linux-kernel - Re: Redzone overwritten with CONFIG

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Message-ID: <20080527174738.GZ30402@sequoia.sous-sol.org>
Date:	Tue, 27 May 2008 10:47:38 -0700
From:	Chris Wright <chrisw@...s-sol.org>
To:	Pekka Enberg <penberg@...helsinki.fi>
Cc:	Eric Sesterhenn <snakebyte@....de>, linux-kernel@...r.kernel.org,
	Chris Wright <chrisw@...s-sol.org>,
	James Morris <jmorris@...ei.org>,
	William Lee Irwin III <wli@...omorphy.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Vegard Nossum <vegard.nossum@...il.com>
Subject: Re: Redzone overwritten with CONFIG_SECURITY

* Pekka Enberg (penberg@...helsinki.fi) wrote:
> On Mon, May 26, 2008 at 5:34 PM, Eric Sesterhenn <snakebyte@....de> wrote:
> > i enabled CONFIG_SECURITY on current git and get tons of
> > Redzone overwritten errors during early boot, even
> > with CONFIG_SECURITY_CAPABILITIES and CONFIG_SECURITY_NETWORK
> > disabled. After a while it ends with a kernel panic
> > saying: not syncing: Out of memory and no killable process...
> > Root partition is ext3 format.
> 
> So what kernel version is this and what's the last known version that
> worked? As it's early boot crash, maybe you can try to do git bisect
> on it?
> 
> >
> > At the moment i dont have a camera at hand, so i'll try
> > to write down everything which looks interesting, please tell
> > me if i missed something.
> >
> > The first 24 Bytes of the overwritten section contain
> > zeros. Then we have a constant 0x18, and three changing
> > values. the next three bites contain exactly the same
> > values, first the 0x18, then the two changing ones.
> >
> > The only value i found so far matching the 0x18 and
> > which might be related to CONFIG_SECURITY is CAP_SYS_RESOURCE
> > defined in /include/linux/capability.h
> >
> > BUG hugetlbfs_inode_cache: Redzone overwritten
> >
> > INFO: 0xccd8e250-0xccd8e253. First byte 0x0 instead of 0xbb
> > Info: Slab 0xc119d1c0 objects=12 used=0 fs=0xccd8e000 flags=0x400020c3
> > Info: Object 0xccd8e00 offset=0 fp=0xccd8e280
> >
> > Object 0xccd8e00: 00 00 00 ...
> > Object 0xccd8e10: 00 00 00 00 00 00 00 00 00 18 e0 d8 cc 18 e0 d8 cc
> > Object 0xccd8e20  00 00 00 ...

That looks like an addr within the object, like an INIT_LIST_HEAD.

> > Pid: 1, comm:swapper Not tainted 2.6.26-rc3-00436-gb373303 #42
> > print_trailer
> > check_bytes_and_report
> > check_object
> > __slab_alloc
> > kmem_cache_alloc
> > ? hugetlbfs_alloc_inode
> > ? hugetlbfs_alloc_inode
> > hugetlbfs_alloc_inode
> > alloc_inote
> > new_inode
> > hugetlbs_get_inote
> > hugetlbfs_fill_super
> > ? sget
> > ? set_anon_super
> > get_sb_node
> > hugetlbfs_get_sb
> > ? hugetlbfs_fill_super
> > vfs_kern_mount
> > kern_mount_data
> > init_hugetlbfs_fs
> > ? init_once
> > ? kernel_init
> > kernel_init

ok, do_init_calls time frame with that config...CONFIG_SECURITY isn't
really doing any allocations, nor much in the way of memory writes.
It would get called into via the:

 hugetlbs_get_inode
   new_inode
     alloc_inode
       security_inode_alloc <-- and that'd be basically a no-op

> > Config follows:

I couldn't recreate with that config.
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