Subject: CVE-2024-36925: swiotlb: initialise restricted pool list_head when SWIOTLB_DYNAMIC=y

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

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

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

swiotlb: initialise restricted pool list_head when SWIOTLB_DYNAMIC=y

Using restricted DMA pools (CONFIG_DMA_RESTRICTED_POOL=y) in conjunction
with dynamic SWIOTLB (CONFIG_SWIOTLB_DYNAMIC=y) leads to the following
crash when initialising the restricted pools at boot-time:

  | Unable to handle kernel NULL pointer dereference at virtual address 0000000000000008
  | Internal error: Oops: 0000000096000005 [#1] PREEMPT SMP
  | pc : rmem_swiotlb_device_init+0xfc/0x1ec
  | lr : rmem_swiotlb_device_init+0xf0/0x1ec
  | Call trace:
  |  rmem_swiotlb_device_init+0xfc/0x1ec
  |  of_reserved_mem_device_init_by_idx+0x18c/0x238
  |  of_dma_configure_id+0x31c/0x33c
  |  platform_dma_configure+0x34/0x80

faddr2line reveals that the crash is in the list validation code:

  include/linux/list.h:83
  include/linux/rculist.h:79
  include/linux/rculist.h:106
  kernel/dma/swiotlb.c:306
  kernel/dma/swiotlb.c:1695

because add_mem_pool() is trying to list_add_rcu() to a NULL
'mem->pools'.

Fix the crash by initialising the 'mem->pools' list_head in
rmem_swiotlb_device_init() before calling add_mem_pool().

The Linux kernel CVE team has assigned CVE-2024-36925 to this issue.

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

	Issue introduced in 6.6 with commit 1aaa736815eb and fixed in 6.6.31 with commit f2a6b3ed20f2
	Issue introduced in 6.6 with commit 1aaa736815eb and fixed in 6.8.10 with commit f62e0fefcdfe
	Issue introduced in 6.6 with commit 1aaa736815eb and fixed in 6.9 with commit 75961ffb5cb3

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-2024-36925
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:
	kernel/dma/swiotlb.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/f2a6b3ed20f2dea4cb645abc6a73c4595662adca
	https://git.kernel.org/stable/c/f62e0fefcdfe2c05ccb1aa80521a69524eea9c84
	https://git.kernel.org/stable/c/75961ffb5cb3e5196f19cae7683f35cc88b50800