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

From: Benjamin Coddington
Date: Fri Jun 17 2016 - 09:38:29 EST


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@xxxxxxxxxx> wrote:
Adding linux-nfs@xxxxxxxxxxxxxxx ..

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