linux-kernel - [PATCH] tracing: Fix memory leak in fgraph storage selftest

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Message-Id: <172411539857.28895.13119957560263401102.stgit@devnote2>
Date: Tue, 20 Aug 2024 09:56:38 +0900
From: "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org,
	mhiramat@...nel.org
Subject: [PATCH] tracing: Fix memory leak in fgraph storage selftest

From: Masami Hiramatsu (Google) <mhiramat@...nel.org>

With ftrace boot-time selftest, kmemleak reported some memory leaks in
the new test case for function graph storage for multiple tracers.

unreferenced object 0xffff888005060080 (size 32):
  comm "swapper/0", pid 1, jiffies 4294676440
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 20 10 06 05 80 88 ff ff  ........ .......
    54 0c 1e 81 ff ff ff ff 00 00 00 00 00 00 00 00  T...............
  backtrace (crc 7c93416c):
    [<000000000238ee6f>] __kmalloc_cache_noprof+0x11f/0x2a0
    [<0000000033d2b6c5>] enter_record+0xe8/0x150
    [<0000000054c38424>] match_records+0x1cd/0x230
    [<00000000c775b63d>] ftrace_set_hash+0xff/0x380
    [<000000007bf7208c>] ftrace_set_filter+0x70/0x90
    [<00000000a5c08dda>] test_graph_storage_multi+0x2e/0xf0
    [<000000006ba028ca>] trace_selftest_startup_function_graph+0x1e8/0x260
    [<00000000a715d3eb>] run_tracer_selftest+0x111/0x190
    [<00000000395cbf90>] register_tracer+0xdf/0x1f0
    [<0000000093e67f7b>] do_one_initcall+0x141/0x3b0
    [<00000000c591b682>] do_initcall_level+0x82/0xa0
    [<000000004e4c6600>] do_initcalls+0x43/0x70
    [<0000000034f3c4e4>] kernel_init_freeable+0x170/0x1f0
    [<00000000c7a5dab2>] kernel_init+0x1a/0x1a0
    [<00000000ea105947>] ret_from_fork+0x3a/0x50
    [<00000000a1932e84>] ret_from_fork_asm+0x1a/0x30
...

This means filter hash allocated for the fixtures are not correctly
released after the test.

Free those hash lists after tests are done and split the loop for
initialize fixture and register fixture for rollback.

Fixes: dd120af2d5f8 ("ftrace: Add multiple fgraph storage selftest")
Cc: stable@...r.kernel.org
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
---
 kernel/trace/trace_selftest.c |   23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c
index 97f1e4bc47dc..c4ad7cd7e778 100644
--- a/kernel/trace/trace_selftest.c
+++ b/kernel/trace/trace_selftest.c
@@ -942,7 +942,7 @@ static __init int test_graph_storage_multi(void)
 {
 	struct fgraph_fixture *fixture;
 	bool printed = false;
-	int i, ret;
+	int i, j, ret;
 
 	pr_cont("PASSED\n");
 	pr_info("Testing multiple fgraph storage on a function: ");
@@ -953,22 +953,35 @@ static __init int test_graph_storage_multi(void)
 		if (ret && ret != -ENODEV) {
 			pr_cont("*Could not set filter* ");
 			printed = true;
-			goto out;
+			goto out2;
 		}
+	}
 
+	for (j = 0; j < ARRAY_SIZE(store_bytes); j++) {
+		fixture = &store_bytes[j];
 		ret = register_ftrace_graph(&fixture->gops);
 		if (ret) {
 			pr_warn("Failed to init store_bytes fgraph tracing\n");
 			printed = true;
-			goto out;
+			goto out1;
 		}
 	}
 
 	DYN_FTRACE_TEST_NAME();
-out:
+out1:
+	while (--j >= 0) {
+		fixture = &store_bytes[j];
+		unregister_ftrace_graph(&fixture->gops);
+
+		if (fixture->error_str && !printed) {
+			pr_cont("*** %s ***", fixture->error_str);
+			printed = true;
+		}
+	}
+out2:
 	while (--i >= 0) {
 		fixture = &store_bytes[i];
-		unregister_ftrace_graph(&fixture->gops);
+		ftrace_free_filter(&fixture->gops.ops);
 
 		if (fixture->error_str && !printed) {
 			pr_cont("*** %s ***", fixture->error_str);