From: Kyle Zeng Date: Thu, 6 Aug 2026 20:56:55 +0000 (-0700) Subject: perf: Reject exited events as group leaders X-Git-Tag: v7.2~6^2~1 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=fa091f46c3833fb22384f10eade2b4e1e1d0b278;p=thirdparty%2Fkernel%2Flinux.git perf: Reject exited events as group leaders perf_event_remove_on_exec() sets remove-on-exec events to the EXIT state and detaches their group relationships. The event's file descriptor can remain open, however, and perf_event_open() currently accepts that event as a group leader because its early validation rejects only REVOKED and DEAD events. A new sibling can consequently be linked to the detached leader. When the leader is closed, perf_group_detach() observes that its PERF_ATTACH_GROUP bit is already clear and skips the new sibling. The sibling then retains a group_leader pointer to the freed event. Reject group leaders in the EXIT state. Perform the check while holding the shared context mutex so that an exec in the target task cannot detach the leader between validation and group attachment. [peterz: make the earlier test fully consistent] Fixes: 037a3c43edfb ("perf/core: Detach event groups during remove_on_exec") Assisted-by: Codex:gpt-5.6-sol Signed-off-by: Kyle Zeng Signed-off-by: Peter Zijlstra (Intel) Link: https://patch.msgid.link/20260806205655.75722-1-kylebot@openai.com --- diff --git a/kernel/events/core.c b/kernel/events/core.c index ba5bd6a78fe7..bd25e1998faf 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -13972,7 +13972,7 @@ SYSCALL_DEFINE5(perf_event_open, goto err_fd; } group_leader = fd_file(group)->private_data; - if (group_leader->state <= PERF_EVENT_STATE_REVOKED) { + if (group_leader->state <= PERF_EVENT_STATE_EXIT) { err = -ENODEV; goto err_fd; } @@ -14103,6 +14103,12 @@ SYSCALL_DEFINE5(perf_event_open, if (group_leader->ctx != ctx) goto err_locked; + /* Recheck under ctx::mutex to serialize against remove-on-exec. */ + if (group_leader->state <= PERF_EVENT_STATE_EXIT) { + err = -ENODEV; + goto err_locked; + } + /* * Only a group leader can be exclusive or pinned */