{"id":"CVE-2023-53478","summary":"tracing/synthetic: Fix races on freeing last_cmd","details":"In the Linux kernel, the following vulnerability has been resolved:\n\ntracing/synthetic: Fix races on freeing last_cmd\n\nCurrently, the \"last_cmd\" variable can be accessed by multiple processes\nasynchronously when multiple users manipulate synthetic_events node\nat the same time, it could lead to use-after-free or double-free.\n\nThis patch add \"lastcmd_mutex\" to prevent \"last_cmd\" from being accessed\nasynchronously.\n\n================================================================\n\nIt's easy to reproduce in the KASAN environment by running the two\nscripts below in different shells.\n\nscript 1:\n        while :\n        do\n                echo -n -e '\\x88' \u003e /sys/kernel/tracing/synthetic_events\n        done\n\nscript 2:\n        while :\n        do\n                echo -n -e '\\xb0' \u003e /sys/kernel/tracing/synthetic_events\n        done\n\n================================================================\ndouble-free scenario:\n\n    process A                       process B\n-------------------               ---------------\n1.kstrdup last_cmd\n                                  2.free last_cmd\n3.free last_cmd(double-free)\n\n================================================================\nuse-after-free scenario:\n\n    process A                       process B\n-------------------               ---------------\n1.kstrdup last_cmd\n                                  2.free last_cmd\n3.tracing_log_err(use-after-free)\n\n================================================================\n\nAppendix 1. KASAN report double-free:\n\nBUG: KASAN: double-free in kfree+0xdc/0x1d4\nFree of addr ***** by task sh/4879\nCall trace:\n        ...\n        kfree+0xdc/0x1d4\n        create_or_delete_synth_event+0x60/0x1e8\n        trace_parse_run_command+0x2bc/0x4b8\n        synth_events_write+0x20/0x30\n        vfs_write+0x200/0x830\n        ...\n\nAllocated by task 4879:\n        ...\n        kstrdup+0x5c/0x98\n        create_or_delete_synth_event+0x6c/0x1e8\n        trace_parse_run_command+0x2bc/0x4b8\n        synth_events_write+0x20/0x30\n        vfs_write+0x200/0x830\n        ...\n\nFreed by task 5464:\n        ...\n        kfree+0xdc/0x1d4\n        create_or_delete_synth_event+0x60/0x1e8\n        trace_parse_run_command+0x2bc/0x4b8\n        synth_events_write+0x20/0x30\n        vfs_write+0x200/0x830\n        ...\n\n================================================================\nAppendix 2. KASAN report use-after-free:\n\nBUG: KASAN: use-after-free in strlen+0x5c/0x7c\nRead of size 1 at addr ***** by task sh/5483\nsh: CPU: 7 PID: 5483 Comm: sh\n        ...\n        __asan_report_load1_noabort+0x34/0x44\n        strlen+0x5c/0x7c\n        tracing_log_err+0x60/0x444\n        create_or_delete_synth_event+0xc4/0x204\n        trace_parse_run_command+0x2bc/0x4b8\n        synth_events_write+0x20/0x30\n        vfs_write+0x200/0x830\n        ...\n\nAllocated by task 5483:\n        ...\n        kstrdup+0x5c/0x98\n        create_or_delete_synth_event+0x80/0x204\n        trace_parse_run_command+0x2bc/0x4b8\n        synth_events_write+0x20/0x30\n        vfs_write+0x200/0x830\n        ...\n\nFreed by task 5480:\n        ...\n        kfree+0xdc/0x1d4\n        create_or_delete_synth_event+0x74/0x204\n        trace_parse_run_command+0x2bc/0x4b8\n        synth_events_write+0x20/0x30\n        vfs_write+0x200/0x830\n        ...","modified":"2026-04-02T09:44:16.757236Z","published":"2025-10-01T11:42:47.185Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2023/53xxx/CVE-2023-53478.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/4ccf11c4e8a8e051499d53a12f502196c97a758e"},{"type":"WEB","url":"https://git.kernel.org/stable/c/8826d9e7bd51e7656f78baa4472e8e2f5e7069f0"},{"type":"WEB","url":"https://git.kernel.org/stable/c/9fe183f659a2704255e5d84f6ae308c234a113ec"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2023/53xxx/CVE-2023-53478.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2023-53478"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"27c888da9867725784bad3d6455d6e53b425fa2b"},{"fixed":"9fe183f659a2704255e5d84f6ae308c234a113ec"},{"fixed":"8826d9e7bd51e7656f78baa4472e8e2f5e7069f0"},{"fixed":"4ccf11c4e8a8e051499d53a12f502196c97a758e"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2023-53478.json"}}],"schema_version":"1.7.5"}