netdev - Re: [PATCH 1/3] drivers/net/ipg.c: Fix skbuff leak

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Message-ID: <20080109003840.22917.qmail@science.horizon.com>
Date:	8 Jan 2008 19:38:40 -0500
From:	linux@...izon.com
To:	linux@...izon.com, romieu@...zoreil.com
Cc:	akpm@...ux-foundation.org, davem@...emloft.net,
	netdev@...r.kernel.org
Subject: Re: [PATCH 1/3] drivers/net/ipg.c: Fix skbuff leak

> Can you try the patch below ?

Testing now... (I presume you noticed the one-character typo in my
earlier patch.  That should be "mc = mc->next", not "mv = mc->next".)

That doesn't seem to do it.  Not entirely, at least.  After downloading
and partially re-uploading an 800M file, slabtop reports:

  OBJS ACTIVE  USE OBJ SIZE  SLABS OBJ/SLAB CACHE SIZE NAME
341576 341574  99%    0.50K  42697        8    170788K kmalloc-512
342006 341953  99%    0.19K  16286       21     65144K kmalloc-192
 30592  30575  99%    2.00K   7648        4     61184K kmalloc-2048
 30213  30193  99%    0.44K   3357        9     13428K skbuff_fclone_cache
  7650   7643  99%    0.08K    150       51       600K sysfs_dir_cache
  4000   3938  98%    0.12K    125       32       500K kmalloc-128
   258    258 100%    1.15K     43        6       344K raid5-md5
   232    221  95%    1.00K     58        4       232K kmalloc-1024
  3136   3110  99%    0.06K     49       64       196K kmalloc-64
   264     80  30%    0.68K     24       11       192K ext3_inode_cache

The "kmalloc-2048" was down in the noise before the upload started.
This is in single-user mode, after sync and echo 3 > /proc/sys/vm/drop_caches.

I'll have to try this after this evening's social plans, but I'm thinking
of implementing more rapid bug detection: explicitly zero the sp->TxBuff
slot when the skb is freed, and check that it is zero before putting
anything else in there.  (And likewise for RxBuff.)

That way, I don't have to use up a noticeable amount of memory to see
the bug and reboot to clear up the damage each test cycle.
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