xfrm: delete intermediate secpath entry in packet offload mode

JIRA: https://issues.redhat.com/browse/RHEL-84576

commit 600258d
Author: Alexandre Cassen <acassen@corp.free.fr>
Date:   Thu Jan 2 12:11:11 2025 +0200

    xfrm: delete intermediate secpath entry in packet offload mode

    Packets handled by hardware have added secpath as a way to inform XFRM
    core code that this path was already handled. That secpath is not needed
    at all after policy is checked and it is removed later in the stack.

    However, in the case of IP forwarding is enabled (/proc/sys/net/ipv4/ip_forward),
    that secpath is not removed and packets which already were handled are reentered
    to the driver TX path with xfrm_offload set.

    The following kernel panic is observed in mlx5 in such case:

     mlx5_core 0000:04:00.0 enp4s0f0np0: Link up
     mlx5_core 0000:04:00.1 enp4s0f1np1: Link up
     Initializing XFRM netlink socket
     IPsec XFRM device driver
     BUG: kernel NULL pointer dereference, address: 0000000000000000
     #PF: supervisor instruction fetch in kernel mode
     #PF: error_code(0x0010) - not-present page
     PGD 0 P4D 0
     Oops: Oops: 0010 [#1] PREEMPT SMP
     CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 6.13.0-rc1-alex #3
     Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-1ubuntu1.1 04/01/2014
     RIP: 0010:0x0
     Code: Unable to access opcode bytes at 0xffffffffffffffd6.
     RSP: 0018:ffffb87380003800 EFLAGS: 00010206
     RAX: ffff8df004e02600 RBX: ffffb873800038d8 RCX: 00000000ffff98cf
     RDX: ffff8df00733e108 RSI: ffff8df00521fb80 RDI: ffff8df001661f00
     RBP: ffffb87380003850 R08: ffff8df013980000 R09: 0000000000000010
     R10: 0000000000000002 R11: 0000000000000002 R12: ffff8df001661f00
     R13: ffff8df00521fb80 R14: ffff8df00733e108 R15: ffff8df011faf04e
     FS:  0000000000000000(0000) GS:ffff8df46b800000(0000) knlGS:0000000000000000
     CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
     CR2: ffffffffffffffd6 CR3: 0000000106384000 CR4: 0000000000350ef0
     Call Trace:
      <IRQ>
      ? show_regs+0x63/0x70
      ? __die_body+0x20/0x60
      ? __die+0x2b/0x40
      ? page_fault_oops+0x15c/0x550
      ? do_user_addr_fault+0x3ed/0x870
      ? exc_page_fault+0x7f/0x190
      ? asm_exc_page_fault+0x27/0x30
      mlx5e_ipsec_handle_tx_skb+0xe7/0x2f0 [mlx5_core]
      mlx5e_xmit+0x58e/0x1980 [mlx5_core]
      ? __fib_lookup+0x6a/0xb0
      dev_hard_start_xmit+0x82/0x1d0
      sch_direct_xmit+0xfe/0x390
      __dev_queue_xmit+0x6d8/0xee0
      ? __fib_lookup+0x6a/0xb0
      ? internal_add_timer+0x48/0x70
      ? mod_timer+0xe2/0x2b0
      neigh_resolve_output+0x115/0x1b0
      __neigh_update+0x26a/0xc50
      neigh_update+0x14/0x20
      arp_process+0x2cb/0x8e0
      ? __napi_build_skb+0x5e/0x70
      arp_rcv+0x11e/0x1c0
      ? dev_gro_receive+0x574/0x820
      __netif_receive_skb_list_core+0x1cf/0x1f0
      netif_receive_skb_list_internal+0x183/0x2a0
      napi_complete_done+0x76/0x1c0
      mlx5e_napi_poll+0x234/0x7a0 [mlx5_core]
      __napi_poll+0x2d/0x1f0
      net_rx_action+0x1a6/0x370
      ? atomic_notifier_call_chain+0x3b/0x50
      ? irq_int_handler+0x15/0x20 [mlx5_core]
      handle_softirqs+0xb9/0x2f0
      ? handle_irq_event+0x44/0x60
      irq_exit_rcu+0xdb/0x100
      common_interrupt+0x98/0xc0
      </IRQ>
      <TASK>
      asm_common_interrupt+0x27/0x40
     RIP: 0010:pv_native_safe_halt+0xb/0x10
     Code: 09 c3 66 66 2e 0f 1f 84 00 00 00 00 00 66 90 0f 22
     0f 1f 84 00 00 00 00 00 90 eb 07 0f 00 2d 7f e9 36 00 fb
    40 00 83 ff 07 77 21 89 ff ff 24 fd 88 3d a1 bd 0f 21 f8
     RSP: 0018:ffffffffbe603de8 EFLAGS: 00000202
     RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000f92f46680
     RDX: 0000000000000037 RSI: 00000000ffffffff RDI: 00000000000518d4
     RBP: ffffffffbe603df0 R08: 000000cd42e4dffb R09: ffffffffbe603d70
     R10: 0000004d80d62680 R11: 0000000000000001 R12: ffffffffbe60bf40
     R13: 0000000000000000 R14: 0000000000000000 R15: ffffffffbe60aff8
      ? default_idle+0x9/0x20
      arch_cpu_idle+0x9/0x10
      default_idle_call+0x29/0xf0
      do_idle+0x1f2/0x240
      cpu_startup_entry+0x2c/0x30
      rest_init+0xe7/0x100
      start_kernel+0x76b/0xb90
      x86_64_start_reservations+0x18/0x30
      x86_64_start_kernel+0xc0/0x110
      ? setup_ghcb+0xe/0x130
      common_startup_64+0x13e/0x141
      </TASK>
     Modules linked in: esp4_offload esp4 xfrm_interface
    xfrm6_tunnel tunnel4 tunnel6 xfrm_user xfrm_algo binfmt_misc
    intel_rapl_msr intel_rapl_common kvm_amd ccp kvm input_leds serio_raw
    qemu_fw_cfg sch_fq_codel dm_multipath scsi_dh_rdac scsi_dh_emc
    scsi_dh_alua efi_pstore ip_tables x_tables autofs4 raid10 raid456
    async_raid6_recov async_memcpy async_pq raid6_pq async_xor xor async_tx
    libcrc32c raid1 raid0 mlx5_core crct10dif_pclmul crc32_pclmul
    polyval_clmulni polyval_generic ghash_clmulni_intel sha256_ssse3
    sha1_ssse3 ahci mlxfw i2c_i801 libahci i2c_mux i2c_smbus psample
    virtio_rng pci_hyperv_intf aesni_intel crypto_simd cryptd
     CR2: 0000000000000000
     ---[ end trace 0000000000000000 ]---
     RIP: 0010:0x0
     Code: Unable to access opcode bytes at 0xffffffffffffffd6.
     RSP: 0018:ffffb87380003800 EFLAGS: 00010206
     RAX: ffff8df004e02600 RBX: ffffb873800038d8 RCX: 00000000ffff98cf
     RDX: ffff8df00733e108 RSI: ffff8df00521fb80 RDI: ffff8df001661f00
     RBP: ffffb87380003850 R08: ffff8df013980000 R09: 0000000000000010
     R10: 0000000000000002 R11: 0000000000000002 R12: ffff8df001661f00
     R13: ffff8df00521fb80 R14: ffff8df00733e108 R15: ffff8df011faf04e
     FS:  0000000000000000(0000) GS:ffff8df46b800000(0000) knlGS:0000000000000000
     CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
     CR2: ffffffffffffffd6 CR3: 0000000106384000 CR4: 0000000000350ef0
     Kernel panic - not syncing: Fatal exception in interrupt
     Kernel Offset: 0x3b800000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff)
     ---[ end Kernel panic - not syncing: Fatal exception in interrupt ]---

    Fixes: 5958372 ("xfrm: add RX datapath protection for IPsec packet offload mode")
    Signed-off-by: Alexandre Cassen <acassen@corp.free.fr>
    Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
    Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

Signed-off-by: Sabrina Dubroca <sdubroca@redhat.com>

Author: Sabrina Dubroca

include/net/xfrm.h

@@ -1174,9 +1174,19 @@ static inline int __xfrm_policy_check2(struct sock *sk, int dir,
 
 	if (xo) {
 		x = xfrm_input_state(skb);
-		if (x->xso.type == XFRM_DEV_OFFLOAD_PACKET)
-			return (xo->flags & CRYPTO_DONE) &&
-			       (xo->status & CRYPTO_SUCCESS);
+		if (x->xso.type == XFRM_DEV_OFFLOAD_PACKET) {
+			bool check = (xo->flags & CRYPTO_DONE) &&
+				     (xo->status & CRYPTO_SUCCESS);
+
+			/* The packets here are plain ones and secpath was
+			 * needed to indicate that hardware already handled
+			 * them and there is no need to do nothing in addition.
+			 *
+			 * Consume secpath which was set by drivers.
+			 */
+			secpath_reset(skb);
+			return check;
+		}
 	}
 
 	return __xfrm_check_nopolicy(net, skb, dir) ||