Subject: CVE-2021-47615: RDMA/mlx5: Fix releasing unallocated memory in dereg MR flow

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

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

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

RDMA/mlx5: Fix releasing unallocated memory in dereg MR flow

For the case of IB_MR_TYPE_DM the mr does doesn't have a umem, even though
it is a user MR. This causes function mlx5_free_priv_descs() to think that
it is a kernel MR, leading to wrongly accessing mr->descs that will get
wrong values in the union which leads to attempt to release resources that
were not allocated in the first place.

For example:
 DMA-API: mlx5_core 0000:08:00.1: device driver tries to free DMA memory it has not allocated [device address=0x0000000000000000] [size=0 bytes]
 WARNING: CPU: 8 PID: 1021 at kernel/dma/debug.c:961 check_unmap+0x54f/0x8b0
 RIP: 0010:check_unmap+0x54f/0x8b0
 Call Trace:
  debug_dma_unmap_page+0x57/0x60
  mlx5_free_priv_descs+0x57/0x70 [mlx5_ib]
  mlx5_ib_dereg_mr+0x1fb/0x3d0 [mlx5_ib]
  ib_dereg_mr_user+0x60/0x140 [ib_core]
  uverbs_destroy_uobject+0x59/0x210 [ib_uverbs]
  uobj_destroy+0x3f/0x80 [ib_uverbs]
  ib_uverbs_cmd_verbs+0x435/0xd10 [ib_uverbs]
  ? uverbs_finalize_object+0x50/0x50 [ib_uverbs]
  ? lock_acquire+0xc4/0x2e0
  ? lock_acquired+0x12/0x380
  ? lock_acquire+0xc4/0x2e0
  ? lock_acquire+0xc4/0x2e0
  ? ib_uverbs_ioctl+0x7c/0x140 [ib_uverbs]
  ? lock_release+0x28a/0x400
  ib_uverbs_ioctl+0xc0/0x140 [ib_uverbs]
  ? ib_uverbs_ioctl+0x7c/0x140 [ib_uverbs]
  __x64_sys_ioctl+0x7f/0xb0
  do_syscall_64+0x38/0x90

Fix it by reorganizing the dereg flow and mlx5_ib_mr structure:
 - Move the ib_umem field into the user MRs structure in the union as it's
   applicable only there.
 - Function mlx5_ib_dereg_mr() will now call mlx5_free_priv_descs() only
   in case there isn't udata, which indicates that this isn't a user MR.

The Linux kernel CVE team has assigned CVE-2021-47615 to this issue.

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

	Issue introduced in 5.13 with commit f18ec4223117 and fixed in 5.15.10 with commit e3bc4d4b50ca
	Issue introduced in 5.13 with commit f18ec4223117 and fixed in 5.15.14 with commit c44979ace49b
	Issue introduced in 5.13 with commit f18ec4223117 and fixed in 5.16 with commit f0ae4afe3d35

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-2021-47615
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:
	drivers/infiniband/hw/mlx5/mlx5_ib.h
	drivers/infiniband/hw/mlx5/mr.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/e3bc4d4b50cae7db08e50dbe43f771c906e97701
	https://git.kernel.org/stable/c/c44979ace49b4aede3cc7cb5542316e53a4005c9
	https://git.kernel.org/stable/c/f0ae4afe3d35e67db042c58a52909e06262b740f