{"id":"AZL-104526","summary":"CVE-2026-97918 affecting package kernel 6.6.157.1-1","details":"In the Linux kernel, the following vulnerability has been resolved:\n\ntracing: Undo the registration when enabling the histogram trigger fails\n\nCommit 6f86bdeab633 (\"tracing: Fix bad hist from corrupting named_triggers\nlist\") described how a trigger that is registered but not on file-\u003etriggers\nends up freed while still on the global named_triggers list, and moved the\nregistration down so that hist_trigger_enable() follows it immediately. One\npath still gets there. hist_trigger_enable() adds the trigger and takes it\nstraight back out when the event cannot be enabled:\n\n\tlist_add_tail_rcu(&data-\u003elist, &file-\u003etriggers);\n\n\tupdate_cond_flag(file);\n\n\tif (trace_event_trigger_enable_disable(file, 1) \u003c 0) {\n\t\tlist_del_rcu(&data-\u003elist);\n\t\tupdate_cond_flag(file);\n\t\tret--;\n\t}\n\nso the list walk in hist_unregister_trigger() matches nothing, test stays\nNULL, and the -\u003efree() that would call del_named_trigger() is skipped.\nout_unreg falls through to out_free, which frees the trigger anyway:\n\n BUG: KASAN: slab-use-after-free in find_named_trigger+0xac/0xc0\n Read of size 8 at addr ffff8880091d3160 by task init/1\n  find_named_trigger+0xac/0xc0\n  hist_register_trigger+0xc1/0xa00\n  event_hist_trigger_parse+0x3146/0x6af0\n  event_trigger_write+0xce/0x160\n Freed by task 69:\n  kfree+0x154/0x420\n  trigger_kthread_fn+0xfd/0x160\n\nLeave the trigger where hist_unregister_trigger() can find it and let that\nundo the registration, which is the only code that knows all of what\ncmd_ops-\u003einit() took: the named list entry, the hist_pad reference, the\nreference on the trigger a named histogram is shared with, and the copied\ncmd_ops. It also pairs the failed trace_event_trigger_enable_disable(),\nwhose sm_ref and buffered event reference are otherwise left behind.\n\nSince -\u003efree() releases trigger_data and, for a trigger that does not share\nits histogram, hist_data with it, out_unreg can no longer fall through to\nout_free. For a trigger that does share, hist_register_trigger() has\nalready destroyed the caller's hist_data, so the fall-through was reading\nfreed memory there as well.\n\nMove the enable_timestamps check in hist_unregister_trigger() above the\n-\u003efree() call for the same reason: hist_data does not outlive it once the\ntrigger being removed is the one that owns it.","modified":"2026-09-27T05:34:32Z","published":"2026-09-25T11:17:18Z","upstream":["CVE-2026-97918"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-97918"}],"affected":[{"package":{"name":"kernel","ecosystem":"Azure Linux:3","purl":"pkg:rpm/azure-linux/kernel"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"6.6.157.1-1"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-104526.json"}}],"schema_version":"1.9.0"}