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206b25c090
linux/kernel/trace
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Martin Kaiser 206b25c090 tracing: eprobe: read the complete FILTER_PTR_STRING pointer 
For a char * element in an event, the FILTER_PTR_STRING filter type is
used. When the event occurs, a pointer is stored in the ringbuffer.

If an eprobe references such a char * element of a "base event", the
stored pointer is truncated when it's read from the ringbuffer.

$ cd /sys/kernel/tracing
$ echo 'e rcu.rcu_utilization $s:x64 $s:string' > dynamic_events
$ echo 1 > tracing_on
$ echo 1 > events/eprobes/enable
$ sleep 1
$ echo 0 > events/eprobes/enable
$ cat trace
   <idle>-0  ...: (rcu.rcu_utilization) arg1=0x4f arg2=(fault)
   <idle>-0  ...: (rcu.rcu_utilization) arg1=0x2 arg2=(fault)

The problem is in get_event_field

	val = (unsigned long)(*(char *)addr);

addr points to the position in the ringbuffer where the pointer was
stored. The assignment reads only the lowest byte of the pointer.

Fix the cast to read the whole pointer. The output of the test above
is now

<idle>-0 ... arg1=0xffffffff81c7d3f3 arg2="Start scheduler-tick"
<idle>-0 ... arg1=0xffffffff81c57340 arg2="End scheduler-tick"

Link: https://lore.kernel.org/all/20260620145339.3234726-1-martin@kaiser.cx/

Fixes: f04dec9346 ("tracing/eprobes: Fix reading of string fields")
Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
2026-06-30 23:58:19 +09:00
..
rv rv: Use 0 to check preemption enabled in opid 2026-06-03 12:33:25 +02:00
blktrace.c block-7.0-20260305 2026-03-06 08:36:18 -08:00
bpf_trace.c bpf: Add support to specify uprobe_multi target via file descriptor 2026-06-14 17:24:25 -07:00
bpf_trace.h tracing/treewide: Remove second parameter of __assign_str() 2024-05-22 20:14:47 -04:00
error_report-traces.c
fgraph.c fgraph: Do not call handlers direct when not using ftrace_ops 2026-02-19 15:21:22 -05:00
fprobe.c fprobe: Fix unregister_fprobe() to wait for RCU grace period 2026-05-11 19:04:46 +09:00
ftrace_internal.h function_graph: Make fgraph_update_pid_func() a stub for !DYNAMIC_FTRACE 2024-06-10 18:08:23 -04:00
ftrace.c ftrace: Add add_ftrace_hash_entry function 2026-06-07 10:03:00 -07:00
Kconfig ring-buffer: Add persistent ring buffer invalid-page inject test 2026-05-28 22:40:51 -04:00
kprobe_event_gen_test.c
Makefile tracing: Updates for v7.2: 2026-06-18 20:53:00 -07:00
pid_list.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
pid_list.h trace/pid_list: optimize pid_list->lock contention 2025-11-13 15:15:54 -05:00
power-traces.c PM: cpufreq: powernv/tracing: Move powernv_throttle trace event 2025-07-21 16:40:56 -04:00
preemptirq_delay_test.c kernel: trace: preemptirq_delay_test: use offstack cpu mask 2025-07-08 18:17:38 -04:00
remote_test_events.h tracing: Add a trace remote module for testing 2026-03-09 12:33:55 -04:00
remote_test.c tracing: Fix desc in error path for the trace remote test module 2026-05-16 16:11:04 -04:00
rethook.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
ring_buffer_benchmark.c tracing: Fix typo in ring_buffer_benchmark.c 2025-12-05 15:43:40 -05:00
ring_buffer.c ring-buffer: Updates for v7.2: 2026-06-18 21:23:22 -07:00
rpm-traces.c
simple_ring_buffer.c tracing: Fix unload_page for simple_ring_buffer init rollback 2026-05-21 08:26:22 -04:00
synth_event_gen_test.c tracing / synthetic: Disable events after testing in synth_event_gen_test_init() 2023-12-21 10:04:45 -05:00
trace_benchmark.c tracing: Improve benchmark test performance by using do_div() 2024-05-13 20:00:57 -04:00
trace_benchmark.h
trace_boot.c tracing: Make the backup instance non-reusable 2026-04-02 13:20:38 -04:00
trace_branch.c tracing/branch: Use pr_warn() instead of printk(KERN_WARNING) 2026-05-21 18:03:08 -04:00
trace_btf.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
trace_btf.h tracing/probes: Add a function to search a member of a struct/union 2023-08-23 09:40:16 +09:00
trace_clock.c tracing: Use atomic64_inc_return() in trace_clock_counter() 2024-10-09 19:59:49 -04:00
trace_dynevent.c tracing: Report wrong dynamic event command 2025-11-10 19:26:14 -05:00
trace_dynevent.h tracing: probes: Fix a possible race in trace_probe_log APIs 2025-05-13 22:23:34 +09:00
trace_entries.h tracing: Fix ftrace event field alignments 2026-02-05 09:47:11 -05:00
trace_eprobe.c tracing: eprobe: read the complete FILTER_PTR_STRING pointer 2026-06-30 23:58:19 +09:00
trace_event_perf.c perf/ftrace: Fix WARNING in __unregister_ftrace_function 2026-05-29 11:27:40 -04:00
trace_events_filter_test.h
trace_events_filter.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
trace_events_hist.c tracing: Turn hist_elt_data field_var_str into a flexible array 2026-05-29 11:20:47 -04:00
trace_events_inject.c tracing: Have format file honor EVENT_FILE_FL_FREED 2024-08-07 18:12:46 -04:00
trace_events_synth.c tracing: Allow perf to read synthetic events 2026-05-21 18:03:07 -04:00
trace_events_trigger.c tracing: Drain deferred trigger frees if kthread creation fails 2026-03-28 08:32:44 -04:00
trace_events_user.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
trace_events.c tracing updates for v7.1: 2026-04-17 09:43:12 -07:00
trace_export.c tracing: Fix ftrace event field alignments 2026-02-05 09:47:11 -05:00
trace_fprobe.c Convert 'alloc_flex' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
trace_functions_graph.c fgraph: Fix thresh_return nosleeptime double-adjust 2026-03-03 22:11:20 -05:00
trace_functions.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
trace_hwlat.c tracing: Fix false sharing in hwlat get_sample() 2026-02-10 03:36:39 -05:00
trace_irqsoff.c tracing: Allow tracer to add more than 32 options 2025-11-04 21:44:00 +09:00
trace_kdb.c tracing: Allow tracer to add more than 32 options 2025-11-04 21:44:00 +09:00
trace_kprobe_selftest.c
trace_kprobe_selftest.h
trace_kprobe.c tracing updates for v7.1: 2026-04-17 09:43:12 -07:00
trace_mmiotrace.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
trace_nop.c
trace_osnoise.c tracing/osnoise: Array printk init and cleanup 2026-05-29 10:40:27 -04:00
trace_output.c tracing updates for v7.1: 2026-04-17 09:43:12 -07:00
trace_output.h tracing: Allow tracer to add more than 32 options 2025-11-04 21:44:00 +09:00
trace_pid.c tracing: Move pid filtering into trace_pid.c 2026-02-08 21:01:13 -05:00
trace_preemptirq.c tracing: Fix archs that still call tracepoints without RCU watching 2024-12-05 09:28:58 -05:00
trace_printk.c tracing: move __printf() attribute on __ftrace_vbprintk() 2026-03-23 20:16:45 -04:00
trace_probe_kernel.h
trace_probe_tmpl.h tracing/fprobe: Enable fprobe events with CONFIG_DYNAMIC_FTRACE_WITH_ARGS 2024-12-26 10:50:04 -05:00
trace_probe.c tracing/probes: Remove WARN_ON_ONCE from parse_btf_arg 2026-06-30 23:58:19 +09:00
trace_probe.h tracing: probes: fix typo in a log message 2026-06-25 08:34:45 +09:00
trace_recursion_record.c tracing: Switch trace_recursion_record.c code over to use guard() 2026-05-21 18:03:07 -04:00
trace_remote.c tracing: Remove redundant IS_ERR() check in trace_pipe_open() 2026-05-21 18:03:06 -04:00
trace_sched_switch.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
trace_sched_wakeup.c tracing: Allow tracer to add more than 32 options 2025-11-04 21:44:00 +09:00
trace_selftest_dynamic.c
trace_selftest.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
trace_seq.c tracing: Add bitmask-list option for human-readable bitmask display 2026-01-26 17:00:50 -05:00
trace_snapshot.c tracing: Remove duplicate latency_fsnotify() stub 2026-03-31 14:58:39 -04:00
trace_stack.c tracing updates for v6.16: 2025-05-29 21:04:36 -07:00
trace_stat.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
trace_stat.h
trace_synth.h
trace_syscalls.c bpf: Add sleepable support for classic tracepoint programs 2026-04-22 22:44:29 +02:00
trace_uprobe.c tracing: Replace BUG_ON with lockdep_assert_held in uprobe_buffer functions 2026-06-01 23:35:21 +09:00
trace.c ring-buffer: Updates for v7.2: 2026-06-18 21:23:22 -07:00
trace.h tracing updates for v7.1: 2026-04-17 09:43:12 -07:00
tracing_map.c tracing: Simplify pages allocation for tracing_map logic 2026-05-21 18:12:10 -04:00
tracing_map.h tracing: Simplify pages allocation for tracing_map logic 2026-05-21 18:12:10 -04:00
undefsyms_base.c tracing: Make undefsyms_base.c a first-class citizen 2026-04-22 11:24:41 -04:00