Subject: CVE-2024-26709: powerpc/iommu: Fix the missing iommu_group_put() during platform domain attach

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

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

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

powerpc/iommu: Fix the missing iommu_group_put() during platform domain attach

The function spapr_tce_platform_iommu_attach_dev() is missing to call
iommu_group_put() when the domain is already set. This refcount leak
shows up with BUG_ON() during DLPAR remove operation as:

  KernelBug: Kernel bug in state 'None': kernel BUG at arch/powerpc/platforms/pseries/iommu.c:100!
  Oops: Exception in kernel mode, sig: 5 [#1]
  LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=8192 NUMA pSeries
  <snip>
  Hardware name: IBM,9080-HEX POWER10 (raw) 0x800200 0xf000006 of:IBM,FW1060.00 (NH1060_016) hv:phyp pSeries
  NIP:  c0000000000ff4d4 LR: c0000000000ff4cc CTR: 0000000000000000
  REGS: c0000013aed5f840 TRAP: 0700   Tainted: G          I         (6.8.0-rc3-autotest-g99bd3cb0d12e)
  MSR:  8000000000029033 <SF,EE,ME,IR,DR,RI,LE>  CR: 44002402  XER: 20040000
  CFAR: c000000000a0d170 IRQMASK: 0
  ...
  NIP iommu_reconfig_notifier+0x94/0x200
  LR  iommu_reconfig_notifier+0x8c/0x200
  Call Trace:
    iommu_reconfig_notifier+0x8c/0x200 (unreliable)
    notifier_call_chain+0xb8/0x19c
    blocking_notifier_call_chain+0x64/0x98
    of_reconfig_notify+0x44/0xdc
    of_detach_node+0x78/0xb0
    ofdt_write.part.0+0x86c/0xbb8
    proc_reg_write+0xf4/0x150
    vfs_write+0xf8/0x488
    ksys_write+0x84/0x140
    system_call_exception+0x138/0x330
    system_call_vectored_common+0x15c/0x2ec

The patch adds the missing iommu_group_put() call.

The Linux kernel CVE team has assigned CVE-2024-26709 to this issue.

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

	Issue introduced in 6.7 with commit a8ca9fc9134c and fixed in 6.7.6 with commit c90fdea9cac9
	Issue introduced in 6.7 with commit a8ca9fc9134c and fixed in 6.8 with commit 0846dd77c834

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-2024-26709
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:
	arch/powerpc/kernel/iommu.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/c90fdea9cac9eb419fc266e75d625cb60c8f7f6c
	https://git.kernel.org/stable/c/0846dd77c8349ec92ca0079c9c71d130f34cb192