linux-kernel - Memory leak in iwlwifi or false positive?

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Date:	Thu, 02 Jul 2009 22:32:03 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	linux-wireless@...r.kernel.org,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Memory leak in iwlwifi or false positive?

Hi,

I'm trying to get kmemleak more robust and with the latest patches (not
pushed yet) it seems to no longer show so many random leaks. However, I
get a lot of leaks reported in the iwlwifi code, about 4800 and they do
not disappear from any subsequent memory scanning (as is usually the
case with false positives). There are a lot of kmalloc's of < 512 bytes
and /proc/slabinfo seems to be in line with this:

kmalloc-512         5440   5481

This happens shortly after booting. Note that if an object is freed,
kmemleak no longer tracks it and therefore no reporting. But in this
case it looks like the iwlwifi code really allocated ~4800 blocks. Is it
normal for this code to keep so many blocks allocated? If yes, it is
probably kmemleak missing some root object in the references tree.

I'm not familiar with this code so any help is greatly appreciated.

The majority of kmemleak traces look like this:

unreferenced object 0xc1be3d40 (size 512):
  comm "iwlagn", pid 1571, jiffies 4294903229
  backtrace:
    [<c01e1f0b>] kmemleak_alloc+0x14b/0x290
    [<c01db2e5>] __kmalloc+0x125/0x1e0
    [<f95c77ef>] iwl_tx_queue_init+0x3f/0x310 [iwlcore]
    [<f95c9276>] iwl_txq_ctx_reset+0x206/0x5a0 [iwlcore]
    [<f95c199a>] iwl_hw_nic_init+0xba/0x110 [iwlcore]
    [<f9765263>] __iwl_up+0xb3/0x340 [iwlagn]
    [<f9765d72>] iwl_bg_up+0x32/0x50 [iwlagn]
    [<c0150d7d>] worker_thread+0x1ad/0x2d0
    [<c01555dc>] kthread+0x7c/0x90
    [<c0103cb7>] kernel_thread_helper+0x7/0x10
    [<ffffffff>] 0xffffffff

For a full kmemleak log and dmesg, see:

http://homepage.ntlworld.com/cmarinas/kmemleak-3
http://homepage.ntlworld.com/cmarinas/dmesg-3

Thanks.

-- 
Catalin

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