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Alma Linux: CVE-2021-46939: Important: kernel security update (Multiple Advisories)

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Alma Linux: CVE-2021-46939: Important: kernel security update (Multiple Advisories)

Severity
5
CVSS
(AV:L/AC:L/Au:S/C:N/I:N/A:C)
Published
02/27/2024
Created
08/13/2024
Added
08/12/2024
Modified
01/30/2025

Description

In the Linux kernel, the following vulnerability has been resolved: tracing: Restructure trace_clock_global() to never block It was reported that a fix to the ring buffer recursion detection would cause a hung machine when performing suspend / resume testing. The following backtrace was extracted from debugging that case: Call Trace: trace_clock_global+0x91/0xa0 __rb_reserve_next+0x237/0x460 ring_buffer_lock_reserve+0x12a/0x3f0 trace_buffer_lock_reserve+0x10/0x50 __trace_graph_return+0x1f/0x80 trace_graph_return+0xb7/0xf0 ? trace_clock_global+0x91/0xa0 ftrace_return_to_handler+0x8b/0xf0 ? pv_hash+0xa0/0xa0 return_to_handler+0x15/0x30 ? ftrace_graph_caller+0xa0/0xa0 ? trace_clock_global+0x91/0xa0 ? __rb_reserve_next+0x237/0x460 ? ring_buffer_lock_reserve+0x12a/0x3f0 ? trace_event_buffer_lock_reserve+0x3c/0x120 ? trace_event_buffer_reserve+0x6b/0xc0 ? trace_event_raw_event_device_pm_callback_start+0x125/0x2d0 ? dpm_run_callback+0x3b/0xc0 ? pm_ops_is_empty+0x50/0x50 ? platform_get_irq_byname_optional+0x90/0x90 ? trace_device_pm_callback_start+0x82/0xd0 ? dpm_run_callback+0x49/0xc0 With the following RIP: RIP: 0010:native_queued_spin_lock_slowpath+0x69/0x200 Since the fix to the recursion detection would allow a single recursion to happen while tracing, this lead to the trace_clock_global() taking a spin lock and then trying to take it again: ring_buffer_lock_reserve() { trace_clock_global() { arch_spin_lock() { queued_spin_lock_slowpath() { /* lock taken */ (something else gets traced by function graph tracer) ring_buffer_lock_reserve() { trace_clock_global() { arch_spin_lock() { queued_spin_lock_slowpath() { /* DEAD LOCK! */ Tracing should *never* block, as it can lead to strange lockups like the above. Restructure the trace_clock_global() code to instead of simply taking a lock to update the recorded "prev_time" simply use it, as two events happening on two different CPUs that calls this at the same time, really doesn't matter which one goes first. Use a trylock to grab the lock for updating the prev_time, and if it fails, simply try again the next time. If it failed to be taken, that means something else is already updating it. Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=212761

Solution(s)

  • alma-upgrade-bpftool
  • alma-upgrade-kernel
  • alma-upgrade-kernel-abi-stablelists
  • alma-upgrade-kernel-core
  • alma-upgrade-kernel-cross-headers
  • alma-upgrade-kernel-debug
  • alma-upgrade-kernel-debug-core
  • alma-upgrade-kernel-debug-devel
  • alma-upgrade-kernel-debug-modules
  • alma-upgrade-kernel-debug-modules-extra
  • alma-upgrade-kernel-devel
  • alma-upgrade-kernel-doc
  • alma-upgrade-kernel-headers
  • alma-upgrade-kernel-modules
  • alma-upgrade-kernel-modules-extra
  • alma-upgrade-kernel-rt
  • alma-upgrade-kernel-rt-core
  • alma-upgrade-kernel-rt-debug
  • alma-upgrade-kernel-rt-debug-core
  • alma-upgrade-kernel-rt-debug-devel
  • alma-upgrade-kernel-rt-debug-kvm
  • alma-upgrade-kernel-rt-debug-modules
  • alma-upgrade-kernel-rt-debug-modules-extra
  • alma-upgrade-kernel-rt-devel
  • alma-upgrade-kernel-rt-kvm
  • alma-upgrade-kernel-rt-modules
  • alma-upgrade-kernel-rt-modules-extra
  • alma-upgrade-kernel-tools
  • alma-upgrade-kernel-tools-libs
  • alma-upgrade-kernel-tools-libs-devel
  • alma-upgrade-kernel-zfcpdump
  • alma-upgrade-kernel-zfcpdump-core
  • alma-upgrade-kernel-zfcpdump-devel
  • alma-upgrade-kernel-zfcpdump-modules
  • alma-upgrade-kernel-zfcpdump-modules-extra
  • alma-upgrade-perf
  • alma-upgrade-python3-perf

References

  • https://attackerkb.com/topics/cve-2021-46939
  • CVE - 2021-46939
  • https://errata.almalinux.org/8/ALSA-2024-5101.html
  • https://errata.almalinux.org/8/ALSA-2024-5102.html
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  • 已创建
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