_context (arch/x86/mm/fault.c:752)
 ? exc_page_fault (arch/x86/include/asm/irqflags.h:49 arch/x86/include/asm/irqflags.h:89 arch/x86/mm/fault.c:1435 arch/x86/mm/fault.c:1483)
 ? asm_exc_page_fault (arch/x86/include/asm/idtentry.h:571)
 ? fou_gro_receive (net/ipv4/fou.c:233) [fou]
 udp_gro_receive (include/linux/netdevice.h:2552 net/ipv4/udp_offload.c:559)
 udp4_gro_receive (net/ipv4/udp_offload.c:604)
 inet_gro_receive (net/ipv4/af_inet.c:1549 (discriminator 7))
 dev_gro_receive (net/core/dev.c:6035 (discriminator 4))
 napi_gro_receive (net/core/dev.c:6170)
 ena_clean_rx_irq (drivers/amazon/net/ena/ena_netdev.c:1558) [ena]
 ena_io_poll (drivers/amazon/net/ena/ena_netdev.c:1742) [ena]
 napi_poll (net/core/dev.c:6847)
 net_rx_action (net/core/dev.c:6917)
 __do_softirq (arch/x86/include/asm/jump_label.h:25 include/linux/jump_label.h:200 include/trace/events/irq.h:142 kernel/softirq.c:299)
 asm_call_irq_on_stack (arch/x86/entry/entry_64.S:809)
</IRQ>
 do_softirq_own_stack (arch/x86/include/asm/irq_stack.h:27 arch/x86/include/asm/irq_stack.h:77 arch/x86/kernel/irq_64.c:77)
 irq_exit_rcu (kernel/softirq.c:393 kernel/softirq.c:423 kernel/softirq.c:435)
 common_interrupt (arch/x86/kernel/irq.c:239)
 asm_common_interrupt (arch/x86/include/asm/idtentry.h:626)
RIP: 0010:acpi_idle_do_entry (arch/x86/include/asm/irqflags.h:49 arch/x86/include/asm/irqflags.h:89 drivers/acpi/processor_idle.c:114 drivers/acpi/processor_idle.c:575)
Code: 8b 15 d1 3c c4 02 ed c3 cc cc cc cc 65 48 8b 04 25 40 ef 01 00 48 8b 00 a8 08 75 eb 0f 1f 44 00 00 0f 00 2d d5 09 55 00 fb f4 <fa> c3 cc cc cc cc e9 be fc ff ff 66 66 2e 0f 1f 84 00 00 00 00 00
RSP: 0018:ffffffffb5603e58 EFLAGS: 00000246
RAX: 0000000000004000 RBX: ffff93dac0929c00 RCX: ffff93daee833900
RDX: ffff93daee800000 RSI: ffff93daee87dc00 RDI: ffff93daee87dc64
RBP: 0000000000000001 R08: ffffffffb5e7b6c0 R09: 0000000000000044
R10: ffff93daee831b04 R11: 00000000000001cd R12: 0000000000000001
R13: ffffffffb5e7b740 R14: 0000000000000001 R15: 0000000000000000
 ? sched_clock_cpu (kernel/sched/clock.c:371)
 acpi_idle_enter (drivers/acpi/processor_idle.c:712 (discriminator 3))
 cpuidle_enter_state (drivers/cpuidle/cpuidle.c:237)
 cpuidle_enter (drivers/cpuidle/cpuidle.c:353)
 cpuidle_idle_call (kernel/sched/idle.c:158 kernel/sched/idle.c:239)
 do_idle (kernel/sched/idle.c:302)
 cpu_startup_entry (kernel/sched/idle.c:395 (discriminator 1))
 start_kernel (init/main.c:1048)
 secondary_startup_64_no_verify (arch/x86/kernel/head_64.S:310)
Modules linked in: udp_diag tcp_diag inet_diag nft_nat ipip tunnel4 dummy fou ip_tunnel nft_masq nft_chain_nat nf_nat wireguard nft_ct curve25519_x86_64 libcurve25519_generic nf_conntrack libchacha20poly1305 nf_defrag_ipv6 nf_defrag_ipv4 nft_objref chacha_x86_64 nft_counter nf_tables nfnetlink poly1305_x86_64 ip6_udp_tunnel udp_tunnel libchacha crc32_pclmul ghash_clmulni_intel aesni_intel crypto_simd cryptd glue_helper mousedev psmouse button ena ptp pps_core crc32c_intel
CR2: 0000000000000008

The Linux kernel CVE team has assigned CVE-2024-46763 to this issue.

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

	Issue introduced in 4.7 with commit d92283e338f6 and fixed in 5.10.226 with commit 231c235d2f7a
	Issue introduced in 4.7 with commit d92283e338f6 and fixed in 5.15.167 with commit 4494bccb52ff
	Issue introduced in 4.7 with commit d92283e338f6 and fixed in 6.1.110 with commit d7567f098f54
	Issue introduced in 4.7 with commit d92283e338f6 and fixed in 6.6.51 with commit 1df42be305fe
	Issue introduced in 4.7 with commit d92283e338f6 and fixed in 6.10.10 with commit c46cd6aaca81
	Issue introduced in 4.7 with commit d92283e338f6 and fixed in 6.11 with commit 7e4196935069

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-2024-46763
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/ipv4/fou_core.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/231c235d2f7a66f018f172e26ffd47c363f244ef
	https://git.kernel.org/stable/c/4494bccb52ffda22ce5a1163a776d970e6229e08
	https://git.kernel.org/stable/c/d7567f098f54cb53ee3cee1c82e3d0ed9698b6b3
	https://git.kernel.org/stable/c/1df42be305fe478ded1ee0c1d775f4ece713483b
	https://git.kernel.org/stable/c/c46cd6aaca81040deaea3500ba75126963294bd9
	https://git.kernel.org/stable/c/7e4196935069947d8b70b09c1660b67b067e75cb