[CVE-2026-80817][MODERATE REGULAR] iommu/iommufd: Fix NULL pointer deref in iommufd_ioas_change_process when racing with iopt_map_file_pages

[AL-KERNEL <alkernel@kernelcve.org>]

CVE: CVE-2026-80817
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: iommu/iommufd: Fix NULL pointer deref in iommufd_ioas_change_process when racing with iopt_map_file_pages
Commit: 7596354148c5aa12dfaa17992d1aef1aa2ea831a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7596354148c5aa12dfaa17992d1aef1aa2ea831a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80817
Analysis date: Fri, 04 Sep 2026 15:53:50 -0400
ActionableScore: 3
ActionableScore lower bound: 2
Actionable bucket: Borderline Moderate. Manual review recommended
Manual review required: YES

Summary:
A race in iommufd IOAS handling allows a local process to observe an IOAS area before area pages is initialized, causing a NULL pointer dereference in iommufd_ioas_change_process and leading to a local kernel crash.

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ABOUT THIS REPORT
======================================================================

The original Linux kernel CVE announcement for CVE-2026-80817 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80817

The original announcement does not normally provide a security severity
estimate, CVSS assessment, or enough information to determine whether the
reported kernel bug represents a practically relevant security issue.

This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin. It combines
an autonomous classifier with LLM-assisted technical analysis and a
separate ActionableScore mechanism.

The purpose of this report is to prioritize Linux kernel CVEs before
manual review, identify cases that require prompt investigation, and
support automatic closure of issues that are unlikely to have meaningful
security impact.

Published priority for this report: MODERATE REGULAR
Manual review required: YES

A detailed explanation of the methodology and priority rules is included
at the end of this message.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-80817	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-80817 CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-362;**CWE-476;CWE-667;BEST CVSS score: '4.7';DESCR 'A race in iommufd IOAS handling can expose an IOAS area after it is inserted into the interval tree but before its area pages pointer is initialized. A local process using iommufd ioctls can race iommufd_ioas_change_process with file page mapping and trigger a NULL pointer dereference when the code reads area pages. For the CVSS the PR:L is used because reliable triggering requires local code execution and access to the iommufd interface, not just remote network reachability. The issue is not network reachable and requires a local process context. Impact is denial of service via kernel crash. No UAF, OOB access, information leak, or write primitive is evident from the code path, so confidentiality and integrity impact are not claimed.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline Moderate. Manual review recommended (with actual score 3)	YES	DANGER NULLPTR HARDWARE TEST 	YES	NO	checked

======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================

ActionableScore=3
ActionableScoreLower=2

## 1. ActionableScore

* Conservative score: 2
* Paranoid score: 3
* Final recommended bucket: **Borderline Moderate. Manual review recommended**

## 2. Signal breakdown

Conservative signals:

* Local unprivileged or low privileged trigger: +1
  The crash is triggered through local iommufd ioctls from a local process context. This is PR:L rather than PR:N.

* Reliable kernel crash / strong DoS: +1
  The trace shows a concrete NULL pointer dereference in iommufd_ioas_change_process(), reachable from ioctl, causing kernel Oops or panic depending on system policy.

* Hard or unreliable race / special timing required: -1
  The bug depends on racing iommufd_ioas_change_process() against the two phase iopt_map_pages() path, where area is visible before area->pages is initialized.

* Local high-control kernel object API: +1
  Applied in the paranoid score only. iommufd exposes user controlled IOAS objects and mapping lifetimes, and the bug is specifically in a race between IOAS process change and page mapping state.

Not awarded:

* Generic memory corruption: +0
  The demonstrated primitive is a NULL pointer dereference, not UAF, OOB write, double free, type confusion, or arbitrary write.

* Privilege escalation plausible: +0
  No reclaim, stale object reuse, callback dispatch, write-after-free, or attacker controlled replacement is shown.

* Confidentiality or integrity impact: +0
  The provided code path supports DoS only.

Call-site confidence: high. The ioctl call path and crashing function are present in the supplied trace and patch context.

## 3. Reachability analysis

A local process with access to the iommufd interface can attempt to race IOAS process change against file page mapping. The issue is not network reachable and requires local code execution. Namespace or container impact depends on whether iommufd access is delegated into the environment. In typical deployments this is more likely relevant to virtualization, VFIO, or device assignment setups than to a default general purpose system.

## 4. Severity interpretation

This behaves like an ordinary to borderline Moderate kernel DoS. The realistic impact is local denial of service through a NULL pointer dereference. Theoretical escalation is not supported by the patch because the vulnerable access is a read through a NULL area->pages pointer, not a stale freed object or controlled corruption primitive. The paranoid score is slightly raised only because iommufd is a sensitive kernel object management interface with user controlled mapping lifetimes.

## 5. One-sentence report phrase

A race in iommufd IOAS handling allows a local process to observe an IOAS area before area pages is initialized, causing a NULL pointer dereference in iommufd_ioas_change_process and leading to a local kernel crash.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED. YES REQUIRES MANUAL CHECK.

Reason: this is a kernel race in an IOMMU user API, so it should not be auto-closed purely as a trivial NULL dereference, but current evidence supports DoS only and does not justify Important severity.

======================================================================
UPSTREAM PATCH SUMMARY
======================================================================

Patch: iommu/iommufd: Fix NULL pointer deref in iommufd_ioas_change_process when racing with iopt_map_file_pages
Commit: 7596354148c5aa12dfaa17992d1aef1aa2ea831a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7596354148c5aa12dfaa17992d1aef1aa2ea831a

Commit description:

iommufd_ioas_change_process() iterates every IOAS area while only
holding every IOAS iova_rwsem, so it assumes every area has a non-NULL
pages pointer. That assumption can be false when it runs concurrently
with iopt_map_file_pages().

iopt_map_pages() executes in two phases. It first creates the area and
inserts it into the interval tree under iova_rwsem, with area->pages
still NULL. It then drops iova_rwsem and later fills area->pages
under domains_rwsem. This leaves a window between area creation and
area->pages fill where a concurrent iommufd_ioas_change_process()
can observe the area and dereference a NULL area->pages pointer,
leading to a NULL pointer dereference:

BUG: kernel NULL pointer dereference, address: 00000000000000c0
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 4b655067 P4D 4b655067 PUD 0
Oops: Oops: 0000 [#1] SMP NOPTI
CPU: 0 UID: 0 PID: 11841 Comm: syz.1.628 Not tainted 7.1.0 #3 PREEMPT(full)
Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:iommufd_ioas_change_process+0x419/0xd50 drivers/iommu/iommufd/ioas.c:538
Code: 48 89 c3 48 85 c0 0f 84 cc 00 00 00 e8 10 f5 cb fd 48 8d 7b 68 e8 a7 b5 eb fd 48 8b 6b 68 48 8d bd c0 00 00 00 e8 17 b2 eb fd <8b> ad c0 00 00 00 bf 01 00 00 00 89 ee e8 85 ef cb fd 83 fd 01 74
RSP: 0018:ffffc90015c17d28 EFLAGS: 00010246
RAX: ffff8880186d5328 RBX: ffff88801d25e240 RCX: 0000000080000000
RDX: 00000000000002d7 RSI: ffffffff83ba9e10 RDI: 00000000000000c0
RBP: 0000000000000000 R08: ffffffff8e781eb8 R09: 0000000000000000
R10: 00000000000000c0 R11: ffffffff83ba9e29 R12: ffff88802e216008
R13: ffff88802e216000 R14: 0000000000000001 R15: 0000000000000000
FS:  00007f4aea3f66c0(0000) GS:ffff8880b1fa1000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000000000c0 CR3: 000000004b75c000 CR4: 0000000000350ef0
Call Trace:
 <TASK>
 iommufd_fops_ioctl+0x287/0x400 drivers/iommu/iommufd/main.c:533
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl fs/ioctl.c:583 [inline]
 __x64_sys_ioctl+0x120/0x170 fs/ioctl.c:583
 x64_sys_call+0x1092/0x1fb0 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x10a/0x680 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f4aec1a82bd
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f4aea3f6018 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f4aec436090 RCX: 00007f4aec1a82bd
RDX: 0000200000000180 RSI: 0000000000003b92 RDI: 0000000000000003
RBP: 00007f4aec250295 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f4aec436128 R14: 00007f4aec436090 R15: 00007ffd04ef23e0
 </TASK>
Modules linked in:
CR2: 00000000000000c0
---[ end trace 0000000000000000 ]---
RIP: 0010:iommufd_ioas_change_process+0x419/0xd50 drivers/iommu/iommufd/ioas.c:538
Code: 48 89 c3 48 85 c0 0f 84 cc 00 00 00 e8 10 f5 cb fd 48 8d 7b 68 e8 a7 b5 eb fd 48 8b 6b 68 48 8d bd c0 00 00 00 e8 17 b2 eb fd <8b> ad c0 00 00 00 bf 01 00 00 00 89 ee e8 85 ef cb fd 83 fd 01 74
RSP: 0018:ffffc90015c17d28 EFLAGS: 00010246
RAX: ffff8880186d5328 RBX: ffff88801d25e240 RCX: 0000000080000000
RDX: 00000000000002d7 RSI: ffffffff83ba9e10 RDI: 00000000000000c0
RBP: 0000000000000000 R08: ffffffff8e781eb8 R09: 0000000000000000
R10: 00000000000000c0 R11: ffffffff83ba9e29 R12: ffff88802e216008
R13: ffff88802e216000 R14: 0000000000000001 R15: 0000000000000000
FS:  00007f4aea3f66c0(0000) GS:ffff8880b1fa1000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000000000c0 CR3: 000000004b75c000 CR4: 0000000000350ef0
----------------
Code disassembly (best guess):
   0:	48 89 c3             	mov    %rax,%rbx
   3:	48 85 c0             	test   %rax,%rax
   6:	0f 84 cc 00 00 00    	je     0xd8
   c:	e8 10 f5 cb fd       	call   0xfdcbf521
  11:	48 8d 7b 68          	lea    0x68(%rbx),%rdi
  15:	e8 a7 b5 eb fd       	call   0xfdebb5c1
  1a:	48 8b 6b 68          	mov    0x68(%rbx),%rbp
  1e:	48 8d bd c0 00 00 00 	lea    0xc0(%rbp),%rdi
  25:	e8 17 b2 eb fd       	call   0xfdebb241
* 2a:	8b ad c0 00 00 00    	mov    0xc0(%rbp),%ebp <-- trapping instruction
  30:	bf 01 00 00 00       	mov    $0x1,%edi
  35:	89 ee                	mov    %ebp,%esi
  37:	e8 85 ef cb fd       	call   0xfdcbefc1

[Commit description truncated; see the upstream URL below]

Changed files:
  drivers/iommu/iommufd/ioas.c
  drivers/iommu/iommufd/main.c
  fs/ioctl.c
  arch/x86/include/generated/asm/syscalls_64.h
  arch/x86/entry/syscall_64.c

Diff excerpt:

Not included in this email. See the upstream URL for the full patch.

Full patch:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7596354148c5aa12dfaa17992d1aef1aa2ea831a

======================================================================
DETAILED REPORT METHODOLOGY
======================================================================

The original Linux kernel CVE announcement for CVE-2026-80817 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80817

The original CVE announcement normally does not include a security-level
estimate. In particular, it may not contain a CVSS assessment, an impact
level, or enough information to determine whether the reported bug is a
practically relevant security issue. One purpose of this parallel CVE list
is to provide that missing technical and prioritization information.

The original goal of the AL-KERNEL project was to prioritize Linux kernel
CVE analysis automatically before manual review. The system can also help
identify non-security issues that may be suitable for automatic closure.

This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin.

The first analysis stage combines an autonomous classifier with additional
LLM-based analysis. The autonomous classifier runs locally on a CPU and is
based on a backpropagation neural network. Together, these mechanisms
produce a technical vulnerability description, identify likely weakness
types, estimate CVSS severity, and provide input for ActionableScore.

Two CVSS estimates are retained because incomplete kernel vulnerability
information often permits more than one defensible interpretation:

  Conservative CVSS vector: Not available
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.7

The conservative vector represents a lower-impact interpretation.
The Best/paranoid vector intentionally represents a plausible upper-bound
interpretation and should not automatically be treated as demonstrated
real-world impact.

CVSS may also need to be adjusted for a particular Linux deployment,
because actual reachability, privileges, enabled kernel configuration,
hardware, namespaces, exposed device nodes, and other environmental
conditions can differ significantly between systems.

A separate ActionableScore mechanism evaluates practical remediation
urgency. Its analysis may include reachability, attack prerequisites,
subsystem exposure, memory-corruption characteristics, denial-of-service
reliability, and possible confidentiality, integrity, or
privilege-escalation impact.

  Conservative ActionableScore: 2
  Paranoid ActionableScore: 3

The final base severity is taken directly from the second tab-separated
field of the AL-KERNEL classification result. ActionableScore does not
replace or independently override that final AL-KERNEL decision, and
if ActionableScore adjusted impact level of ALKERNEL, then you would see
self-readable flags above like INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7.

For an AL-KERNEL result of MODERATE, this report uses the following
additional presentation split:

  ActionableScore below 5   -> MODERATE REGULAR
  ActionableScore 5 or more -> MODERATE 7.0

The distinction between MODERATE REGULAR and MODERATE 7.0 makes it
possible to identify Moderate issues that should receive manual analysis
and fixes before lower-priority MODERATE REGULAR issues. In many cases,
MODERATE REGULAR fixes may wait for a later rebase or routine update.

There is one override in which MODERATE REGULAR becomes MODERATE 7.0
even when the ActionableScore is below 5. When the AL-KERNEL result
contains the KPANIC flag, a MODERATE result is always presented as
MODERATE 7.0. The KPANIC flag selected with few regexps without
usage of AI at all, so it helps to detect cases when Kernel Crash happens
and similar (to filter False-Negative results from the LLM usage).

KPANIC indicates that a reliable kernel crash, kernel panic, or similarly
serious kernel availability impact was identified by the classification
workflow.

AL-KERNEL base severity for this report: MODERATE
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): MODERATE REGULAR

These results are intended to support engineering triage. They are
machine-generated estimates, and cases marked for manual review should
be validated by a human security engineer before final disposition.
For more info read docs linked from here: https://kernelcve.org/
(and you can submit you own patch there to generate such a report
for non-existant CVE-id yet).

Note that in many cases this AI tool selects higher severity, than
real is (means you can expect Importants instead of Moderate 7.0 or
Moderates 7.0 instead of regular Moderates). If you see such cases,
please use reply email interface to add additional manual analyses
info to this particular CVE.
And please, please, let me know when you see Lows instead of Importants
or Important instead of Low (because particular for such cases I
need to tune this AI tool to make it better for this one and next similar).
My contact email for such notifications is alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).