linux-kernel - Re: slab-out-of-bounds in rpc/nfs

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Date:	Fri, 17 Jun 2016 09:38:48 -0400
From:	"Benjamin Coddington" <bcodding@...hat.com>
To:	"Calvin Owens" <calvinowens@...com>
Cc:	"Dmitry Vyukov" <dvyukov@...gle.com>,
	"Alexei Starovoitov" <alexei.starovoitov@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-nfs@...r.kernel.org
Subject: Re: slab-out-of-bounds in rpc/nfs

On 16 Jun 2016, at 13:52, Calvin Owens wrote:

> On Tuesday 03/08 at 11:37 +0100, Dmitry Vyukov wrote:
>> On Tue, Mar 8, 2016 at 11:27 AM, Benjamin Coddington
>> <bcodding@...hat.com> wrote:
>>> Adding linux-nfs@...r.kernel.org ..
>>>
>>> On Mon, 7 Mar 2016, Alexei Starovoitov wrote:
>>>
>>>> seeing on ton of these errors on net-next with kasan on.
>>>> Likely old bug though.
>>>>
>>>> [  373.705691] BUG: KASAN: slab-out-of-bounds in memcpy+0x28/0x40 
>>>> at
>>>> addr ffff8811ada62cb0
>>>> [  373.707137] Write of size 28 by task bash/7059
>>>> [  373.708177] 
>>>> =============================================================================
>>>> [  373.709711] BUG kmalloc-4096 (Tainted: G        W      ): kasan:
>>>> bad access detected
>>>> [  373.711185] 
>>>> -----------------------------------------------------------------------------
>>>> [  373.711185]
>>>> [  373.721461] INFO: Allocated in rpc_malloc+0x58/0xd0 age=21 cpu=5 
>>>> pid=7059
>>>> [  373.727158]     ___slab_alloc+0x4e2/0x500
>>>> [  373.728469]     __slab_alloc+0x43/0x70
>>>> [  373.729222]     __kmalloc+0x286/0x350
>>>> [  373.729978]     rpc_malloc+0x58/0xd0
>>>> [  373.730590]     call_allocate+0x333/0x690
>>>> [  373.731428]     __rpc_execute+0x187/0xad0
>>>> [  373.734395]     rpc_execute+0xe1/0x2c0
>>>> [  373.735020]     rpc_run_task+0x1ce/0x250
>>>> [  373.735706]     rpc_call_sync+0x93/0x150
>>>> [  373.736387]     nfs3_rpc_wrapper.constprop.12+0x9b/0x240
>>>> [  373.742818]     nfs3_proc_readdir+0x230/0x390
>>>> [  373.750157]     nfs_readdir_xdr_to_array+0x501/0x9b0
>>>> [  373.753520]     nfs_readdir_filler+0x68/0x160
>>>> [  373.758455]     do_read_cache_page+0x8c/0x3c0
>>>> [  373.761745]     read_cache_page+0x46/0x70
>>>> [  373.763269]     nfs_readdir+0x420/0x1380
>>>> [  373.764078] INFO: Freed in rpc_free+0x41/0x70 age=64 cpu=5 
>>>> pid=7059
>>>> [  373.765335]     __slab_free+0x175/0x280
>>>> [  373.766106]     kfree+0x25c/0x2a0
>>>> [  373.766809]     rpc_free+0x41/0x70
>>>> [  373.767629]     xprt_release+0x2c5/0x8f0
>>>> [  373.768430]     rpc_release_resources_task+0x14/0x80
>>>> [  373.769403]     __rpc_execute+0x547/0xad0
>>>> [  373.770249]     rpc_execute+0xe1/0x2c0
>>>> [  373.770995]     rpc_run_task+0x1ce/0x250
>>>> [  373.771786]     rpc_call_sync+0x93/0x150
>>>> [  373.772672]     nfs3_rpc_wrapper.constprop.12+0x9b/0x240
>>>> [  373.773704]     nfs3_proc_access+0x1f1/0x330
>>>> [  373.774544]     nfs_do_access+0x94f/0x12d0
>>>> [  373.775572]     nfs_permission+0x469/0x580
>>>> [  373.776465]     __inode_permission+0x151/0x230
>>>> [  373.780764]     inode_permission+0x21/0xf0
>>>> [  373.791392]     may_open+0x14b/0x260
>>>>
>>
>> The report misses the most interesting part -- the out-of-bounds
>> access stack. It should be at the bottom of the report. If you still
>> have the full report, please post it.
>
> I'm triggering this as well on 4.7-rc3. I can reproduce it as far back 
> as 4.0,
> can't easily test any further back because that's when KASAN was 
> merged.
>
> Logs and Kconfig follow. I can trigger this 100% of the time.

Hi Calvin, how are you triggering this?  I would guess this is getdents 
or a
readdir that's been signaled before the server replies..

Ben