CVE-2026-97935tracing: Set the trace clock before registering the histogram trigger

Official description

In the Linux kernel, the following vulnerability has been resolved: tracing: Set the trace clock before registering the histogram trigger hist_register_trigger() puts the trigger on the global named_triggers list in cmd_ops->init(), and only then sets the trace clock: if (data->cmd_ops->init) { ret = data->cmd_ops->init(data); if (ret < 0) goto out; } if (hist_data->enable_timestamps) { ret = tracing_set_clock(file->tr, hist_data->attrs->clock); if (ret) { hist_err(tr, HIST_ERR_SET_CLOCK_FAIL, errpos(clock)); goto out; } The clock string is not checked anywhere before that call, so a named trigger using common_timestamp with an unknown clock fails after it has already become findable. event_hist_trigger_parse() then frees it without taking it off the list, and the next lookup by name reads the freed object: ~# cd /sys/kernel/tracing/events/sched/sched_switch ~# echo 'hist:name=foo:keys=common_pid:ts=common_timestamp:clock=bogus' > trigger bash: echo: write error: Invalid argument ~# echo 'hist:name=foo:keys=common_pid' > trigger BUG: KASAN: slab-use-after-free in find_named_trigger+0xac/0xc0 Read of size 8 at addr ffff88800915d760 by task init/1 find_named_trigger+0xac/0xc0 hist_register_trigger+0xc1/0x900 event_hist_trigger_parse+0x3146/0x6af0 event_trigger_write+0xce/0x160 Freed by task 63: kfree+0x154/0x420 trigger_kthread_fn+0xfd/0x160 Set the clock before the trigger is registered, so that nothing which can fail runs after it is published, the way commit 6f86bdeab633 ("tracing: Fix bad hist from corrupting named_triggers list") moved the registration below the rest of the setup. tracing_set_filter_buffering() is reference counted, so the init failure path has to drop the reference that the clock block now takes first.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/85e6df6e9cd489de8e238596a68b89eee0c03b88
• https://git.kernel.org/stable/c/3568dabef3fb56517777ab981584f72ab1e90186
• https://git.kernel.org/stable/c/c7b77c22adcf314ec8aa4807f01914dcbc62ed54
• https://git.kernel.org/stable/c/578d39ab420b18b76a12fc8d0573ec041a84da28
• https://git.kernel.org/stable/c/cc6c4cf565b0c187c61ffd2e67a4dfb2427675ad
• https://git.kernel.org/stable/c/cfad128171f8e2237a3c723d6478ef2cfb3b9127
• https://git.kernel.org/stable/c/65d1e28198f344832a8a63e8ccf84b8f65b92a32
• https://git.kernel.org/stable/c/6ede78d0563a2a3ae3e46f9c07cedb5d79645429