🛡️ CVE-2024-46763 — kernel

fou: Fix null-ptr-deref in GRO.

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: ffff93d

---truncated---