On 2020-10-22 16:40, Sai Prakash Ranjan wrote:
On 2020-10-22 16:27, Sai Prakash Ranjan wrote:
There was a report of NULL pointer dereference in ETF enable path for perf CS mode with PID monitoring. It is almost 100% reproducible when the process to monitor is something very active such as chrome and with ETF as the sink and not ETR. Currently in a bid to find the pid, the owner is dereferenced via task_pid_nr() call in tmc_enable_etf_sink_perf() and with owner being NULL, we get a NULL pointer dereference.
Looking at the ETR and other places in the kernel, ETF and the ETB are the only places trying to dereference the task(owner) in tmc_enable_etf_sink_perf() which is also called from the sched_in path as in the call trace. Owner(task) is NULL even in the case of ETR in tmc_enable_etr_sink_perf(), but since we cache the PID in alloc_buffer() callback and it is done as part of etm_setup_aux() when allocating buffer for ETR sink, we never dereference this NULL pointer and we are safe. So lets do the same thing with ETF and ETB and cache the PID to which the cs_buffer belongs in alloc_buffer() callback for ETF and ETB as done for ETR. This will also remove the unnecessary function calls (task_pid_nr()) in tmc_enable_etr_sink_perf() and etb_enable_perf().
In addition to this, add a check to validate event->owner before dereferencing it in ETR, ETB and ETF to avoid any possible NULL pointer dereference crashes in their corresponding alloc_buffer callbacks and check for kernel events as well.
Easily reproducible running below:
perf record -e cs_etm/@tmc_etf0/ -N -p <pid>
Unable to handle kernel NULL pointer dereference at virtual address 0000000000000548 Mem abort info: ESR = 0x96000006 EC = 0x25: DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 Data abort info: ISV = 0, ISS = 0x00000006 CM = 0, WnR = 0 <snip>... Call trace: tmc_enable_etf_sink+0xe4/0x280 coresight_enable_path+0x168/0x1fc etm_event_start+0x8c/0xf8 etm_event_add+0x38/0x54 event_sched_in+0x194/0x2ac group_sched_in+0x54/0x12c flexible_sched_in+0xd8/0x120 visit_groups_merge+0x100/0x16c ctx_flexible_sched_in+0x50/0x74 ctx_sched_in+0xa4/0xa8 perf_event_sched_in+0x60/0x6c perf_event_context_sched_in+0x98/0xe0 __perf_event_task_sched_in+0x5c/0xd8 finish_task_switch+0x184/0x1cc schedule_tail+0x20/0xec ret_from_fork+0x4/0x18
Sai Prakash Ranjan (4): perf/core: Export is_kernel_event() coresight: tmc-etf: Fix NULL ptr dereference in tmc_enable_etf_sink_perf() coresight: etb10: Fix possible NULL ptr dereference in etb_enable_perf() coresight: tmc-etr: Fix possible NULL ptr dereference in get_perf_etr_buf_cpu_wide()
drivers/hwtracing/coresight/coresight-etb10.c | 8 +++++++- drivers/hwtracing/coresight/coresight-priv.h | 2 ++ drivers/hwtracing/coresight/coresight-tmc-etf.c | 8 +++++++- drivers/hwtracing/coresight/coresight-tmc-etr.c | 6 +++++- include/linux/perf_event.h | 2 ++ kernel/events/core.c | 3 ++- 6 files changed, 25 insertions(+), 4 deletions(-)
base-commit: f4cb5e9daedf56671badc93ac7f364043aa33886
Please ignore this series, I will need to resend.
Please ignore my previous ignore request and let me know if exporting is_kernel_event() is ok.
Thanks, Sai