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CVE Record

CVE-2022-50635: powerpc/kprobes: Fix null pointer reference in arch_prepare_kprobe()

In the Linux kernel, the following vulnerability has been resolved: powerpc/kprobes: Fix null pointer reference in arch_prepare_kprobe() I found a null pointer reference in arch_prepare_kprobe(): # echo 'p cmdline_proc_show' > kprobe_events # echo 'p cmdline_proc_show+16' >> kprobe_events Kernel attempted to read user page (0) - exploit attempt? (uid: 0) BUG: Kernel NULL pointer dereference on read at 0x00000000 Faulting instruction address: 0xc000000000050bfc Oops: Kernel access of bad area, sig: 11 [#1] LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA PowerNV Modules linked in: CPU: 0 PID: 122 Comm: sh Not tainted 6.0.0-rc3-00007-gdcf8e5633e2e #10 NIP: c000000000050bfc LR: c000000000050bec CTR: 0000000000005bdc REGS: c0000000348475b0 TRAP: 0300 Not tainted (6.0.0-rc3-00007-gdcf8e5633e2e) MSR: 9000000000009033 <SF,HV,EE,ME,IR,DR,RI,LE> CR: 88002444 XER: 20040006 CFAR: c00000000022d100 DAR: 0000000000000000 DSISR: 40000000 IRQMASK: 0 ... NIP arch_prepare_kprobe+0x10c/0x2d0 LR arch_prepare_kprobe+0xfc/0x2d0 Call Trace: 0xc0000000012f77a0 (unreliable) register_kprobe+0x3c0/0x7a0 __register_trace_kprobe+0x140/0x1a0 __trace_kprobe_create+0x794/0x1040 trace_probe_create+0xc4/0xe0 create_or_delete_trace_kprobe+0x2c/0x80 trace_parse_run_command+0xf0/0x210 probes_write+0x20/0x40 vfs_write+0xfc/0x450 ksys_write+0x84/0x140 system_call_exception+0x17c/0x3a0 system_call_vectored_common+0xe8/0x278 --- interrupt: 3000 at 0x7fffa5682de0 NIP: 00007fffa5682de0 LR: 0000000000000000 CTR: 0000000000000000 REGS: c000000034847e80 TRAP: 3000 Not tainted (6.0.0-rc3-00007-gdcf8e5633e2e) MSR: 900000000280f033 <SF,HV,VEC,VSX,EE,PR,FP,ME,IR,DR,RI,LE> CR: 44002408 XER: 00000000 The address being probed has some special: cmdline_proc_show: Probe based on ftrace cmdline_proc_show+16: Probe for the next instruction at the ftrace location The ftrace-based kprobe does not generate kprobe::ainsn::insn, it gets set to NULL. In arch_prepare_kprobe() it will check for: ... prev = get_kprobe(p->addr - 1); preempt_enable_no_resched(); if (prev && ppc_inst_prefixed(ppc_inst_read(prev->ainsn.insn))) { ... If prev is based on ftrace, 'ppc_inst_read(prev->ainsn.insn)' will occur with a null pointer reference. At this point prev->addr will not be a prefixed instruction, so the check can be skipped. Check if prev is ftrace-based kprobe before reading 'prev->ainsn.insn' to fix this problem. [mpe: Trim oops]

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

A Linux kernel bug on PowerPC can crash the kernel when certain tracing probes are registered. The main business risk is availability disruption on affected PowerPC systems. Provided sources do not show active exploitation, and the example requires root-level tracing access.

Executive priority

Treat as a targeted availability issue for PowerPC Linux infrastructure. Prioritize patching where these systems support production workloads or allow multiple administrators privileged shell access.

Technical view

The flaw is a NULL pointer dereference in powerpc arch_prepare_kprobe(). An ftrace-based kprobe may have prev->ainsn.insn set to NULL, but the code reads it while checking prefixed instructions, causing an oops. Stable kernel commits add a check for ftrace-based kprobes before dereferencing.

Likely exposure

Exposure appears limited to Linux systems on PowerPC using kprobes/ftrace tracing. The described trigger involves writing probe definitions through kernel tracing interfaces, which typically requires privileged local access. Non-PowerPC systems are not indicated as affected in the provided sources.

Exploitation context

The source shows a local crash scenario, not remote compromise. No KEV listing or cited source indicates active exploitation. The practical risk is local denial of service by an administrator or compromised privileged account with access to tracing facilities.

Researcher notes

Version metadata in the provided bundle is incomplete and flattened. The clearest technical evidence is the upstream stable commit set and CVE description. Validate using vendor kernel changelogs because distributions may backport fixes without changing major kernel versions.

Mitigation direction

  • Update affected PowerPC Linux kernels to vendor builds containing the referenced stable fixes.
  • Check Linux distribution advisories for exact package versions and backports.
  • Restrict access to kernel tracing interfaces to trusted administrators only.
  • Monitor for kernel oops events involving arch_prepare_kprobe.

Validation and detection

  • Inventory PowerPC Linux hosts and their kernel versions.
  • Confirm whether kprobes, ftrace, or tracefs are enabled and accessible.
  • Compare deployed kernels with vendor advisories or referenced stable commits.
  • Review system logs for NULL pointer dereferences in arch_prepare_kprobe.
Prepared
Confidence
medium
Sources
6

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

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0CVSS vectors
0Timeline events
0ADP providers
5Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxb4657f7650babc9bfb41ce875abe41b18604a105, b4657f7650babc9bfb41ce875abe41b18604a105, b4657f7650babc9bfb41ce875abe41b18604a105, b4657f7650babc9bfb41ce875abe41b18604a105unaffected
LinuxLinux5.8, 0, 5.15.75, 5.19.17, 6.0.3, 6.1affected
Weakness

CWE details

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