Re: V3.10-rc1 memory leak

[Catalin Marinas <catalin.marinas@arm.com>]

On Wed, May 15, 2013 at 04:15:46AM +0100, Larry Finger wrote:
> I do not see that particular one; however, I see 4 instances of
> 
> unreferenced object 0xffff8800b7979750 (size 8):
>    comm "swapper/0", pid 1, jiffies 4294892402 (age 21888.316s)
>    hex dump (first 8 bytes):
>      31 38 00 b7 00 88 ff ff                          18......
>    backtrace:
>      [<ffffffff81432ea1>] kmemleak_alloc+0x21/0x50
>      [<ffffffff81145d50>] __kmalloc_track_caller+0x140/0x2b0
>      [<ffffffff81119fb5>] kstrdup+0x35/0x70
>      [<ffffffff8125febc>] acpi_set_pnp_ids+0xd0/0x304
>      [<ffffffff81260c47>] acpi_scan_init_hotplug+0x47/0xa1
>      [<ffffffff81261223>] acpi_bus_check_add+0x66/0xd7
>      [<ffffffff8127877a>] acpi_ns_walk_namespace+0xb9/0x173
>      [<ffffffff81278bf3>] acpi_walk_namespace+0x93/0xc6
>      [<ffffffff812612dc>] acpi_bus_scan+0x48/0x9a
>      [<ffffffff818c983d>] acpi_scan_init+0x57/0x14b
>      [<ffffffff818c966a>] acpi_init+0x244/0x286
>      [<ffffffff810002fa>] do_one_initcall+0x10a/0x160
>      [<ffffffff8189cef0>] kernel_init_freeable+0x103/0x192
>      [<ffffffff814313a9>] kernel_init+0x9/0xf0
>      [<ffffffff8144992c>] ret_from_fork+0x7c/0xb0
>      [<ffffffffffffffff>] 0xffffffffffffffff
> 
> All four were allocated early in the bootup, and are the only leaks reported in 
> my system. I have not yet tested to see if they are false.

This looks to me like a real leak, possibly introduced by commit
6b772e8f9 (ACPI: Update PNPID match handling for notify). The
acpi_scan_init_hotplug() function calls acpi_set_pnp_ids() which
allocates pnp.unique_id (kstrdup()) but for some reason it fails and
does not set pnp.type.hardware_id. The return does not call
acpi_free_pnp_ids() which would be responsible for such freeing.
Something like below, but not tested and may fail some NULL pointer
checks:

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index fe158fd..c1bc608 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -1785,7 +1785,7 @@ static void acpi_scan_init_hotplug(acpi_handle handle, int type)
 	acpi_set_pnp_ids(handle, &pnp, type);
 
 	if (!pnp.type.hardware_id)
-		return;
+		goto out;
 
 	/*
 	 * This relies on the fact that acpi_install_notify_handler() will not
@@ -1800,6 +1800,7 @@ static void acpi_scan_init_hotplug(acpi_handle handle, int type)
 		}
 	}
 
+out:
 	acpi_free_pnp_ids(&pnp);
 }