linux-kernel - [PATCH] drivers/base: kmemleak ignore a known leak

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Message-Id: <1543504357-4873-1-git-send-email-cai@gmx.us>
Date:   Thu, 29 Nov 2018 10:12:37 -0500
From:   Qian Cai <cai@....us>
To:     gregkh@...uxfoundation.org, rafael@...nel.org
Cc:     linux-kernel@...r.kernel.org, Qian Cai <cai@....us>
Subject: [PATCH] drivers/base: kmemleak ignore a known leak

unreferenced object 0xffff808ec6dc5a80 (size 128):
  comm "swapper/0", pid 1, jiffies 4294938063 (age 2560.530s)
  hex dump (first 32 bytes):
    ff ff ff ff 00 00 00 00 6b 6b 6b 6b 6b 6b 6b 6b  ........kkkkkkkk
    6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
  backtrace:
    [<00000000476dcf8c>] kmem_cache_alloc_trace+0x430/0x500
    [<000000004f708d37>] platform_device_register_full+0xbc/0x1e8
    [<000000006c2a7ec7>] acpi_create_platform_device+0x370/0x450
    [<00000000ef135642>] acpi_default_enumeration+0x34/0x78
    [<000000003bd9a052>] acpi_bus_attach+0x2dc/0x3e0
    [<000000003cf4f7f2>] acpi_bus_attach+0x108/0x3e0
    [<000000003cf4f7f2>] acpi_bus_attach+0x108/0x3e0
    [<000000002968643e>] acpi_bus_scan+0xb0/0x110
    [<0000000010dd0bd7>] acpi_scan_init+0x1a8/0x410
    [<00000000965b3c5a>] acpi_init+0x408/0x49c
    [<00000000ed4b9fe2>] do_one_initcall+0x178/0x7f4
    [<00000000a5ac5a74>] kernel_init_freeable+0x9d4/0xa9c
    [<0000000070ea6c15>] kernel_init+0x18/0x138
    [<00000000fb8fff06>] ret_from_fork+0x10/0x1c
    [<0000000041273a0d>] 0xffffffffffffffff

Then, faddr2line pointed out this line,

/*
 * This memory isn't freed when the device is put,
 * I don't have a nice idea for that though.  Conceptually
 * dma_mask in struct device should not be a pointer.
 * See http://thread.gmane.org/gmane.linux.kernel.pci/9081
 */
pdev->dev.dma_mask =
	kmalloc(sizeof(*pdev->dev.dma_mask), GFP_KERNEL);

Since this leak has been existed for more than 8-year now and it does not
reference other part of the memory, let kmemleak ignore it, so users don't
need to waste time reporting this in the future.

Signed-off-by: Qian Cai <cai@....us>
---
 drivers/base/platform.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index 41b91af..3e1587d 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -26,6 +26,7 @@
 #include <linux/clk/clk-conf.h>
 #include <linux/limits.h>
 #include <linux/property.h>
+#include <linux/kmemleak.h>
 
 #include "base.h"
 #include "power/power.h"
@@ -525,6 +526,8 @@ struct platform_device *platform_device_register_full(
 		if (!pdev->dev.dma_mask)
 			goto err;
 
+		kmemleak_ignore(pdev->dev.dma_mask);
+
 		*pdev->dev.dma_mask = pdevinfo->dma_mask;
 		pdev->dev.coherent_dma_mask = pdevinfo->dma_mask;
 	}
-- 
1.8.3.1