{ "data_version": "4.0", "data_type": "CVE", "data_format": "MITRE", "CVE_data_meta": { "ID": "CVE-2021-46939", "ASSIGNER": "cve@kernel.org", "STATE": "PUBLIC" }, "description": { "description_data": [ { "lang": "eng", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntracing: Restructure trace_clock_global() to never block\n\nIt was reported that a fix to the ring buffer recursion detection would\ncause a hung machine when performing suspend / resume testing. The\nfollowing backtrace was extracted from debugging that case:\n\nCall Trace:\n trace_clock_global+0x91/0xa0\n __rb_reserve_next+0x237/0x460\n ring_buffer_lock_reserve+0x12a/0x3f0\n trace_buffer_lock_reserve+0x10/0x50\n __trace_graph_return+0x1f/0x80\n trace_graph_return+0xb7/0xf0\n ? trace_clock_global+0x91/0xa0\n ftrace_return_to_handler+0x8b/0xf0\n ? pv_hash+0xa0/0xa0\n return_to_handler+0x15/0x30\n ? ftrace_graph_caller+0xa0/0xa0\n ? trace_clock_global+0x91/0xa0\n ? __rb_reserve_next+0x237/0x460\n ? ring_buffer_lock_reserve+0x12a/0x3f0\n ? trace_event_buffer_lock_reserve+0x3c/0x120\n ? trace_event_buffer_reserve+0x6b/0xc0\n ? trace_event_raw_event_device_pm_callback_start+0x125/0x2d0\n ? dpm_run_callback+0x3b/0xc0\n ? pm_ops_is_empty+0x50/0x50\n ? platform_get_irq_byname_optional+0x90/0x90\n ? trace_device_pm_callback_start+0x82/0xd0\n ? dpm_run_callback+0x49/0xc0\n\nWith the following RIP:\n\nRIP: 0010:native_queued_spin_lock_slowpath+0x69/0x200\n\nSince the fix to the recursion detection would allow a single recursion to\nhappen while tracing, this lead to the trace_clock_global() taking a spin\nlock and then trying to take it again:\n\nring_buffer_lock_reserve() {\n trace_clock_global() {\n arch_spin_lock() {\n queued_spin_lock_slowpath() {\n /* lock taken */\n (something else gets traced by function graph tracer)\n ring_buffer_lock_reserve() {\n trace_clock_global() {\n arch_spin_lock() {\n queued_spin_lock_slowpath() {\n /* DEAD LOCK! */\n\nTracing should *never* block, as it can lead to strange lockups like the\nabove.\n\nRestructure the trace_clock_global() code to instead of simply taking a\nlock to update the recorded \"prev_time\" simply use it, as two events\nhappening on two different CPUs that calls this at the same time, really\ndoesn't matter which one goes first. Use a trylock to grab the lock for\nupdating the prev_time, and if it fails, simply try again the next time.\nIf it failed to be taken, that means something else is already updating\nit.\n\n\nBugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=212761" } ] }, "problemtype": { "problemtype_data": [ { "description": [ { "lang": "eng", "value": "n/a" } ] } ] }, "affects": { "vendor": { "vendor_data": [ { "vendor_name": "Linux", "product": { "product_data": [ { "product_name": "Linux", "version": { "version_data": [ { "version_affected": "<", "version_name": "14131f2f98ac", "version_value": "91ca6f6a91f6" }, { "version_value": "not down converted", "x_cve_json_5_version_data": { "versions": [ { "version": "2.6.30", "status": "affected" }, { "version": "0", "lessThan": "2.6.30", "status": "unaffected", "versionType": "custom" }, { "version": "4.4.269", "lessThanOrEqual": "4.4.*", "status": "unaffected", "versionType": "custom" }, { "version": "4.9.269", "lessThanOrEqual": "4.9.*", "status": "unaffected", "versionType": "custom" }, { "version": "4.14.233", "lessThanOrEqual": "4.14.*", "status": "unaffected", "versionType": "custom" }, { "version": "4.19.191", "lessThanOrEqual": "4.19.*", "status": "unaffected", "versionType": "custom" }, { "version": "5.4.118", "lessThanOrEqual": "5.4.*", "status": "unaffected", "versionType": "custom" }, { "version": "5.10.36", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "custom" }, { "version": "5.11.20", "lessThanOrEqual": "5.11.*", "status": "unaffected", "versionType": "custom" }, { "version": "5.12.3", "lessThanOrEqual": "5.12.*", "status": "unaffected", "versionType": "custom" }, { "version": "5.13", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ], "defaultStatus": "affected" } } ] } } ] } } ] } }, "references": { "reference_data": [ { "url": "https://git.kernel.org/stable/c/91ca6f6a91f679c8645d7f3307e03ce86ad518c4", "refsource": "MISC", "name": "https://git.kernel.org/stable/c/91ca6f6a91f679c8645d7f3307e03ce86ad518c4" }, { "url": "https://git.kernel.org/stable/c/859b47a43f5a0e5b9a92b621dc6ceaad39fb5c8b", "refsource": "MISC", "name": "https://git.kernel.org/stable/c/859b47a43f5a0e5b9a92b621dc6ceaad39fb5c8b" }, { "url": "https://git.kernel.org/stable/c/1fca00920327be96f3318224f502e4d5460f9545", "refsource": "MISC", "name": "https://git.kernel.org/stable/c/1fca00920327be96f3318224f502e4d5460f9545" }, { "url": "https://git.kernel.org/stable/c/d43d56dbf452ccecc1ec735cd4b6840118005d7c", "refsource": "MISC", "name": "https://git.kernel.org/stable/c/d43d56dbf452ccecc1ec735cd4b6840118005d7c" }, { "url": "https://git.kernel.org/stable/c/c64da3294a7d59a4bf6874c664c13be892f15f44", "refsource": "MISC", "name": "https://git.kernel.org/stable/c/c64da3294a7d59a4bf6874c664c13be892f15f44" }, { "url": "https://git.kernel.org/stable/c/a33614d52e97fc8077eb0b292189ca7d964cc534", "refsource": "MISC", "name": "https://git.kernel.org/stable/c/a33614d52e97fc8077eb0b292189ca7d964cc534" }, { "url": "https://git.kernel.org/stable/c/6e2418576228eeb12e7ba82edb8f9500623942ff", "refsource": "MISC", "name": "https://git.kernel.org/stable/c/6e2418576228eeb12e7ba82edb8f9500623942ff" }, { "url": "https://git.kernel.org/stable/c/2a1bd74b8186d7938bf004f5603f25b84785f63e", "refsource": "MISC", "name": "https://git.kernel.org/stable/c/2a1bd74b8186d7938bf004f5603f25b84785f63e" }, { "url": "https://git.kernel.org/stable/c/aafe104aa9096827a429bc1358f8260ee565b7cc", "refsource": "MISC", "name": "https://git.kernel.org/stable/c/aafe104aa9096827a429bc1358f8260ee565b7cc" } ] }, "generator": { "engine": "bippy-a5840b7849dd" } }