From: "Steven Rostedt (Google)" rostedt@goodmis.org

When a tracing instance is removed, the error messages that hold errors that occurred in the instance needs to be freed. The following reports a memory leak:

# cd /sys/kernel/tracing # mkdir instances/foo # echo 'hist:keys=x' > instances/foo/events/sched/sched_switch/trigger # cat instances/foo/error_log [ 117.404795] hist:sched:sched_switch: error: Couldn't find field Command: hist:keys=x ^ # rmdir instances/foo

Then check for memory leaks:

# echo scan > /sys/kernel/debug/kmemleak # cat /sys/kernel/debug/kmemleak unreferenced object 0xffff88810d8ec700 (size 192): comm "bash", pid 869, jiffies 4294950577 (age 215.752s) hex dump (first 32 bytes): 60 dd 68 61 81 88 ff ff 60 dd 68 61 81 88 ff ff `.ha....`.ha.... a0 30 8c 83 ff ff ff ff 26 00 0a 00 00 00 00 00 .0......&....... backtrace: [<00000000dae26536>] kmalloc_trace+0x2a/0xa0 [<00000000b2938940>] tracing_log_err+0x277/0x2e0 [<000000004a0e1b07>] parse_atom+0x966/0xb40 [<0000000023b24337>] parse_expr+0x5f3/0xdb0 [<00000000594ad074>] event_hist_trigger_parse+0x27f8/0x3560 [<00000000293a9645>] trigger_process_regex+0x135/0x1a0 [<000000005c22b4f2>] event_trigger_write+0x87/0xf0 [<000000002cadc509>] vfs_write+0x162/0x670 [<0000000059c3b9be>] ksys_write+0xca/0x170 [<00000000f1cddc00>] do_syscall_64+0x3e/0xc0 [<00000000868ac68c>] entry_SYSCALL_64_after_hwframe+0x72/0xdc unreferenced object 0xffff888170c35a00 (size 32): comm "bash", pid 869, jiffies 4294950577 (age 215.752s) hex dump (first 32 bytes): 0a 20 20 43 6f 6d 6d 61 6e 64 3a 20 68 69 73 74 . Command: hist 3a 6b 65 79 73 3d 78 0a 00 00 00 00 00 00 00 00 :keys=x......... backtrace: [<000000006a747de5>] __kmalloc+0x4d/0x160 [<000000000039df5f>] tracing_log_err+0x29b/0x2e0 [<000000004a0e1b07>] parse_atom+0x966/0xb40 [<0000000023b24337>] parse_expr+0x5f3/0xdb0 [<00000000594ad074>] event_hist_trigger_parse+0x27f8/0x3560 [<00000000293a9645>] trigger_process_regex+0x135/0x1a0 [<000000005c22b4f2>] event_trigger_write+0x87/0xf0 [<000000002cadc509>] vfs_write+0x162/0x670 [<0000000059c3b9be>] ksys_write+0xca/0x170 [<00000000f1cddc00>] do_syscall_64+0x3e/0xc0 [<00000000868ac68c>] entry_SYSCALL_64_after_hwframe+0x72/0xdc

The problem is that the error log needs to be freed when the instance is removed.

Link: https://lore.kernel.org/lkml/76134d9f-a5ba-6a0d-37b3-28310b4a1e91@alu.unizg.... Link: https://lore.kernel.org/linux-trace-kernel/20230404194504.5790b95f@gandalf.l...

Cc: stable@vger.kernel.org Cc: Masami Hiramatsu mhiramat@kernel.org Cc: Andrew Morton akpm@linux-foundation.org Cc: Mark Rutland mark.rutland@arm.com Cc: Thorsten Leemhuis regressions@leemhuis.info Cc: Ulf Hansson ulf.hansson@linaro.org Cc: Eric Biggers ebiggers@kernel.org Fixes: 2f754e771b1a6 ("tracing: Have the error logs show up in the proper instances") Reported-by: Mirsad Goran Todorovac mirsad.todorovac@alu.unizg.hr Tested-by: Mirsad Todorovac mirsad.todorovac@alu.unizg.hr Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org --- kernel/trace/trace.c | 1 + 1 file changed, 1 insertion(+)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 4686473b8497..36a6037823cd 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -9516,6 +9516,7 @@ static int __remove_instance(struct trace_array *tr) tracefs_remove(tr->dir); free_percpu(tr->last_func_repeats); free_trace_buffers(tr); + clear_tracing_err_log(tr);

for (i = 0; i < tr->nr_topts; i++) { kfree(tr->topts[i].topts);