[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"repo-stars":3,"vuln-DEBIAN-CVE-2021-46939":6},{"stargazers_count":4,"fetched_at":5},7,"2026-06-04T08:53:30.047Z",{"id":7,"descriptions":8,"cisa":9,"weaknesses":10,"exploits":11,"aliases":12,"duplicate_of":9,"upstream":13,"downstream":16,"duplicates":17,"related":18,"reserved_at":9,"published_at":19,"modified_at":20,"state":9,"summary":21,"references_raw":23,"kevs":30,"epss":9,"epss_history":31,"metrics":32,"affected":39},"DEBIAN-CVE-2021-46939","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",null,[],[],[],[14],{"_key":15},"CVE-2021-46939",[],[],[],"2024-02-27T19:04:05.873Z","2026-04-28T20:23:15.495063Z",{"cisa_kev":22,"cisa_ransomware":22,"cisa_vendor":9,"epss_severity":9,"epss_score":9,"severity":9,"severity_score":9,"severity_version":9,"severity_source":9,"severity_vector":9,"severity_status":9},false,[24],{"url":25,"sources":26,"tags":28},"https://security-tracker.debian.org/tracker/CVE-2021-46939",[27],"osv_debian",[29],"Advisory",[],[],[33],{"source":27,"cvss_v2_0":9,"cvss_v3_0":9,"cvss_v3_1":34,"cvss_v4_0":9},{"baseScore":35,"baseSeverity":9,"vectorString":36,"impactScore":37,"exploitabilityScore":38},5.5,"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",6,4.6,[40],{"ecosystem":41,"name":42,"vendor":43,"product":42,"cpe_part":9,"purl_type":44,"purl_namespace":43,"purl_name":42,"source":9,"versions":45},"Debian","linux","debian","deb",[46,52,53,54],{"version":47,"is_range":48,"range_type":49,"version_start":9,"version_start_type":9,"version_end":50,"version_end_type":51,"fixed_in":9},"lt5_10_38_1",true,"ecosystem","5.10.38-1","excluding",{"version":47,"is_range":48,"range_type":49,"version_start":9,"version_start_type":9,"version_end":50,"version_end_type":51,"fixed_in":9},{"version":47,"is_range":48,"range_type":49,"version_start":9,"version_start_type":9,"version_end":50,"version_end_type":51,"fixed_in":9},{"version":47,"is_range":48,"range_type":49,"version_start":9,"version_start_type":9,"version_end":50,"version_end_type":51,"fixed_in":9}]