Re: v5.12-rc4 slab-out-of-bounds in xdr_set_page_base

["bfields@fieldses.org" <bfields@fieldses.org>]

On Mon, Apr 05, 2021 at 01:52:51PM +0000, Trond Myklebust wrote:
> On Mon, 2021-04-05 at 09:44 -0400, J. Bruce Fields wrote:
> > I'm getting the following on an NFS client under testing, is it
> > anything
> > known?
> > 
> > Not sure yet exactly which test is triggering it or when it started
> > happening; I'll follow up when I figure that out.
> > 
> 
> I'd be unsurprised to find that there may still be a couple of residual
> bugs in read plus (and I'm not willing to spend much more time
> debugging it).
> 
> Are you seeing this when using ordinary reads too?

Experimenting some more....

I see it reliably over 4.2, but not over 4.1.  So, yes, it's probably
READ_PLUS.

I can reproduce with just cthon basic tests.

--b.

> 
> > --b.
> > 
> > [ 1001.688041]
> > ==================================================================
> > [ 1001.689529] BUG: KASAN: slab-out-of-bounds in
> > xdr_set_page_base+0x339/0x350 [sunrpc]
> > [ 1001.691017] Read of size 8 at addr ffff88800dd8fe80 by task
> > kworker/u4:1/25
> > 
> > [ 1001.692517] CPU: 0 PID: 25 Comm: kworker/u4:1 Not tainted 5.12.0-
> > rc4-45853-g62007e38c8d6 #3177
> > [ 1001.694121] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009),
> > BIOS 1.14.0-1.fc33 04/01/2014
> > [ 1001.695676] Workqueue: rpciod rpc_async_schedule [sunrpc]
> > [ 1001.696776] Call Trace:
> > [ 1001.697176]  dump_stack+0x93/0xc2
> > [ 1001.697762]  print_address_description.constprop.0+0x18/0x110
> > [ 1001.698511]  ? xdr_set_page_base+0x339/0x350 [sunrpc]
> > [ 1001.699216]  ? xdr_set_page_base+0x339/0x350 [sunrpc]
> > [ 1001.700665]  kasan_report.cold+0x7c/0xd8
> > [ 1001.701420]  ? xdr_set_page_base+0x339/0x350 [sunrpc]
> > [ 1001.702379]  xdr_set_page_base+0x339/0x350 [sunrpc]
> > [ 1001.703273]  xdr_align_data+0x6e9/0xe60 [sunrpc]
> > [ 1001.703967]  ? __decode_op_hdr+0x24/0x4d0 [nfsv4]
> > [ 1001.704665]  nfs4_xdr_dec_read_plus+0x40d/0x780 [nfsv4]
> > [ 1001.705371]  ? nfs4_xdr_dec_offload_cancel+0x160/0x160 [nfsv4]
> > [ 1001.706165]  ? lock_is_held_type+0xd5/0x130
> > [ 1001.706702]  gss_unwrap_resp+0x145/0x220 [auth_rpcgss]
> > [ 1001.707355]  call_decode+0x5d2/0x830 [sunrpc]
> > [ 1001.707954]  ? rpc_decode_header+0x17c0/0x17c0 [sunrpc]
> > [ 1001.708739]  ? lock_is_held_type+0xd5/0x130
> > [ 1001.709268]  ? rpc_decode_header+0x17c0/0x17c0 [sunrpc]
> > [ 1001.709974]  __rpc_execute+0x1b8/0xda0 [sunrpc]
> > [ 1001.710581]  ? rpc_exit+0xb0/0xb0 [sunrpc]
> > [ 1001.711146]  ? lock_downgrade+0x6a0/0x6a0
> > [ 1001.711662]  rpc_async_schedule+0x9f/0x140 [sunrpc]
> > [ 1001.712355]  process_one_work+0x7ac/0x12d0
> > [ 1001.712903]  ? lock_release+0x6d0/0x6d0
> > [ 1001.713386]  ? queue_delayed_work_on+0x80/0x80
> > [ 1001.713986]  ? rwlock_bug.part.0+0x90/0x90
> > [ 1001.714507]  worker_thread+0x590/0xf80
> > [ 1001.714995]  ? rescuer_thread+0xb80/0xb80
> > [ 1001.715504]  kthread+0x375/0x450
> > [ 1001.715913]  ? _raw_spin_unlock_irq+0x24/0x50
> > [ 1001.716518]  ? kthread_create_worker_on_cpu+0xb0/0xb0
> > [ 1001.717161]  ret_from_fork+0x22/0x30
> > 
> > [ 1001.717855] Allocated by task 9075:
> > [ 1001.718291]  kasan_save_stack+0x1b/0x40
> > [ 1001.718778]  __kasan_kmalloc+0x78/0x90
> > [ 1001.719250]  __kmalloc+0x112/0x210
> > [ 1001.719679]  nfs_generic_pgio+0x99f/0xe80 [nfs]
> > [ 1001.720319]  nfs_generic_pg_pgios+0xea/0x3f0 [nfs]
> > [ 1001.720937]  nfs_pageio_doio+0x10b/0x2b0 [nfs]
> > [ 1001.721540]  nfs_pageio_complete+0x19d/0x550 [nfs]
> > [ 1001.722161]  nfs_pageio_complete_read+0x14/0x180 [nfs]
> > [ 1001.722823]  nfs_readpages+0x313/0x440 [nfs]
> > [ 1001.723372]  read_pages+0x4ab/0xa40
> > [ 1001.723816]  page_cache_ra_unbounded+0x361/0x620
> > [ 1001.724442]  filemap_get_pages+0x631/0xf60
> > [ 1001.724959]  filemap_read+0x24d/0x840
> > [ 1001.725425]  nfs_file_read+0x144/0x240 [nfs]
> > [ 1001.726031]  new_sync_read+0x352/0x5d0
> > [ 1001.726503]  vfs_read+0x202/0x3f0
> > [ 1001.726926]  ksys_read+0xe9/0x1b0
> > [ 1001.727341]  do_syscall_64+0x33/0x40
> > [ 1001.727797]  entry_SYSCALL_64_after_hwframe+0x44/0xae
> > 
> > [ 1001.728671] The buggy address belongs to the object at
> > ffff88800dd8fe00
> >                 which belongs to the cache kmalloc-128 of size 128
> > [ 1001.730853] The buggy address is located 0 bytes to the right of
> >                 128-byte region [ffff88800dd8fe00, ffff88800dd8fe80)
> > [ 1001.732830] The buggy address belongs to the page:
> > [ 1001.733549] page:000000009a9ea03c refcount:1 mapcount:0
> > mapping:0000000000000000 index:0x0 pfn:0xdd8f
> > [ 1001.734754] flags: 0x4000000000000200(slab)
> > [ 1001.735282] raw: 4000000000000200 ffffea00002c16a8
> > ffffea00001b27e8 ffff888007040400
> > [ 1001.736285] raw: 0000000000000000 ffff88800dd8f000
> > 0000000100000010
> > [ 1001.737064] page dumped because: kasan: bad access detected
> > 
> > [ 1001.737981] Memory state around the buggy address:
> > [ 1001.738579]  ffff88800dd8fd80: fc fc fc fc fc fc fc fc fc fc fc fc
> > fc fc fc fc
> > [ 1001.739475]  ffff88800dd8fe00: 00 00 00 00 00 00 00 00 00 00 00 00
> > 00 00 00 00
> > [ 1001.740411] >ffff88800dd8fe80: fc fc fc fc fc fc fc fc fc fc fc fc
> > fc fc fc fc
> > [ 1001.741331]                    ^
> > [ 1001.741795]  ffff88800dd8ff00: fa fb fb fb fb fb fb fb fb fb fb fb
> > fb fb fb fb
> > [ 1001.742693]  ffff88800dd8ff80: fc fc fc fc fc fc fc fc fc fc fc fc
> > fc fc fc fc
> > [ 1001.743589]
> > ==================================================================
> > 
> 
> -- 
> Trond Myklebust
> Linux NFS client maintainer, Hammerspace
> trond.myklebust@hammerspace.com
> 
>