Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider: - [High] trace: timerlat_fd_release unconditionally resets cpu state --
commit 3a852123b0f7d3294fb2be0fe904429d8ee1fccc Author: Crystal Wood <[email protected]> tracing/osnoise: Refuse timerlat fd open if tracer inactive This commit refuses to open a timerlat file descriptor when there are no active instances. This prevents the file descriptor from remaining active during reconfiguration, which could cause WARN splats. > diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c > index 9ca45b0b8cb39..2511a9b763b98 100644 > --- a/kernel/trace/trace_osnoise.c > +++ b/kernel/trace/trace_osnoise.c > @@ -2506,7 +2506,8 @@ static int timerlat_fd_open(struct inode *inode, struct > file *file) > * This file is accessible only if timerlat is enabled, and > * NO_OSNOISE_WORKLOAD is set. > */ > - if (!timerlat_enabled() || test_bit(OSN_WORKLOAD, &osnoise_options)) > + if (!osnoise_has_registered_instances() || !timerlat_enabled() || > + test_bit(OSN_WORKLOAD, &osnoise_options)) > return -EINVAL; > > guard(migrate)(); [Severity: High] Does this code still allow state corruption during the fd release path? Looking at timerlat_fd_release() in kernel/trace/trace_osnoise.c, osn_reset_cpu() is called unconditionally, bypassing the active session check: kernel/trace/trace_osnoise.c:timerlat_fd_release() { ... if (fdd == osn_var->fdd) timerlat_fd_detach(fdd); osn_reset_cpu(fdd->cpu); ... } Can the following sequence occur? 1. Userspace opens a timerlat fd, creating an active tracing session (fdd1). 2. Tracing is stopped or reconfigured (e.g. via /sys/kernel/tracing/osnoise/cpus), calling stop_kthread(). This detaches fdd1 (osn_var->fdd = NULL) but leaves the fd open in userspace. 3. Tracing is restarted, and userspace opens a new timerlat fd on the same CPU (fdd2). This becomes the active session (osn_var->fdd = fdd2) and tlat_var->timer is initialized and armed. 4. Userspace closes the first fd (fdd1). 5. timerlat_fd_release() is called. Because fdd1 != osn_var->fdd, it skips detachment, but unconditionally calls osn_reset_cpu(fdd1->cpu). Would this unconditional reset wipe the active tracing session's state, including zero-filling the armed hrtimer of the active fdd2 session, potentially leading to timer tree corruption and a kernel panic? -- Sashiko AI review ยท https://sashiko.dev/#/patchset/[email protected]?part=9
