From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: 2.6.28-rc1: EIP: slab_destroy+0x84/0x142 From: Matt Mackall In-Reply-To: <20081025025408.GA27684@x200.localdomain> References: <20081024185952.GA18526@x200.localdomain> <1224884318.3248.54.camel@calx> <20081024220750.GA22973@x200.localdomain> <20081025002406.GA20024@x200.localdomain> <20081025025408.GA27684@x200.localdomain> Content-Type: text/plain Date: Fri, 24 Oct 2008 22:00:45 -0500 Message-Id: <1224903645.3248.106.camel@calx> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Alexey Dobriyan Cc: Christoph Lameter , Linus Torvalds , linux-mm@kvack.org, penberg@cs.helsinki.fi, akpm@linux-foundation.org, avi@qumranet.com List-ID: On Sat, 2008-10-25 at 06:54 +0400, Alexey Dobriyan wrote: > On Sat, Oct 25, 2008 at 04:24:06AM +0400, Alexey Dobriyan wrote: > > On Fri, Oct 24, 2008 at 06:29:47PM -0500, Christoph Lameter wrote: > > > On Sat, 25 Oct 2008, Alexey Dobriyan wrote: > > > > > >> Fault occured at slab_destroy in KVM guest kernel. > > > > > > Please switch on all SLAB debug options and rerun. > > > > They're already on! > > > > New knowledge: turning off just DEBUG_PAGEALLOC makes oops dissapear, > > other debugging options don't matter. > > Here is typical scenario: > cache -- filp or dentry, ->buffer_size = 4096, objp = c643d000, dbg_redzone1 = c643df78. > > Unable to handle ... at c643df7c. which is not next page. Huh. That sounds more like an actual use-after-free. Possible that the object is getting freed twice? There's a call to kernel_map_pages(..., 0) on line 2905 of slab.c. Commenting it out will nullify the debugging effect of DEBUG_PAGEALLOC without changing the layout decisions and other behavior. If that kernel works, that probably means your oops is a genuine use-after-free. -- Mathematics is the supreme nostalgia of our time. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org