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CVE Record

CVE-2022-49977: ftrace: Fix NULL pointer dereference in is_ftrace_trampoline when ftrace is dead

In the Linux kernel, the following vulnerability has been resolved: ftrace: Fix NULL pointer dereference in is_ftrace_trampoline when ftrace is dead ftrace_startup does not remove ops from ftrace_ops_list when ftrace_startup_enable fails: register_ftrace_function ftrace_startup __register_ftrace_function ... add_ftrace_ops(&ftrace_ops_list, ops) ... ... ftrace_startup_enable // if ftrace failed to modify, ftrace_disabled is set to 1 ... return 0 // ops is in the ftrace_ops_list. When ftrace_disabled = 1, unregister_ftrace_function simply returns without doing anything: unregister_ftrace_function ftrace_shutdown if (unlikely(ftrace_disabled)) return -ENODEV; // return here, __unregister_ftrace_function is not executed, // as a result, ops is still in the ftrace_ops_list __unregister_ftrace_function ... If ops is dynamically allocated, it will be free later, in this case, is_ftrace_trampoline accesses NULL pointer: is_ftrace_trampoline ftrace_ops_trampoline do_for_each_ftrace_op(op, ftrace_ops_list) // OOPS! op may be NULL! Syzkaller reports as follows: [ 1203.506103] BUG: kernel NULL pointer dereference, address: 000000000000010b [ 1203.508039] #PF: supervisor read access in kernel mode [ 1203.508798] #PF: error_code(0x0000) - not-present page [ 1203.509558] PGD 800000011660b067 P4D 800000011660b067 PUD 130fb8067 PMD 0 [ 1203.510560] Oops: 0000 [#1] SMP KASAN PTI [ 1203.511189] CPU: 6 PID: 29532 Comm: syz-executor.2 Tainted: G B W 5.10.0 #8 [ 1203.512324] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014 [ 1203.513895] RIP: 0010:is_ftrace_trampoline+0x26/0xb0 [ 1203.514644] Code: ff eb d3 90 41 55 41 54 49 89 fc 55 53 e8 f2 00 fd ff 48 8b 1d 3b 35 5d 03 e8 e6 00 fd ff 48 8d bb 90 00 00 00 e8 2a 81 26 00 <48> 8b ab 90 00 00 00 48 85 ed 74 1d e8 c9 00 fd ff 48 8d bb 98 00 [ 1203.518838] RSP: 0018:ffffc900012cf960 EFLAGS: 00010246 [ 1203.520092] RAX: 0000000000000000 RBX: 000000000000007b RCX: ffffffff8a331866 [ 1203.521469] RDX: 0000000000000000 RSI: 0000000000000008 RDI: 000000000000010b [ 1203.522583] RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffff8df18b07 [ 1203.523550] R10: fffffbfff1be3160 R11: 0000000000000001 R12: 0000000000478399 [ 1203.524596] R13: 0000000000000000 R14: ffff888145088000 R15: 0000000000000008 [ 1203.525634] FS: 00007f429f5f4700(0000) GS:ffff8881daf00000(0000) knlGS:0000000000000000 [ 1203.526801] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 1203.527626] CR2: 000000000000010b CR3: 0000000170e1e001 CR4: 00000000003706e0 [ 1203.528611] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 1203.529605] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Therefore, when ftrace_startup_enable fails, we need to rollback registration process and remove ops from ftrace_ops_list.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

This is a Linux kernel flaw in the ftrace subsystem. Under a failure path, ftrace can leave a freed or invalid operation on an internal list, later causing a NULL pointer dereference and kernel crash. The sources do not show active exploitation or a CVSS score.

Executive priority

Schedule normal-to-accelerated kernel patching based on system criticality. There is no source evidence of active exploitation, but kernel crash bugs can affect availability and may matter most on shared, high-uptime, or security-sensitive Linux infrastructure.

Technical view

The bug occurs when ftrace_startup_enable fails after ops are added to ftrace_ops_list. Later unregister handling can return early when ftrace_disabled is set, leaving stale ops behind. is_ftrace_trampoline then iterates that list and can dereference NULL or invalid state. Kernel stable commits are referenced as fixes.

Likely exposure

Exposure is most relevant to systems running affected Linux kernel versions or vendor kernels that have not incorporated the referenced stable ftrace fixes. The source bundle lists Linux as affected, but does not provide distribution-specific package names or deployment prevalence.

Exploitation context

The evidence is a syzkaller-triggered kernel crash report. KEV is false, and the bundle provides no cited evidence of real-world exploitation, public weaponization, or remote attack paths. Treat this primarily as a kernel stability and potential denial-of-service issue unless vendor guidance says otherwise.

Researcher notes

The root condition is incomplete rollback of ftrace registration after startup enable failure, leaving stale list state. The source does not establish attacker prerequisites, privilege requirements, or exploitability beyond the syzkaller crash. Avoid assuming remote reachability or privilege escalation without additional vendor analysis.

Mitigation direction

  • Update affected Linux kernels to builds containing the referenced stable ftrace fixes.
  • Use distribution security advisories to map fixed kernel package versions.
  • Prioritize externally exposed multi-user hosts and virtualization platforms for kernel updates.
  • If patching is delayed, monitor for unexplained kernel Oops events involving ftrace.
  • Do not deploy custom kernels missing the referenced stable commits.

Validation and detection

  • Inventory Linux kernel versions across servers, containers hosts, and appliances.
  • Check whether running kernels include the relevant stable ftrace fix commit.
  • Review vendor advisories for package-level fixed versions.
  • Search kernel logs for Oops traces referencing is_ftrace_trampoline or ftrace_ops_trampoline.
  • Confirm reboot into the updated kernel after patch installation.
Prepared
Confidence
medium
Sources
10

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
0ADP providers
9Source links

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

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Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux8a56d7761d2d041ae5e8215d20b4167d8aa93f51, 8a56d7761d2d041ae5e8215d20b4167d8aa93f51, 8a56d7761d2d041ae5e8215d20b4167d8aa93f51, 8a56d7761d2d041ae5e8215d20b4167d8aa93f51, 8a56d7761d2d041ae5e8215d20b4167d8aa93f51, 8a56d7761d2d041ae5e8215d20b4167d8aa93f51, 8a56d7761d2d041ae5e8215d20b4167d8aa93f51, 8a56d7761d2d041ae5e8215d20b4167d8aa93f51, 969a08e9048ddd0d655a19e692673cdb95116ce6, 51d351d5b949ae7204696ada7ef502ed34d34fb0, 2940c25bec92f40a3f7f32504b8ea115d1701892, 189f4e672fc1c086f78818affc810ef29dda42a3unaffected
LinuxLinux3.13, 0, 4.9.327, 4.14.292, 4.19.257, 5.4.212, 5.10.141, 5.15.65, 5.19.7, 6.0affected
Weakness

CWE details

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