CVE-2021-47127

In the Linux kernel, the following vulnerability has been resolved: ice:
track AF_XDP ZC enabled queues in bitmap Commit c7a219048e45 (“ice: Remove
xsk_buff_pool from VSI structure”) silently introduced a regression and
broke the Tx side of AF_XDP in copy mode. xsk_pool on ice_ring is set only
based on the existence of the XDP prog on the VSI which in turn picks
ice_clean_tx_irq_zc to be executed. That is not something that should
happen for copy mode as it should use the regular data path
ice_clean_tx_irq. This results in a following splat when xdpsock is run in
txonly or l2fwd scenarios in copy mode: <snip> [ 106.050195] BUG: kernel
NULL pointer dereference, address: 0000000000000030 [ 106.057269] #PF:
supervisor read access in kernel mode [ 106.062493] #PF: error_code(0x0000)

• not-present page [ 106.067709] PGD 0 P4D 0 [ 106.070293] Oops: 0000 [#1]
  PREEMPT SMP NOPTI [ 106.074721] CPU: 61 PID: 0 Comm: swapper/61 Not tainted
  5.12.0-rc2+ #45 [ 106.081436] Hardware name: Intel Corporation
  S2600WFT/S2600WFT, BIOS SE5C620.86B.02.01.0008.031920191559 03/19/2019 [
  106.092027] RIP: 0010:xp_raw_get_dma+0x36/0x50 [ 106.096551] Code: 74 14 48
  b8 ff ff ff ff ff ff 00 00 48 21 f0 48 c1 ee 30 48 01 c6 48 8b 87 90 00 00
  00 48 89 f2 81 e6 ff 0f 00 00 48 c1 ea 0c <48> 8b 04 d0 48 83 e0 fe 48 01
  f0 c3 66 66 2e 0f 1f 84 00 00 00 00 [ 106.115588] RSP:
  0018:ffffc9000d694e50 EFLAGS: 00010206 [ 106.120893] RAX: 0000000000000000
  RBX: ffff88984b8c8a00 RCX: ffff889852581800 [ 106.128137] RDX:
  0000000000000006 RSI: 0000000000000000 RDI: ffff88984cd8b800 [ 106.135383]
  RBP: ffff888123b50001 R08: ffff889896800000 R09: 0000000000000800 [
  106.142628] R10: 0000000000000000 R11: ffffffff826060c0 R12:
  00000000000000ff [ 106.149872] R13: 0000000000000000 R14: 0000000000000040
  R15: ffff888123b50018 [ 106.157117] FS: 0000000000000000(0000)
  GS:ffff8897e0f40000(0000) knlGS:0000000000000000 [ 106.165332] CS: 0010 DS:
  0000 ES: 0000 CR0: 0000000080050033 [ 106.171163] CR2: 0000000000000030
  CR3: 000000000560a004 CR4: 00000000007706e0 [ 106.178408] DR0:
  0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 106.185653]
  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [
  106.192898] PKRU: 55555554 [ 106.195653] Call Trace: [ 106.198143] <IRQ> [
  106.200196] ice_clean_tx_irq_zc+0x183/0x2a0 [ice] [ 106.205087]
  ice_napi_poll+0x3e/0x590 [ice] [ 106.209356] __napi_poll+0x2a/0x160 [
  106.212911] net_rx_action+0xd6/0x200 [ 106.216634] _do_softirq+0xbf/0x29b
  [ 106.220274] irq_exit_rcu+0x88/0xc0 [ 106.223819]
  common_interrupt+0x7b/0xa0 [ 106.227719] </IRQ> [ 106.229857]
  asm_common_interrupt+0x1e/0x40 </snip> Fix this by introducing the bitmap
  of queues that are zero-copy enabled, where each bit, corresponding to a
  queue id that xsk pool is being configured on, will be set/cleared within
  ice_xsk_pool{en,dis}able and checked within ice_xsk_pool(). The latter is
  a function used for deciding which napi poll routine is executed. Idea is
  being taken from our other drivers such as i40e and ixgbe.