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Out-of-bounds Write The advisory has been revoked - it doesn't affect any version of package bpftool  (opens in a new tab)

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  • Snyk IDSNYK-CENTOS7-BPFTOOL-9641232
  • published3 Apr 2025
  • disclosed2 Apr 2025
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Introduced: 2 Apr 2025

CVE-2025-21991  (opens in a new tab)
CWE-787  (opens in a new tab)

Amendment

The Centos security team deemed this advisory irrelevant for Centos:7.

NVD Description

Note: Versions mentioned in the description apply only to the upstream bpftool package and not the bpftool package as distributed by Centos.

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

x86/microcode/AMD: Fix out-of-bounds on systems with CPU-less NUMA nodes

Currently, load_microcode_amd() iterates over all NUMA nodes, retrieves their CPU masks and unconditionally accesses per-CPU data for the first CPU of each mask.

According to Documentation/admin-guide/mm/numaperf.rst:

"Some memory may share the same node as a CPU, and others are provided as memory only nodes."

Therefore, some node CPU masks may be empty and wouldn't have a "first CPU".

On a machine with far memory (and therefore CPU-less NUMA nodes):

  • cpumask_of_node(nid) is 0
  • cpumask_first(0) is CONFIG_NR_CPUS
  • cpu_data(CONFIG_NR_CPUS) accesses the cpu_info per-CPU array at an index that is 1 out of bounds

This does not have any security implications since flashing microcode is a privileged operation but I believe this has reliability implications by potentially corrupting memory while flashing a microcode update.

When booting with CONFIG_UBSAN_BOUNDS=y on an AMD machine that flashes a microcode update. I get the following splat:

UBSAN: array-index-out-of-bounds in arch/x86/kernel/cpu/microcode/amd.c:X:Y index 512 is out of range for type 'unsigned long[512]' [...] Call Trace: dump_stack __ubsan_handle_out_of_bounds load_microcode_amd request_microcode_amd reload_store kernfs_fop_write_iter vfs_write ksys_write do_syscall_64 entry_SYSCALL_64_after_hwframe

Change the loop to go over only NUMA nodes which have CPUs before determining whether the first CPU on the respective node needs microcode update.

[ bp: Massage commit message, fix typo. ]