linux-kernel - re: slab error in verify_redzone

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Date:	Thu, 29 Jan 2009 14:55:32 -0800
From:	Andrew Vasquez <andrew.vasquez@...gic.com>
To:	Matthew Wilcox <matthew@....cx>
Cc:	Greg Kroah-Hartman <gregkh@...e.de>,
	Linux SCSI Mailing List <linux-scsi@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Seokmann Ju <seokmann.ju@...gic.com>
Subject: re: slab error in verify_redzone_free() badness...

Matthew,

During some NPIV regression tests with .29-rc3, we are seeing some
slab-corruption during vport tear-down:

	# create vport off fc-host1
	$ echo "2001567890abcdab:2001ef12345678ab" > /sys/class/fc_host/host1/vport_create
	# delete vport
	$ echo "2001567890abcdab:2001ef12345678ab" > /sys/class/fc_host/host1/vport_delete

Here's the backtrace:

	[  263.337035] slab error in verify_redzone_free(): cache `size-2048': memory outside object was overwritten
	[  263.340213] Pid: 7623, comm: bash Tainted: G   M       2.6.28 #32
	[  263.340213] Call Trace:
	[  263.340213]  [<ffffffff8027afd7>] __slab_error+0x1c/0x25
	[  263.340213]  [<ffffffff8027b43b>] cache_free_debugcheck+0x165/0x210
	[  263.340213]  [<ffffffff8027b672>] kfree+0x6b/0xc3
	[  263.340213]  [<ffffffff803947bb>] device_release+0x1a/0x6a
	[  263.340213]  [<ffffffff8032db9c>] kobject_release+0x33/0x63
	[  263.340213]  [<ffffffff8032db69>] kobject_release+0x0/0x63
	[  263.340213]  [<ffffffff8032e98e>] kref_put+0x32/0x6c
	[  263.340213]  [<ffffffffa002b73b>] qla24xx_vport_delete+0xc7/0x14f [qla2xxx]
	[  263.340213]  [<ffffffffa000061c>] fc_vport_terminate+0x81/0x1bb [scsi_transport_fc]
	[  263.340213]  [<ffffffffa0002a67>] store_fc_host_vport_delete+0x111/0x121 [scsi_transport_fc]
	[  263.340213]  [<ffffffff802bebea>] sysfs_write_file+0xb3/0x114
	[  263.340213]  [<ffffffff802803a3>] vfs_write+0xac/0x147
	[  263.340213]  [<ffffffff80280921>] sys_write+0x45/0x73
	[  263.340213]  [<ffffffff8020b45b>] system_call_fastpath+0x16/0x1b
	[  263.340213] ffff88007ddaad98: redzone 1:0xd84156c5635688c0, redzone 2:0x0.

We've bisected the problem down to:

	commit 210272a28465a7a31bcd580d2f9529f924965aa5
	Author: Matthew Wilcox <matthew@....cx>
	Date:   Thu Oct 16 14:57:54 2008 -0600

	    driver core: Remove completion from struct klist_node

	    Removing the completion from klist_node reduces its size from 64 bytes
	    to 28 on x86-64.  To maintain the semantics of klist_remove(), we add
	    a single list of klist nodes which are pending deletion and scan them.

	    Signed-off-by: Matthew Wilcox <willy@...ux.intel.com>
	    Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

At first glance the changes look fairly straight-forward...  Reverting
the problem commit (currently off .29-rc3) appears to clean up the
slab-badness.

Thoughts?

--
av
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