[PATCH v2] of: Fix unbalanced of node refcount and memory leaks

From: Jinjie Ruan
Date: Tue Oct 08 2024 - 21:50:51 EST

Got following report when doing overlay_test:

OF: ERROR: memory leak, expected refcount 1 instead of 2,
of_node_get()/of_node_put() unbalanced - destroy cset entry:
attach overlay node /kunit-test

OF: ERROR: memory leak before free overlay changeset, /kunit-test

In of_overlay_apply_kunit_cleanup(), the "np" will be overwritten by the
second of_find_node_by_name(), and the error message came from
kunit_cleanup(), just call of_node_put() before it to fix it.

It also fix the following memory leaks:

unreferenced object 0xffffff80c7d22800 (size 256):
comm "kunit_try_catch", pid 236, jiffies 4294894764
hex dump (first 32 bytes):
d0 26 d4 c2 80 ff ff ff 00 00 00 00 00 00 00 00 .&..............
60 19 75 c1 80 ff ff ff 00 00 00 00 00 00 00 00 `.u.............
backtrace (crc ee0a471c):
[<0000000058ea1340>] kmemleak_alloc+0x34/0x40
[<00000000c538ac7e>] __kmalloc_cache_noprof+0x26c/0x2f4
[<00000000119f34f3>] __of_node_dup+0x4c/0x328
[<00000000b212ca39>] build_changeset_next_level+0x2cc/0x4c0
[<00000000eb208e87>] of_overlay_fdt_apply+0x930/0x1334
[<000000005bdc53a3>] of_overlay_fdt_apply_kunit+0x54/0x10c
[<00000000143acd5d>] of_overlay_apply_kunit_cleanup+0x12c/0x524
[<00000000a813abc8>] kunit_try_run_case+0x13c/0x3ac
[<00000000d77ab00c>] kunit_generic_run_threadfn_adapter+0x80/0xec
[<000000000b296be1>] kthread+0x2e8/0x374
[<0000000007bd1c51>] ret_from_fork+0x10/0x20
unreferenced object 0xffffff80c1751960 (size 16):
comm "kunit_try_catch", pid 236, jiffies 4294894764
hex dump (first 16 bytes):
6b 75 6e 69 74 2d 74 65 73 74 00 c1 80 ff ff ff kunit-test......
backtrace (crc 18196259):
[<0000000058ea1340>] kmemleak_alloc+0x34/0x40
[<0000000071006e2c>] __kmalloc_node_track_caller_noprof+0x300/0x3e0
[<00000000b16ac6cb>] kstrdup+0x48/0x84
[<0000000050e3373b>] __of_node_dup+0x60/0x328
[<00000000b212ca39>] build_changeset_next_level+0x2cc/0x4c0
[<00000000eb208e87>] of_overlay_fdt_apply+0x930/0x1334
[<000000005bdc53a3>] of_overlay_fdt_apply_kunit+0x54/0x10c
[<00000000143acd5d>] of_overlay_apply_kunit_cleanup+0x12c/0x524
[<00000000a813abc8>] kunit_try_run_case+0x13c/0x3ac
[<00000000d77ab00c>] kunit_generic_run_threadfn_adapter+0x80/0xec
[<000000000b296be1>] kthread+0x2e8/0x374
[<0000000007bd1c51>] ret_from_fork+0x10/0x20
unreferenced object 0xffffff80c2e96e00 (size 192):
comm "kunit_try_catch", pid 236, jiffies 4294894764
hex dump (first 32 bytes):
80 19 75 c1 80 ff ff ff 0b 00 00 00 00 00 00 00 ..u.............
a0 19 75 c1 80 ff ff ff 00 6f e9 c2 80 ff ff ff ..u......o......
backtrace (crc 1924cba4):
[<0000000058ea1340>] kmemleak_alloc+0x34/0x40
[<00000000c538ac7e>] __kmalloc_cache_noprof+0x26c/0x2f4
[<000000009fdd35ad>] __of_prop_dup+0x7c/0x2ec
[<00000000aa4e0111>] add_changeset_property+0x548/0x9e0
[<000000004777e25b>] build_changeset_next_level+0xd4/0x4c0
[<00000000a9c93f8a>] build_changeset_next_level+0x3a8/0x4c0
[<00000000eb208e87>] of_overlay_fdt_apply+0x930/0x1334
[<000000005bdc53a3>] of_overlay_fdt_apply_kunit+0x54/0x10c
[<00000000143acd5d>] of_overlay_apply_kunit_cleanup+0x12c/0x524
[<00000000a813abc8>] kunit_try_run_case+0x13c/0x3ac
[<00000000d77ab00c>] kunit_generic_run_threadfn_adapter+0x80/0xec
[<000000000b296be1>] kthread+0x2e8/0x374
[<0000000007bd1c51>] ret_from_fork+0x10/0x20
unreferenced object 0xffffff80c1751980 (size 16):
comm "kunit_try_catch", pid 236, jiffies 4294894764
hex dump (first 16 bytes):
63 6f 6d 70 61 74 69 62 6c 65 00 c1 80 ff ff ff compatible......
backtrace (crc 42df3c87):
[<0000000058ea1340>] kmemleak_alloc+0x34/0x40
[<0000000071006e2c>] __kmalloc_node_track_caller_noprof+0x300/0x3e0
[<00000000b16ac6cb>] kstrdup+0x48/0x84
[<00000000a8888fd8>] __of_prop_dup+0xb0/0x2ec
[<00000000aa4e0111>] add_changeset_property+0x548/0x9e0
[<000000004777e25b>] build_changeset_next_level+0xd4/0x4c0
[<00000000a9c93f8a>] build_changeset_next_level+0x3a8/0x4c0
[<00000000eb208e87>] of_overlay_fdt_apply+0x930/0x1334
[<000000005bdc53a3>] of_overlay_fdt_apply_kunit+0x54/0x10c
[<00000000143acd5d>] of_overlay_apply_kunit_cleanup+0x12c/0x524
[<00000000a813abc8>] kunit_try_run_case+0x13c/0x3ac
[<00000000d77ab00c>] kunit_generic_run_threadfn_adapter+0x80/0xec
[<000000000b296be1>] kthread+0x2e8/0x374
unreferenced object 0xffffff80c2e96f00 (size 192):
comm "kunit_try_catch", pid 236, jiffies 4294894764
hex dump (first 32 bytes):
40 f7 bb c6 80 ff ff ff 0b 00 00 00 00 00 00 00 @...............
c0 19 75 c1 80 ff ff ff 00 00 00 00 00 00 00 00 ..u.............
backtrace (crc f2f57ea7):
[<0000000058ea1340>] kmemleak_alloc+0x34/0x40
[<00000000c538ac7e>] __kmalloc_cache_noprof+0x26c/0x2f4
[<000000009fdd35ad>] __of_prop_dup+0x7c/0x2ec
[<00000000aa4e0111>] add_changeset_property+0x548/0x9e0
[<000000004777e25b>] build_changeset_next_level+0xd4/0x4c0
[<00000000a9c93f8a>] build_changeset_next_level+0x3a8/0x4c0
[<00000000eb208e87>] of_overlay_fdt_apply+0x930/0x1334
[<000000005bdc53a3>] of_overlay_fdt_apply_kunit+0x54/0x10c
[<00000000143acd5d>] of_overlay_apply_kunit_cleanup+0x12c/0x524
[<00000000a813abc8>] kunit_try_run_case+0x13c/0x3ac
[<00000000d77ab00c>] kunit_generic_run_threadfn_adapter+0x80/0xec
[<000000000b296be1>] kthread+0x2e8/0x374
[<0000000007bd1c51>] ret_from_fork+0x10/0x20
......

How to reproduce:
CONFIG_OF_OVERLAY_KUNIT_TEST=y, CONFIG_DEBUG_KMEMLEAK=y
and CONFIG_DEBUG_KMEMLEAK_AUTO_SCAN=y, launch the kernel.

Fixes: 5c9dd72d8385 ("of: Add a KUnit test for overlays and test managed APIs")
Signed-off-by: Jinjie Ruan <ruanjinjie@xxxxxxxxxx>
---
v2:
- Add memory leak stack.
- Update the commit message.
---
drivers/of/overlay_test.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/of/overlay_test.c b/drivers/of/overlay_test.c
index 19a292cdeee3..e95b1152612c 100644
--- a/drivers/of/overlay_test.c
+++ b/drivers/of/overlay_test.c
@@ -73,12 +73,12 @@ static void of_overlay_apply_kunit_cleanup(struct kunit *test)

np = of_find_node_by_name(NULL, kunit_node_name);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, np);
- of_node_put_kunit(test, np);

pdev = of_find_device_by_node(np);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, pdev);
put_device(&pdev->dev); /* Not derefing 'pdev' after this */

+ of_node_put(np);
/* Remove overlay */
kunit_cleanup(&fake);

--
2.34.1