Describe CVE-2021-47196.
What is CVE-2021-47196?
In the Linux kernel, the following vulnerability has been resolved:

RDMA/core: Set send and receive CQ before forwarding to the driver

Preset both receive and send CQ pointers prior to call to the drivers and
overwrite it later again till the mlx4 is going to be changed do not
overwrite ibqp properties.

This change is needed for mlx5, because in case of QP creation failure, it
will go to the path of QP destroy which relies on proper CQ pointers.

 BUG: KASAN: use-after-free in create_qp.cold+0x164/0x16e [mlx5_ib]
 Write of size 8 at addr ffff8880064c55c0 by task a.out/246

 CPU: 0 PID: 246 Comm: a.out Not tainted 5.15.0+ #291
 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
 Call Trace:
  dump_stack_lvl+0x45/0x59
  print_address_description.constprop.0+0x1f/0x140
  kasan_report.cold+0x83/0xdf
  create_qp.cold+0x164/0x16e [mlx5_ib]
  mlx5_ib_create_qp+0x358/0x28a0 [mlx5_ib]
  create_qp.part.0+0x45b/0x6a0 [ib_core]
  ib_create_qp_user+0x97/0x150 [ib_core]
  ib_uverbs_handler_UVERBS_METHOD_QP_CREATE+0x92c/0x1250 [ib_uverbs]
  ib_uverbs_cmd_verbs+0x1c38/0x3150 [ib_uverbs]
  ib_uverbs_ioctl+0x169/0x260 [ib_uverbs]
  __x64_sys_ioctl+0x866/0x14d0
  do_syscall_64+0x3d/0x90
  entry_SYSCALL_64_after_hwframe+0x44/0xae

 Allocated by task 246:
  kasan_save_stack+0x1b/0x40
  __kasan_kmalloc+0xa4/0xd0
  create_qp.part.0+0x92/0x6a0 [ib_core]
  ib_create_qp_user+0x97/0x150 [ib_core]
  ib_uverbs_handler_UVERBS_METHOD_QP_CREATE+0x92c/0x1250 [ib_uverbs]
  ib_uverbs_cmd_verbs+0x1c38/0x3150 [ib_uverbs]
  ib_uverbs_ioctl+0x169/0x260 [ib_uverbs]
  __x64_sys_ioctl+0x866/0x14d0
  do_syscall_64+0x3d/0x90
  entry_SYSCALL_64_after_hwframe+0x44/0xae

 Freed by task 246:
  kasan_save_stack+0x1b/0x40
  kasan_set_track+0x1c/0x30
  kasan_set_free_info+0x20/0x30
  __kasan_slab_free+0x10c/0x150
  slab_free_freelist_hook+0xb4/0x1b0
  kfree+0xe7/0x2a0
  create_qp.part.0+0x52b/0x6a0 [ib_core]
  ib_create_qp_user+0x97/0x150 [ib_core]
  ib_uverbs_handler_UVERBS_METHOD_QP_CREATE+0x92c/0x1250 [ib_uverbs]
  ib_uverbs_cmd_verbs+0x1c38/0x3150 [ib_uverbs]
  ib_uverbs_ioctl+0x169/0x260 [ib_uverbs]
  __x64_sys_ioctl+0x866/0x14d0
  do_syscall_64+0x3d/0x90
  entry_SYSCALL_64_after_hwframe+0x44/0xae.