[GIT PULL] Please pull NFS client changes for Linux 4.13

[GIT PULL] Please pull NFS client changes for Linux 4.13

[Anna Schumaker]

Hi Linus,

The following changes since commit 32c1431eea4881a6b17bd7c639315010aeefa452:

  Linux 4.12-rc5 (2017-06-11 16:48:20 -0700)

are available in the git repository at:

  git://git.linux-nfs.org/projects/anna/linux-nfs.git tags/nfs-for-4.13-1

for you to fetch changes up to b4f937cffa66b3d56eb8f586e620d0b223a281a3:

  NFS: Don't run wake_up_bit() when nobody is waiting... (2017-07-13 16:57:18 -0400)


Stable bugfixes:
- Fix -EACCESS on commit to DS handling
- Fix initialization of nfs_page_array->npages
- Only invalidate dentries that are actually invalid

Features:
- Enable NFSoRDMA transparent state migration
- Add support for lookup-by-filehandle
- Add support for nfs re-exporting

Other bugfixes and cleanups:
- Christoph cleaned up the way we declare NFS operations
- Clean up various internal structures
- Various cleanups to commits
- Various improvements to error handling
- Set the dt_type of . and .. entries in NFS v4
- Make slot allocation more reliable
- Fix fscache stat printing
- Fix uninitialized variable warnings
- Fix potential list overrun in nfs_atomic_open()
- Fix a race in NFSoRDMA RPC reply handler
- Fix return size for nfs42_proc_copy()
- Fix against MAC forgery timing attacks


As Bruce mentioned in his pull request, we didn't do a good job coordinating
with Christoph's patches from the beginning.  I ended up rebasing my tree on
top of Christoph's nfs-ops branch to prevent duplicate commits.  Apologies if
that was the wrong choice!

Cheers,
Anna

----------------------------------------------------------------
Anna Schumaker (1):
      NFS: Set FATTR4_WORD0_TYPE for . and .. entries

Benjamin Coddington (3):
      NFS: convert flags to bool
      NFS: nfs_rename() - revalidate directories on -ERESTARTSYS
      NFS: Fix initialization of nfs_page_array->npages

Christoph Hellwig (33):
      sunrpc: properly type argument to kxdreproc_t
      sunrpc: fix encoder callback prototypes
      lockd: fix encoder callback prototypes
      nfs: fix encoder callback prototypes
      nfsd: fix encoder callback prototypes
      sunrpc/auth_gss: nfsd: fix encoder callback prototypes
      sunrpc: properly type argument to kxdrdproc_t
      sunrpc: fix decoder callback prototypes
      sunrpc/auth_gss: fix decoder callback prototypes
      nfsd: fix decoder callback prototypes
      lockd: fix decoder callback prototypes
      nfs: fix decoder callback prototypes
      nfs: don't cast callback decode/proc/encode routines
      lockd: fix some weird indentation
      sunrpc: move p_count out of struct rpc_procinfo
      nfs: use ARRAY_SIZE() in the nfsacl_version3 declaration
      sunrpc: mark all struct rpc_procinfo instances as const
      nfsd4: const-ify nfs_cb_version4
      nfsd: use named initializers in PROC()
      nfsd: remove the unused PROC() macro in nfs3proc.c
      sunrpc: properly type pc_func callbacks
      sunrpc: properly type pc_release callbacks
      sunrpc: properly type pc_decode callbacks
      sunrpc: properly type pc_encode callbacks
      sunrpc: remove kxdrproc_t
      nfsd4: properly type op_set_currentstateid callbacks
      nfsd4: properly type op_get_currentstateid callbacks
      nfsd4: remove nfsd4op_rsize
      nfsd4: properly type op_func callbacks
      sunrpc: move pc_count out of struct svc_procinfo
      sunrpc: mark all struct svc_procinfo instances as const
      sunrpc: mark all struct svc_version instances as const
      nfsd4: const-ify nfsd4_ops

Chuck Lever (13):
      xprtrdma: On invalidation failure, remove MWs from rl_registered
      xprtrdma: Pre-mark remotely invalidated MRs
      xprtrdma: Pass only the list of registered MRs to ro_unmap_sync
      xprtrdma: Rename rpcrdma_req::rl_free
      xprtrdma: Fix client lock-up after application signal fires
      xprtrdma: Fix FRWR invalidation error recovery
      xprtrdma: Don't defer MR recovery if ro_map fails
      NFSv4.1: Handle EXCHGID4_FLAG_CONFIRMED_R during NFSv4.1 migration
      NFSv4.1: Use seqid returned by EXCHANGE_ID after state migration
      xprtrdma: Demote "connect" log messages
      xprtrdma: FMR does not need list_del_init()
      xprtrdma: Replace PAGE_MASK with offset_in_page()
      xprtrdma: Fix documenting comments in frwr_ops.c

Dan Carpenter (1):
      NFS: silence a uninitialized variable warning

Jason A. Donenfeld (1):
      sunrpc: use constant time memory comparison for mac

Jeff Layton (1):
      nfs4: add NFSv4 LOOKUPP handlers

NeilBrown (3):
      NFS: only invalidate dentrys that are clearly invalid.
      NFS: guard against confused server in nfs_atomic_open()
      NFS: check for nfs_refresh_inode() errors in nfs_fhget()

Olga Kornievskaia (3):
      PNFS fix EACCESS on commit to DS handling
      PNFS for stateid errors retry against MDS first
      NFSv4.2 fix size storage for nfs42_proc_copy

Peng Tao (3):
      nfs: replace d_add with d_splice_alias in atomic_open
      nfs: add a nfs_ilookup helper
      nfs: add export operations

Trond Myklebust (5):
      SUNRPC: Make slot allocation more reliable
      NFS: Remove unused fields in the page I/O structures
      NFS: Ensure we commit after writeback is complete
      NFS: Fix commit policy for non-blocking calls to nfs_write_inode()
      NFS: Don't run wake_up_bit() when nobody is waiting...

Tuo Chen Peng (1):
      nfs: Fix fscache stat printing in nfs_show_stats()

 fs/lockd/clnt4xdr.c                    |  34 ++-
 fs/lockd/clntxdr.c                     |  58 +++--
 fs/lockd/mon.c                         |  38 +--
 fs/lockd/svc.c                         |  38 +--
 fs/lockd/svc4proc.c                    | 124 ++++++----
 fs/lockd/svcproc.c                     | 124 ++++++----
 fs/lockd/xdr.c                         |  43 ++--
 fs/lockd/xdr4.c                        |  43 ++--
 fs/nfs/Makefile                        |   2 +-
 fs/nfs/callback.c                      |   2 +-
 fs/nfs/callback.h                      |  27 +--
 fs/nfs/callback_proc.c                 |  33 ++-
 fs/nfs/callback_xdr.c                  | 113 +++++----
 fs/nfs/dir.c                           |  42 ++--
 fs/nfs/export.c                        | 177 ++++++++++++++
 fs/nfs/filelayout/filelayout.c         |  31 +--
 fs/nfs/flexfilelayout/flexfilelayout.c |  33 ---
 fs/nfs/inode.c                         |  36 ++-
 fs/nfs/internal.h                      |  18 +-
 fs/nfs/mount_clnt.c                    |  29 ++-
 fs/nfs/nfs2xdr.c                       |  72 ++++--
 fs/nfs/nfs3proc.c                      |   2 +-
 fs/nfs/nfs3xdr.c                       | 153 ++++++++----
 fs/nfs/nfs42proc.c                     |   2 +-
 fs/nfs/nfs42xdr.c                      |  52 +++--
 fs/nfs/nfs4_fs.h                       |   6 +-
 fs/nfs/nfs4client.c                    |   5 +
 fs/nfs/nfs4idmap.c                     |   3 +-
 fs/nfs/nfs4proc.c                      | 109 ++++++---
 fs/nfs/nfs4state.c                     |  16 +-
 fs/nfs/nfs4trace.h                     |  29 +++
 fs/nfs/nfs4xdr.c                       | 408 ++++++++++++++++++++++----------
 fs/nfs/pagelist.c                      |  23 +-
 fs/nfs/proc.c                          |   2 +-
 fs/nfs/super.c                         |   4 +-
 fs/nfs/unlink.c                        |  13 ++
 fs/nfs/write.c                         |  59 ++++-
 fs/nfsd/current_stateid.h              |  36 ++-
 fs/nfsd/nfs2acl.c                      | 116 +++++-----
 fs/nfsd/nfs3acl.c                      |  75 +++---
 fs/nfsd/nfs3proc.c                     | 301 ++++++++++++------------
 fs/nfsd/nfs3xdr.c                      | 164 +++++++------
 fs/nfsd/nfs4callback.c                 |  32 ++-
 fs/nfsd/nfs4proc.c                     | 412 +++++++++++++++++----------------
 fs/nfsd/nfs4state.c                    | 142 +++++++-----
 fs/nfsd/nfs4xdr.c                      |  13 +-
 fs/nfsd/nfsd.h                         |   6 +-
 fs/nfsd/nfsproc.c                      | 206 +++++++++--------
 fs/nfsd/nfssvc.c                       |  24 +-
 fs/nfsd/nfsxdr.c                       |  92 +++++---
 fs/nfsd/xdr.h                          |  50 ++--
 fs/nfsd/xdr3.h                         | 100 +++-----
 fs/nfsd/xdr4.h                         |  78 +++----
 include/linux/lockd/lockd.h            |   4 +-
 include/linux/lockd/xdr.h              |  26 +--
 include/linux/lockd/xdr4.h             |  26 +--
 include/linux/nfs4.h                   |   1 +
 include/linux/nfs_fs.h                 |   1 +
 include/linux/nfs_fs_sb.h              |   2 +
 include/linux/nfs_page.h               |   4 +-
 include/linux/nfs_xdr.h                |  31 ++-
 include/linux/sunrpc/clnt.h            |   6 +-
 include/linux/sunrpc/sched.h           |   2 +-
 include/linux/sunrpc/svc.h             |  21 +-
 include/linux/sunrpc/xdr.h             |  15 +-
 net/sunrpc/auth_gss/gss_krb5_crypto.c  |   3 +-
 net/sunrpc/auth_gss/gss_rpc_upcall.c   |   9 +-
 net/sunrpc/auth_gss/gss_rpc_xdr.c      |  14 +-
 net/sunrpc/auth_gss/gss_rpc_xdr.h      |   4 +-
 net/sunrpc/clnt.c                      |  16 +-
 net/sunrpc/rpcb_clnt.c                 |  82 ++++---
 net/sunrpc/stats.c                     |  16 +-
 net/sunrpc/svc.c                       |  33 +--
 net/sunrpc/xprt.c                      |   8 +-
 net/sunrpc/xprtrdma/fmr_ops.c          |  47 ++--
 net/sunrpc/xprtrdma/frwr_ops.c         |  69 +++---
 net/sunrpc/xprtrdma/rpc_rdma.c         | 125 ++++++----
 net/sunrpc/xprtrdma/transport.c        |   3 +-
 net/sunrpc/xprtrdma/verbs.c            |  55 ++---
 net/sunrpc/xprtrdma/xprt_rdma.h        |  40 +++-
 80 files changed, 2733 insertions(+), 1780 deletions(-)
 create mode 100644 fs/nfs/export.c

Re: [GIT PULL] Please pull NFS client changes for Linux 4.13

[Linus Torvalds]

On Thu, Jul 13, 2017 at 2:16 PM, Anna Schumaker
<schumaker.anna@gmail.com> wrote:
>
>   git://git.linux-nfs.org/projects/anna/linux-nfs.git tags/nfs-for-4.13-1

Btw, your key seems to have expired, and doing a refresh on it doesn't fix it.

I'm sure you've refreshed your key, but apparently that refresh hasn't
been percolated to the public keyservers?

                   Linus

Re: [GIT PULL] Please pull NFS client changes for Linux 4.13

[Christoph Hellwig]

On Thu, Jul 13, 2017 at 02:43:14PM -0700, Linus Torvalds wrote:
> On Thu, Jul 13, 2017 at 2:16 PM, Anna Schumaker
> <schumaker.anna@gmail.com> wrote:
> >
> >   git://git.linux-nfs.org/projects/anna/linux-nfs.git tags/nfs-for-4.13-1
> 
> Btw, your key seems to have expired, and doing a refresh on it doesn't fix it.
> 
> I'm sure you've refreshed your key, but apparently that refresh hasn't
> been percolated to the public keyservers?

As someone who has run into an issue in that area recently:  I manually
had to refresh and re-upload my signing subkey and not just the primary
key, which wa rather confusing and took a long time to sort out.

Re: [GIT PULL] Please pull NFS client changes for Linux 4.13

[Anna Schumaker]

On 07/14/2017 03:09 AM, Christoph Hellwig wrote:
> On Thu, Jul 13, 2017 at 02:43:14PM -0700, Linus Torvalds wrote:
>> On Thu, Jul 13, 2017 at 2:16 PM, Anna Schumaker
>> <schumaker.anna@gmail.com> wrote:
>>>
>>>   git://git.linux-nfs.org/projects/anna/linux-nfs.git tags/nfs-for-4.13-1
>>
>> Btw, your key seems to have expired, and doing a refresh on it doesn't fix it.
>>
>> I'm sure you've refreshed your key, but apparently that refresh hasn't
>> been percolated to the public keyservers?

I assumed I had refreshed it once git let me sign things again, but maybe I missed a step.

> 
> As someone who has run into an issue in that area recently:  I manually
> had to refresh and re-upload my signing subkey and not just the primary
> key, which wa rather confusing and took a long time to sort out.
> 

I'll start here.  Thanks for the tip!

Anna

Re: [GIT PULL] Please pull NFS client changes for Linux 4.13

[Dave Jones]

On Thu, Jul 13, 2017 at 05:16:24PM -0400, Anna Schumaker wrote:
 > Hi Linus,
 > 
 > The following changes since commit 32c1431eea4881a6b17bd7c639315010aeefa452:
 > 
 >   Linux 4.12-rc5 (2017-06-11 16:48:20 -0700)
 > 
 > are available in the git repository at:
 > 
 >   git://git.linux-nfs.org/projects/anna/linux-nfs.git tags/nfs-for-4.13-1
 > 
 > for you to fetch changes up to b4f937cffa66b3d56eb8f586e620d0b223a281a3:
 > 
 >   NFS: Don't run wake_up_bit() when nobody is waiting... (2017-07-13 16:57:18 -0400)

Since this landed, I'm seeing this during boot..

 ==================================================================
 BUG: KASAN: global-out-of-bounds in strscpy+0x4a/0x230
 Read of size 8 at addr ffffffffb4eeaf20 by task nfsd/688
 
 CPU: 0 PID: 688 Comm: nfsd Not tainted 4.12.0-firewall+ #14 
 Call Trace:
  dump_stack+0x68/0x94
  print_address_description+0x2c/0x270
  ? strscpy+0x4a/0x230
  kasan_report+0x239/0x350
  __asan_load8+0x55/0x90
  strscpy+0x4a/0x230
  __ip_map_lookup+0x85/0x150
  ? ip_map_init+0x50/0x50
  ? lock_acquire+0x270/0x270
  svcauth_unix_set_client+0x9f3/0xdc0
  ? svcauth_unix_set_client+0x5/0xdc0
  ? unix_gid_parse+0x340/0x340
  ? kasan_kmalloc+0xbb/0xf0
  ? groups_alloc+0x29/0x80
  ? __kmalloc+0x13b/0x360
  ? groups_alloc+0x29/0x80
  ? groups_alloc+0x48/0x80
  ? svcauth_unix_accept+0x3a5/0x3c0
  svc_set_client+0x50/0x60
  svc_process+0x901/0x10b0
  ? svc_register+0x430/0x430
  ? __might_sleep+0x78/0xf0
  ? preempt_count_sub+0xaf/0x120
  ? __validate_process_creds+0x9e/0x160
  nfsd+0x250/0x380
  ? nfsd+0x5/0x380
  kthread+0x1ab/0x200
  ? nfsd_destroy+0x1f0/0x1f0
  ? __kthread_create_on_node+0x340/0x340
  ret_from_fork+0x27/0x40
 
 The buggy address belongs to the variable:
  str__nfsd__trace_system_name+0x3a0/0x3e0
 
 Memory state around the buggy address:
  ffffffffb4eeae00: 00 00 00 01 fa fa fa fa 00 00 00 00 00 04 fa fa
  ffffffffb4eeae80: fa fa fa fa 04 fa fa fa fa fa fa fa 04 fa fa fa
 >ffffffffb4eeaf00: fa fa fa fa 05 fa fa fa fa fa fa fa 00 00 00 00
                                ^   
  ffffffffb4eeaf80: 00 fa fa fa fa fa fa fa 00 00 05 fa fa fa fa fa
  ffffffffb4eeb000: 00 03 fa fa fa fa fa fa 00 07 fa fa fa fa fa fa
 ==================================================================

Re: [GIT PULL] Please pull NFS client changes for Linux 4.13

[J. Bruce Fields]

On Fri, Jul 14, 2017 at 10:25:43AM -0400, Dave Jones wrote:
> On Thu, Jul 13, 2017 at 05:16:24PM -0400, Anna Schumaker wrote:
>  > Hi Linus,
>  > 
>  > The following changes since commit 32c1431eea4881a6b17bd7c639315010aeefa452:
>  > 
>  >   Linux 4.12-rc5 (2017-06-11 16:48:20 -0700)
>  > 
>  > are available in the git repository at:
>  > 
>  >   git://git.linux-nfs.org/projects/anna/linux-nfs.git tags/nfs-for-4.13-1
>  > 
>  > for you to fetch changes up to b4f937cffa66b3d56eb8f586e620d0b223a281a3:
>  > 
>  >   NFS: Don't run wake_up_bit() when nobody is waiting... (2017-07-13 16:57:18 -0400)
> 
> Since this landed, I'm seeing this during boot..

__ip_map_lookup does have a strcpy, and it looks like that can be
implemented in terms of strscpy.

Based on that backtrace, it should just be copying from
nfsd_program->pg_class, which is initialized to "nfsd" and never
changed.

I spent a few minutes trying to figure out the tracing macros that
define str__nfsd__trace_system_name+0x3a0/0x3e0 and gave up.

So I have no idea what's going on....

--b.

> 
>  ==================================================================
>  BUG: KASAN: global-out-of-bounds in strscpy+0x4a/0x230
>  Read of size 8 at addr ffffffffb4eeaf20 by task nfsd/688
>  
>  CPU: 0 PID: 688 Comm: nfsd Not tainted 4.12.0-firewall+ #14 
>  Call Trace:
>   dump_stack+0x68/0x94
>   print_address_description+0x2c/0x270
>   ? strscpy+0x4a/0x230
>   kasan_report+0x239/0x350
>   __asan_load8+0x55/0x90
>   strscpy+0x4a/0x230
>   __ip_map_lookup+0x85/0x150
>   ? ip_map_init+0x50/0x50
>   ? lock_acquire+0x270/0x270
>   svcauth_unix_set_client+0x9f3/0xdc0
>   ? svcauth_unix_set_client+0x5/0xdc0
>   ? unix_gid_parse+0x340/0x340
>   ? kasan_kmalloc+0xbb/0xf0
>   ? groups_alloc+0x29/0x80
>   ? __kmalloc+0x13b/0x360
>   ? groups_alloc+0x29/0x80
>   ? groups_alloc+0x48/0x80
>   ? svcauth_unix_accept+0x3a5/0x3c0
>   svc_set_client+0x50/0x60
>   svc_process+0x901/0x10b0
>   ? svc_register+0x430/0x430
>   ? __might_sleep+0x78/0xf0
>   ? preempt_count_sub+0xaf/0x120
>   ? __validate_process_creds+0x9e/0x160
>   nfsd+0x250/0x380
>   ? nfsd+0x5/0x380
>   kthread+0x1ab/0x200
>   ? nfsd_destroy+0x1f0/0x1f0
>   ? __kthread_create_on_node+0x340/0x340
>   ret_from_fork+0x27/0x40
>  
>  The buggy address belongs to the variable:
>   str__nfsd__trace_system_name+0x3a0/0x3e0
>  
>  Memory state around the buggy address:
>   ffffffffb4eeae00: 00 00 00 01 fa fa fa fa 00 00 00 00 00 04 fa fa
>   ffffffffb4eeae80: fa fa fa fa 04 fa fa fa fa fa fa fa 04 fa fa fa
>  >ffffffffb4eeaf00: fa fa fa fa 05 fa fa fa fa fa fa fa 00 00 00 00
>                                 ^   
>   ffffffffb4eeaf80: 00 fa fa fa fa fa fa fa 00 00 05 fa fa fa fa fa
>   ffffffffb4eeb000: 00 03 fa fa fa fa fa fa 00 07 fa fa fa fa fa fa
>  ==================================================================

Re: [GIT PULL] Please pull NFS client changes for Linux 4.13

[Linus Torvalds]

On Fri, Jul 14, 2017 at 7:25 AM, Dave Jones <davej@codemonkey.org.uk> wrote:
> On Thu, Jul 13, 2017 at 05:16:24PM -0400, Anna Schumaker wrote:
>  >
>  >   git://git.linux-nfs.org/projects/anna/linux-nfs.git tags/nfs-for-4.13-1
>
> Since this landed, I'm seeing this during boot..
>
>  ==================================================================
>  BUG: KASAN: global-out-of-bounds in strscpy+0x4a/0x230
>  Read of size 8 at addr ffffffffb4eeaf20 by task nfsd/688

Is KASAN aware that strscpy() does the word-at-a-time optimistic reads
of the sources?

The problem may be that the source is initialized from the global
string "nfsd", and KASAN may be unhappy abotu the fact that we read 8
bytes from a 5-byte string (four plus NUL) as we do the word-at-a-time
strscpy..

That said, we do check the size first (because we also *write* 8 bytes
at a time), so maybe KASAN shouldn't even need to care.

Hmm. it really looks to me like this is actually a compiler bug (I'm
using current gcc in F26, which is gcc-7.1.1 - I'm assuming DaveJ is
the same).

This is the source code in __ip_map_lookup:

        struct ip_map ip;
     .....
        strcpy(ip.m_class, class);

and "m_class" is 8 bytes in size:

    struct ip_map {
    ...
            char                    m_class[8]; /* e.g. "nfsd" */
    ...

yet when I look at the generated code for __ip_map_lookup, I see

        movl    $32, %edx       #,
        movq    %r13, %rsi      # class,
        leaq    48(%rax), %rdi  #, tmp126
        call    strscpy #

what's the bug here? Look at that third argument - %rdx. It is
initialized to 32.

WTF?

The code to turn "strcpy()" into "strscpy()" should pick the *smaller*
of the two object sizes as the size argument. How the hell is that
size argument 32?

Am I missing something? DaveJ, do you see the same?

                       Linus

Re: [GIT PULL] Please pull NFS client changes for Linux 4.13

[Andrey Ryabinin]

On 07/14/2017 10:05 PM, Linus Torvalds wrote:
> On Fri, Jul 14, 2017 at 7:25 AM, Dave Jones <davej@codemonkey.org.uk> wrote:
>> On Thu, Jul 13, 2017 at 05:16:24PM -0400, Anna Schumaker wrote:
>>  >
>>  >   git://git.linux-nfs.org/projects/anna/linux-nfs.git tags/nfs-for-4.13-1
>>
>> Since this landed, I'm seeing this during boot..
>>
>>  ==================================================================
>>  BUG: KASAN: global-out-of-bounds in strscpy+0x4a/0x230
>>  Read of size 8 at addr ffffffffb4eeaf20 by task nfsd/688
> 
> Is KASAN aware that strscpy() does the word-at-a-time optimistic reads
> of the sources?
> 

Nope.

> The problem may be that the source is initialized from the global
> string "nfsd", and KASAN may be unhappy abotu the fact that we read 8
> bytes from a 5-byte string (four plus NUL) as we do the word-at-a-time
> strscpy..
> 

Right.

> That said, we do check the size first (because we also *write* 8 bytes
> at a time), so maybe KASAN shouldn't even need to care.
>

Perhaps we could fallback to unoptimzed copy for KASAN case by setting max = 0
in strscpy().

 
> Hmm. it really looks to me like this is actually a compiler bug (I'm
> using current gcc in F26, which is gcc-7.1.1 - I'm assuming DaveJ is
> the same).
> 
> This is the source code in __ip_map_lookup:
> 
>         struct ip_map ip;
>      .....
>         strcpy(ip.m_class, class);
> 
> and "m_class" is 8 bytes in size:
> 
>     struct ip_map {
>     ...
>             char                    m_class[8]; /* e.g. "nfsd" */
>     ...
> 
> yet when I look at the generated code for __ip_map_lookup, I see
> 
>         movl    $32, %edx       #,
>         movq    %r13, %rsi      # class,
>         leaq    48(%rax), %rdi  #, tmp126
>         call    strscpy #
> 
> what's the bug here? Look at that third argume8nt - %rdx. It is
> initialized to 32.
> 
> WTF?
> 


It's not a compiler bug, it's a bug in our strcpy().
Whoever wrote this strcpy() into strscpy() code apparently didn't read carefully
enough gcc manual about __builtin_object_size().

Summary from https://gcc.gnu.org/onlinedocs/gcc/Object-Size-Checking.html :

	__builtin_object_size(ptr, type) returns a constant number of bytes from 'ptr' to the end of the object 'ptr'
	pointer points to. "type" is an integer constant from 0 to 3. If the least significant bit is clear, objects
	are whole variables, if it is set, a closest surrounding subobject is considered the object a pointer points to.
	The second bit determines if maximum or minimum of remaining bytes is computed. 

We have type = 0 in strcpy(), so the least significant bit is clear. So the 'ptr' is considered as a pointer to the whole
variable i.e. pointer to struct ip_map ip;
And the number of bytes from 'ip.m_class' to the end of the ip object is exactly 32.

I suppose that changing the type to 1 should fix this bug.



> The code to turn "strcpy()" into "strscpy()" should pick the *smaller*
> of the two object sizes as the size argument. How the hell is that
> size argument 32?
> 
> Am I missing something? DaveJ, do you see the same?
> 
>                        Linus
> 

Re: [GIT PULL] Please pull NFS client changes for Linux 4.13

[Linus Torvalds]

On Fri, Jul 14, 2017 at 12:43 PM, Andrey Ryabinin
<aryabinin@virtuozzo.com> wrote:
>
>> yet when I look at the generated code for __ip_map_lookup, I see
>>
>>        movl    $32, %edx       #,
>>        movq    %r13, %rsi      # class,
>>        leaq    48(%rax), %rdi  #, tmp126
>>        call    strscpy #
>>
>> what's the bug here? Look at that third argume8nt - %rdx. It is
>> initialized to 32.
>
> It's not a compiler bug, it's a bug in our strcpy().
> Whoever wrote this strcpy() into strscpy() code apparently didn't read carefully
> enough gcc manual about __builtin_object_size().
>
> Summary from https://gcc.gnu.org/onlinedocs/gcc/Object-Size-Checking.html :
>
>         __builtin_object_size(ptr, type) returns a constant number of bytes from 'ptr' to the end of the object 'ptr'
>         pointer points to. "type" is an integer constant from 0 to 3. If the least significant bit is clear, objects
>         are whole variables, if it is set, a closest surrounding subobject is considered the object a pointer points to.
>         The second bit determines if maximum or minimum of remaining bytes is computed.
>
> We have type = 0 in strcpy(), so the least significant bit is clear. So the 'ptr' is considered as a pointer to the whole
> variable i.e. pointer to struct ip_map ip;
> And the number of bytes from 'ip.m_class' to the end of the ip object is exactly 32.
>
> I suppose that changing the type to 1 should fix this bug.

Oh, that absolutely needs to be done.

Because that "strcpy() -> strscpy()" conversion really depends on that
size being the right size (well, in this case minimal safe size) for
the actual accesses, exactly because "strscpy()" is perfectly willing
to write *past* the end of the destination string within that given
size limit (ie it reads and writes in the same 8-byte chunks).

So if you have a small target string that is contained in a big
object, then the "hardened" strcpy() code can actually end up
overwriting things past the end of the strring, even if the string
itself were to have fit in the buffer.

I note that every single use in string.h is buggy, and it worries me
that __compiletime_object_size() does this too. The only user of that
seems to be check_copy_size(), and now I'm a bit worried what that bug
may have hidden.

I find "hardening" code that adds bugs to be particularly bad and
ugly, the same way that I absolutely *hate* debugging code that turns
out to make debugging impossible (we had that with the "better" stack
tracing code that caused kernel panics to kill the machine entirely
rather than show the backtrace, and I'm still bitter about it a decade
after the fact).

There is something actively *evil* about it. Daniel, Kees, please jump on this.

Andrey, thanks for noticing this thing,

                          Linus

Re: [GIT PULL] Please pull NFS client changes for Linux 4.13

[Andrey Rybainin]

On 07/14/2017 10:58 PM, Linus Torvalds wrote:
> On Fri, Jul 14, 2017 at 12:43 PM, Andrey Ryabinin
> <aryabinin@virtuozzo.com> wrote:
>>
>>> yet when I look at the generated code for __ip_map_lookup, I see
>>>
>>>        movl    $32, %edx       #,
>>>        movq    %r13, %rsi      # class,
>>>        leaq    48(%rax), %rdi  #, tmp126
>>>        call    strscpy #
>>>
>>> what's the bug here? Look at that third argume8nt - %rdx. It is
>>> initialized to 32.
>>
>> It's not a compiler bug, it's a bug in our strcpy().
>> Whoever wrote this strcpy() into strscpy() code apparently didn't read carefully
>> enough gcc manual about __builtin_object_size().
>>
>> Summary from https://gcc.gnu.org/onlinedocs/gcc/Object-Size-Checking.html :
>>
>>         __builtin_object_size(ptr, type) returns a constant number of bytes from 'ptr' to the end of the object 'ptr'
>>         pointer points to. "type" is an integer constant from 0 to 3. If the least significant bit is clear, objects
>>         are whole variables, if it is set, a closest surrounding subobject is considered the object a pointer points to.
>>         The second bit determines if maximum or minimum of remaining bytes is computed.
>>
>> We have type = 0 in strcpy(), so the least significant bit is clear. So the 'ptr' is considered as a pointer to the whole
>> variable i.e. pointer to struct ip_map ip;
>> And the number of bytes from 'ip.m_class' to the end of the ip object is exactly 32.
>>
>> I suppose that changing the type to 1 should fix this bug.
> 
> Oh, that absolutely needs to be done.
> 
> Because that "strcpy() -> strscpy()" conversion really depends on that
> size being the right size (well, in this case minimal safe size) for
> the actual accesses, exactly because "strscpy()" is perfectly willing
> to write *past* the end of the destination string within that given
> size limit (ie it reads and writes in the same 8-byte chunks).
> 
> So if you have a small target string that is contained in a big
> object, then the "hardened" strcpy() code can actually end up
> overwriting things past the end of the strring, even if the string
> itself were to have fit in the buffer.
> 
> I note that every single use in string.h is buggy, and it worries me
> that __compiletime_object_size() does this too. The only user of that
> seems to be check_copy_size(), and now I'm a bit worried what that bug
> may have hidden.
> 
> I find "hardening" code that adds bugs to be particularly bad and
> ugly, the same way that I absolutely *hate* debugging code that turns
> out to make debugging impossible (we had that with the "better" stack
> tracing code that caused kernel panics to kill the machine entirely
> rather than show the backtrace, and I'm still bitter about it a decade
> after the fact).
> 

A have some more news to make you even more "happier" :)
strcpy() choose to copy 32-bytes instead of smaller 5-bytes because it has one more bug :)

GCC couldn't determine size of class (which is 5-byte string):
	strcpy(ip.m_class, class);

So, p_size = 32 and q_size  = -1, this "if (p_size == (size_t)-1 && q_size == (size_t)-1)" is false
(because of bogus '&&', obviously we should have '||' here)

and since (32 < (size_t)-1) 
	if (strscpy(p, q, p_size < q_size ? p_size : q_size) < 0)

we end up with 32-bytes strscpy().

Enjoy :)


> There is something actively *evil* about it. Daniel, Kees, please jump on this.
> 
> Andrey, thanks for noticing this thing,
> 
>                           Linus
> 

Re: [GIT PULL] Please pull NFS client changes for Linux 4.13

[Daniel Micay]

On Fri, 2017-07-14 at 12:58 -0700, Linus Torvalds wrote:
> On Fri, Jul 14, 2017 at 12:43 PM, Andrey Ryabinin
> <aryabinin@virtuozzo.com> wrote:
> > 
> > > yet when I look at the generated code for __ip_map_lookup, I see
> > > 
> > >        movl    $32, %edx       #,
> > >        movq    %r13, %rsi      # class,
> > >        leaq    48(%rax), %rdi  #, tmp126
> > >        call    strscpy #
> > > 
> > > what's the bug here? Look at that third argume8nt - %rdx. It is
> > > initialized to 32.
> > 
> > It's not a compiler bug, it's a bug in our strcpy().
> > Whoever wrote this strcpy() into strscpy() code apparently didn't
> > read carefully
> > enough gcc manual about __builtin_object_size().
> > 
> > Summary from https://gcc.gnu.org/onlinedocs/gcc/Object-Size-Checking
> > .html :
> > 
> >         __builtin_object_size(ptr, type) returns a constant number
> > of bytes from 'ptr' to the end of the object 'ptr'
> >         pointer points to. "type" is an integer constant from 0 to
> > 3. If the least significant bit is clear, objects
> >         are whole variables, if it is set, a closest surrounding
> > subobject is considered the object a pointer points to.
> >         The second bit determines if maximum or minimum of remaining
> > bytes is computed.
> > 
> > We have type = 0 in strcpy(), so the least significant bit is clear.
> > So the 'ptr' is considered as a pointer to the whole
> > variable i.e. pointer to struct ip_map ip;
> > And the number of bytes from 'ip.m_class' to the end of the ip
> > object is exactly 32.
> > 
> > I suppose that changing the type to 1 should fix this bug.
> 
> Oh, that absolutely needs to be done.
> 
> Because that "strcpy() -> strscpy()" conversion really depends on that
> size being the right size (well, in this case minimal safe size) for
> the actual accesses, exactly because "strscpy()" is perfectly willing
> to write *past* the end of the destination string within that given
> size limit (ie it reads and writes in the same 8-byte chunks).
> 
> So if you have a small target string that is contained in a big
> object, then the "hardened" strcpy() code can actually end up
> overwriting things past the end of the strring, even if the string
> itself were to have fit in the buffer.
> 
> I note that every single use in string.h is buggy, and it worries me
> that __compiletime_object_size() does this too. The only user of that
> seems to be check_copy_size(), and now I'm a bit worried what that bug
> may have hidden.
> 
> I find "hardening" code that adds bugs to be particularly bad and
> ugly, the same way that I absolutely *hate* debugging code that turns
> out to make debugging impossible (we had that with the "better" stack
> tracing code that caused kernel panics to kill the machine entirely
> rather than show the backtrace, and I'm still bitter about it a decade
> after the fact).
> 
> There is something actively *evil* about it. Daniel, Kees, please jump
> on this.
> 
> Andrey, thanks for noticing this thing,
> 
>                           Linus

The issue is the usage of strscpy then, not the __builtin_object_size
type parameter. The type is set 0 rather than 1 to be more lenient by
not detecting intra-object overflow, which is going to come later.

If strscpy treats the count parameter as a *guarantee* of the dest size
rather than a limit, it's wrong to use it there, whether or not the type
parameter for __builtin_object_size is 0 or 1 since it can still return
a larger size. It's a limit with no guaranteed minimum.

My initial patch used strlcpy there, because I wasn't aware of strscpy
before it was suggested:

http://www.openwall.com/lists/kernel-hardening/2017/05/04/11

I was wrong to move it to strscpy. It could be switched back to strlcpy
again unless the kernel considers the count parameter to be a guarantee
that could be leveraged in the future. Using the fortified strlen +
memcpy would provide the improvement that strscpy was meant to provide
there over strlcpy.

Re: [GIT PULL] Please pull NFS client changes for Linux 4.13

[Linus Torvalds]

On Fri, Jul 14, 2017 at 1:38 PM, Daniel Micay <danielmicay@gmail.com> wrote:
>
> If strscpy treats the count parameter as a *guarantee* of the dest size
> rather than a limit,

No, it's a *limit*.

And by a *limit*, I mean that we know that we can access both source
and destination within that limit.

> My initial patch used strlcpy there, because I wasn't aware of strscpy
> before it was suggested:

Since I'm looking at this, I note that the "strlcpy()" code is
complete garbage too, and has that same

     p_size == (size_t)-1 && q_size == (size_t)-1

check which is wrong.  Of course, in strlcpy, q_size is never actually
*used*, so the whole check seems bogus.

But no, strlcpy() is complete garbage, and should never be used. It is
truly a shit interface, and anybody who uses it is by definition
buggy.

Why? Because the return value of "strlcpy()" is defined to be ignoring
the limit, so you FUNDAMENTALLY must not use that thing on untrusted
source strings.

But since the whole *point* of people using it is for untrusted
sources, it by definition is garbage.

Ergo: don't use strlcpy(). It's unbelievable crap. It's wrong. There's
a reason we defined "strscpy()" as the way to do safe copies
(strncpy(), of course, is broken for both lack of NUL termination
_and_ for excessive NUL termination when a NUL did exist).

So quite frankly, this hardening code needs to be looked at again. And
no, if it uses "strlcpy()", then it's not hardering, it's just a pile
of crap.

Yes, I'm annoyed. I really get very very annoyed by "hardening" code
that does nothing of the kind.

                   Linus

Re: [GIT PULL] Please pull NFS client changes for Linux 4.13

[Daniel Micay]

On Fri, 2017-07-14 at 13:50 -0700, Linus Torvalds wrote:
> On Fri, Jul 14, 2017 at 1:38 PM, Daniel Micay <danielmicay@gmail.com>
> wrote:
> > 
> > If strscpy treats the count parameter as a *guarantee* of the dest
> > size
> > rather than a limit,
> 
> No, it's a *limit*.
> 
> And by a *limit*, I mean that we know that we can access both source
> and destination within that limit.

FORTIFY_SOURCE needs to be able to pass a limit without implying that
there's a minimum. That's the distinction I was trying to make. It's
wrong to use anything where it's interpreted as a minimum here. Using
__builtin_object_size(ptr, 0) vs. __builtin_object_size(ptr, 1) doesn't
avoid the problem. __builtin_object_size(ptr, 1) returns a maximum among
the possible buffer sizes just like 0. It's just stricter, i.e. catches
intra-object overflow, which isn't desirable for the first take since it
will cause compatibility issues. There's code using memcpy,
copy_to_user, etc. to read / write multiple fields with a pointer to the
first one passed as the source / destination.

> > My initial patch used strlcpy there, because I wasn't aware of
> > strscpy
> > before it was suggested:
> 
> Since I'm looking at this, I note that the "strlcpy()" code is
> complete garbage too, and has that same
> 
>      p_size == (size_t)-1 && q_size == (size_t)-1
> 
> check which is wrong.  Of course, in strlcpy, q_size is never actually
> *used*, so the whole check seems bogus.

That check is only an optimization. __builtin_object_size always returns
a constant, and it's (size_t)-1 when no limit could be found.

The reason q_size isn't used is because it doesn't yet prevent read
overflow. The commit message mentions that among the current limitations
along with __builtin_object_size(ptr, 1).

> But no, strlcpy() is complete garbage, and should never be used. It is
> truly a shit interface, and anybody who uses it is by definition
> buggy.
> 
> Why? Because the return value of "strlcpy()" is defined to be ignoring
> the limit, so you FUNDAMENTALLY must not use that thing on untrusted
> source strings.
> 
> But since the whole *point* of people using it is for untrusted
> sources, it by definition is garbage.
> 
> Ergo: don't use strlcpy(). It's unbelievable crap. It's wrong. There's
> a reason we defined "strscpy()" as the way to do safe copies
> (strncpy(), of course, is broken for both lack of NUL termination
> _and_ for excessive NUL termination when a NUL did exist).

Sure, it doesn't prevent read overflow (but it's not worse than strcpy,
which is the purpose) which is why I said this:

"The fortified string functions should place a limit on reads from the
source. For strcat/strcpy, these could just be a variant of strlcat /
strlcpy using the size limit as a bound on both the source and
destination, with the return value only reporting whether truncation
occurred rather than providing the source length. It would be an easier
API for developers to use too and not that it really matters but it
would be more efficient for the case where truncation is intended."

That's why strscpy was suggested and I switched to that + updated the
commit message to only mention strcat, but it's wrong to use it here
because __builtin_object_size(p, 0) / __builtin_object_size(p, 1) are
only a guaranteed maximum length with no minimum guarantee.

Re: [GIT PULL] Please pull NFS client changes for Linux 4.13

[Daniel Micay]

> The reason q_size isn't used is because it doesn't yet prevent read
> overflow. The commit message mentions that among the current
> limitations
> along with __builtin_object_size(ptr, 1).

Er rather, in strlcat, the q_size is unused after the fast path is
because strnlen obtains the constant again itself.

Re: [GIT PULL] Please pull NFS client changes for Linux 4.13

[Daniel Micay]

> My initial patch used strlcpy there, because I wasn't aware of strscpy
> before it was suggested:
> 
> http://www.openwall.com/lists/kernel-hardening/2017/05/04/11
> 
> I was wrong to move it to strscpy. It could be switched back to
> strlcpy
> again unless the kernel considers the count parameter to be a
> guarantee
> that could be leveraged in the future. Using the fortified strlen +
> memcpy would provide the improvement that strscpy was meant to provide
> there over strlcpy.

Similarly, the FORTIFY_SOURCE strcat uses strlcat with the assumption
that the count parameter is a limit, not a guarantee for a optimization.
There's only a C implementation and it currently doesn't, but if it's
meant to be a guarantee then the strcat needs to be changed too.

I'll make a fix moving away both from the existing functions.

Re: [GIT PULL] Please pull NFS client changes for Linux 4.13

[Daniel Micay]

> I find "hardening" code that adds bugs to be particularly bad and
> ugly, the same way that I absolutely *hate* debugging code that turns
> out to make debugging impossible (we had that with the "better" stack
> tracing code that caused kernel panics to kill the machine entirely
> rather than show the backtrace, and I'm still bitter about it a decade
> after the fact).

Agree, it's very important for this code to be correct and the string
functions have some subtleties so it needs scrutiny. I messed up strcpy
between v1 and v2 trying to add a proper read overflow check. My fault
for not looking more closely at strscpy before adopting it based on my
misinterpretation of the API.

This is primarily a bug finding feature right now and it has gotten a
few fixed that actually matter (most were unimportant memcpy read past
end of string constant but not all). I don't think it has another bug
like this strscpy misuse itself, but there will need to be some more
fixes for minor read overflows, etc. elsewhere in the tree before it'll
actually make sense as a hardening feature because it can turn a benign
read overflow into a DoS via BUG(). I think it will be fine for 4.13,
but I definitely wouldn't propose 'default y' for a while, even if there
was no performance cost (and there is).

Fix for this issue is here in case anyone just looks only at this thread
(realized I should have passed send-email a reply id):

http://marc.info/?l=linux-fsdevel&m=150006772418003&w=2

Re: [GIT PULL] Please pull NFS client changes for Linux 4.13

[Dave Jones]

On Fri, Jul 14, 2017 at 12:05:02PM -0700, Linus Torvalds wrote:
 > On Fri, Jul 14, 2017 at 7:25 AM, Dave Jones <davej@codemonkey.org.uk> wrote:
 > > On Thu, Jul 13, 2017 at 05:16:24PM -0400, Anna Schumaker wrote:
 > >  >
 > >  >   git://git.linux-nfs.org/projects/anna/linux-nfs.git tags/nfs-for-4.13-1
 > >
 > > Since this landed, I'm seeing this during boot..
 > >
 > >  ==================================================================
 > >  BUG: KASAN: global-out-of-bounds in strscpy+0x4a/0x230
 > >  Read of size 8 at addr ffffffffb4eeaf20 by task nfsd/688
 > 
 > Is KASAN aware that strscpy() does the word-at-a-time optimistic reads
 > of the sources?
 > 
 > The problem may be that the source is initialized from the global
 > string "nfsd", and KASAN may be unhappy abotu the fact that we read 8
 > bytes from a 5-byte string (four plus NUL) as we do the word-at-a-time
 > strscpy..
 > 
 > That said, we do check the size first (because we also *write* 8 bytes
 > at a time), so maybe KASAN shouldn't even need to care.
 > 
 > Hmm. it really looks to me like this is actually a compiler bug (I'm
 > using current gcc in F26, which is gcc-7.1.1 - I'm assuming DaveJ is
 > the same).

Debian's 6.4.0

 > This is the source code in __ip_map_lookup:
 > 
 >         struct ip_map ip;
 >      .....
 >         strcpy(ip.m_class, class);
 > 
 > and "m_class" is 8 bytes in size:
 > 
 >     struct ip_map {
 >     ...
 >             char                    m_class[8]; /* e.g. "nfsd" */
 >     ...
 > 
 > yet when I look at the generated code for __ip_map_lookup, I see
 > 
 >         movl    $32, %edx       #,
 >         movq    %r13, %rsi      # class,
 >         leaq    48(%rax), %rdi  #, tmp126
 >         call    strscpy #
 > 
 > what's the bug here? Look at that third argument - %rdx. It is
 > initialized to 32.
 > 
 > WTF?
 > 
 > The code to turn "strcpy()" into "strscpy()" should pick the *smaller*
 > of the two object sizes as the size argument. How the hell is that
 > size argument 32?
 > 
 > Am I missing something? DaveJ, do you see the same?

My compiler seems to have replaced the call with an inlined copy afaics.

0000000000000be0 <__ip_map_lookup>:
{
     be0:       e8 00 00 00 00          callq  be5 <__ip_map_lookup+0x5>
     be5:       55                      push   %rbp
     be6:       48 b8 00 00 00 00 00    movabs $0xdffffc0000000000,%rax
     bed:       fc ff df 
     bf0:       48 89 e5                mov    %rsp,%rbp
     bf3:       41 57                   push   %r15
     bf5:       41 56                   push   %r14
     bf7:       4c 8d 32                lea    (%rdx),%r14
        if (strscpy(p, q, p_size < q_size ? p_size : q_size) < 0)
     bfa:       ba 20 00 00 00          mov    $0x20,%edx
     bff:       41 55                   push   %r13
     c01:       4c 8d 2e                lea    (%rsi),%r13
     c04:       41 54                   push   %r12
     c06:       53                      push   %rbx
     c07:       48 8d 1f                lea    (%rdi),%rbx
     c0a:       48 8d a4 24 60 ff ff    lea    -0xa0(%rsp),%rsp
     c11:       ff 
     c12:       49 89 e4                mov    %rsp,%r12
     c15:       49 c1 ec 03             shr    $0x3,%r12
     c19:       48 c7 04 24 b3 8a b5    movq   $0x41b58ab3,(%rsp)
     c20:       41 
     c21:       48 c7 44 24 08 00 00    movq   $0x0,0x8(%rsp)
     c28:       00 00 
     c2a:       48 c7 44 24 10 00 00    movq   $0x0,0x10(%rsp)
     c31:       00 00 
     c33:       48 8d 7c 24 50          lea    0x50(%rsp),%rdi
     c38:       4d 8d 24 04             lea    (%r12,%rax,1),%r12
     c3c:       41 c7 04 24 f1 f1 f1    movl   $0xf1f1f1f1,(%r12)
     c43:       f1 
     c44:       41 c7 44 24 0c 00 00    movl   $0xf4f40000,0xc(%r12)
     c4b:       f4 f4 
     c4d:       65 48 8b 04 25 28 00    mov    %gs:0x28,%rax
     c54:       00 00 
     c56:       48 89 84 24 98 00 00    mov    %rax,0x98(%rsp)
     c5d:       00 
     c5e:       31 c0                   xor    %eax,%eax
     c60:       e8 00 00 00 00          callq  c65 <__ip_map_lookup+0x85>
     c65:       48 85 c0                test   %rax,%rax
     c68:       0f 88 a0 00 00 00       js     d0e <__ip_map_lookup+0x12e>
        ip.m_addr = *addr;
     c6e:       be 10 00 00 00          mov    $0x10,%esi
     c73:       49 8d 3e                lea    (%r14),%rdi
     c76:       e8 00 00 00 00          callq  c7b <__ip_map_lookup+0x9b>
     c7b:       49 8b 56 08             mov    0x8(%r14),%rdx


But that mov $0x20,%edx looks like it might be the same value we're talking about.

	Dave

Re: [GIT PULL] Please pull NFS client changes for Linux 4.13

[Dave Jones]

On Fri, Jul 14, 2017 at 10:25:43AM -0400, Dave Jones wrote:
 > On Thu, Jul 13, 2017 at 05:16:24PM -0400, Anna Schumaker wrote:
 >  > Hi Linus,
 >  > 
 >  > The following changes since commit 32c1431eea4881a6b17bd7c639315010aeefa452:
 >  > 
 >  >   Linux 4.12-rc5 (2017-06-11 16:48:20 -0700)
 >  > 
 >  > are available in the git repository at:
 >  > 
 >  >   git://git.linux-nfs.org/projects/anna/linux-nfs.git tags/nfs-for-4.13-1
 >  > 
 >  > for you to fetch changes up to b4f937cffa66b3d56eb8f586e620d0b223a281a3:
 >  > 
 >  >   NFS: Don't run wake_up_bit() when nobody is waiting... (2017-07-13 16:57:18 -0400)
 > 
 > Since this landed, I'm seeing this during boot..
 > 
 >  ==================================================================
 >  BUG: KASAN: global-out-of-bounds in strscpy+0x4a/0x230
 >  Read of size 8 at addr ffffffffb4eeaf20 by task nfsd/688

Now that this one got fixed, this one fell out instead..
Will dig deeper tomorrow.

==================================================================
BUG: KASAN: global-out-of-bounds in call_start+0x93/0x100
Read of size 8 at addr ffffffff8d582588 by task kworker/0:1/22

CPU: 0 PID: 22 Comm: kworker/0:1 Not tainted 4.13.0-rc1-firewall+ #1 
Workqueue: rpciod rpc_async_schedule
Call Trace:
 dump_stack+0x68/0x94
 print_address_description+0x2c/0x270
 ? call_start+0x93/0x100
 kasan_report+0x239/0x350
 __asan_load8+0x55/0x90
 call_start+0x93/0x100
 ? rpc_default_callback+0x10/0x10
 ? rpc_default_callback+0x10/0x10
 __rpc_execute+0x170/0x740
 ? rpc_wake_up_queued_task+0x50/0x50
 ? __lock_is_held+0x9f/0x110
 rpc_async_schedule+0x12/0x20
 process_one_work+0x4ba/0xb10
 ? process_one_work+0x401/0xb10
 ? pwq_dec_nr_in_flight+0x120/0x120
 worker_thread+0x91/0x670
 ? __sched_text_start+0x8/0x8
 kthread+0x1ab/0x200
 ? process_one_work+0xb10/0xb10
 ? __kthread_create_on_node+0x340/0x340
 ret_from_fork+0x27/0x40

The buggy address belongs to the variable:
 nfs_cb_version+0x8/0x740

Memory state around the buggy address:
 ffffffff8d582480: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffffff8d582500: 00 00 00 00 00 00 00 00 00 00 fa fa fa fa fa fa
>ffffffff8d582580: 00 fa fa fa fa fa fa fa 00 00 00 00 00 00 00 00
                      ^
 ffffffff8d582600: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffffff8d582680: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================

Re: [GIT PULL] Please pull NFS client changes for Linux 4.13

[Trond Myklebust]

Hi Dave,

On Sun, 2017-07-16 at 17:15 -0400, Dave Jones wrote:
> On Fri, Jul 14, 2017 at 10:25:43AM -0400, Dave Jones wrote:
>  > On Thu, Jul 13, 2017 at 05:16:24PM -0400, Anna Schumaker wrote:
>  >  > Hi Linus,
>  >  > 
>  >  > The following changes since commit
> 32c1431eea4881a6b17bd7c639315010aeefa452:
>  >  > 
>  >  >   Linux 4.12-rc5 (2017-06-11 16:48:20 -0700)
>  >  > 
>  >  > are available in the git repository at:
>  >  > 
>  >  >   git://git.linux-nfs.org/projects/anna/linux-nfs.git tags/nfs-
> for-4.13-1
>  >  > 
>  >  > for you to fetch changes up to
> b4f937cffa66b3d56eb8f586e620d0b223a281a3:
>  >  > 
>  >  >   NFS: Don't run wake_up_bit() when nobody is waiting... (2017-
> 07-13 16:57:18 -0400)
>  > 
>  > Since this landed, I'm seeing this during boot..
>  > 
>  >  =================================================================
> =
>  >  BUG: KASAN: global-out-of-bounds in strscpy+0x4a/0x230
>  >  Read of size 8 at addr ffffffffb4eeaf20 by task nfsd/688
> 
> Now that this one got fixed, this one fell out instead..
> Will dig deeper tomorrow.
> 
> ==================================================================
> BUG: KASAN: global-out-of-bounds in call_start+0x93/0x100
> Read of size 8 at addr ffffffff8d582588 by task kworker/0:1/22
> 
> CPU: 0 PID: 22 Comm: kworker/0:1 Not tainted 4.13.0-rc1-firewall+ #1 
> Workqueue: rpciod rpc_async_schedule
> Call Trace:
>  dump_stack+0x68/0x94
>  print_address_description+0x2c/0x270
>  ? call_start+0x93/0x100
>  kasan_report+0x239/0x350
>  __asan_load8+0x55/0x90
>  call_start+0x93/0x100
>  ? rpc_default_callback+0x10/0x10
>  ? rpc_default_callback+0x10/0x10
>  __rpc_execute+0x170/0x740
>  ? rpc_wake_up_queued_task+0x50/0x50
>  ? __lock_is_held+0x9f/0x110
>  rpc_async_schedule+0x12/0x20
>  process_one_work+0x4ba/0xb10
>  ? process_one_work+0x401/0xb10
>  ? pwq_dec_nr_in_flight+0x120/0x120
>  worker_thread+0x91/0x670
>  ? __sched_text_start+0x8/0x8
>  kthread+0x1ab/0x200
>  ? process_one_work+0xb10/0xb10
>  ? __kthread_create_on_node+0x340/0x340
>  ret_from_fork+0x27/0x40
> 
> The buggy address belongs to the variable:
>  nfs_cb_version+0x8/0x740

Does the following patch fix it?

Cheers
  Trond

8<--------------------------------------
>From b9230cdfbbee90178a1318d20cd3373ffb758788 Mon Sep 17 00:00:00 2001
From: Trond Myklebust <trond.myklebust@primarydata.com>
Date: Sun, 16 Jul 2017 18:52:18 -0400
Subject: [PATCH] nfsd: Fix a memory scribble in the callback channel

The offset of the entry in struct rpc_version has to match the version
number.

Reported-by: Dave Jones <davej@codemonkey.org.uk>
Fixes: 1c5876ddbdb4 ("sunrpc: move p_count out of struct rpc_procinfo")
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
---
 fs/nfsd/nfs4callback.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
index b45083c0f9ae..49b0a9e7ff18 100644
--- a/fs/nfsd/nfs4callback.c
+++ b/fs/nfsd/nfs4callback.c
@@ -720,8 +720,8 @@ static const struct rpc_version nfs_cb_version4 = {
 	.counts			= nfs4_cb_counts,
 };
 
-static const struct rpc_version *nfs_cb_version[] = {
-	&nfs_cb_version4,
+static const struct rpc_version *nfs_cb_version[2] = {
+	[1] = &nfs_cb_version4,
 };
 
 static const struct rpc_program cb_program;
@@ -795,7 +795,7 @@ static int setup_callback_client(struct nfs4_client *clp, struct nfs4_cb_conn *c
 		.saddress	= (struct sockaddr *) &conn->cb_saddr,
 		.timeout	= &timeparms,
 		.program	= &cb_program,
-		.version	= 0,
+		.version	= 1,
 		.flags		= (RPC_CLNT_CREATE_NOPING | RPC_CLNT_CREATE_QUIET),
 	};
 	struct rpc_clnt *client;
-- 
2.13.3

-- 
Trond Myklebust
Linux NFS client maintainer, PrimaryData
trond.myklebust@primarydata.com

Re: [GIT PULL] Please pull NFS client changes for Linux 4.13

[davej]

On Sun, Jul 16, 2017 at 10:57:27PM +0000, Trond Myklebust wrote:
 
 > > BUG: KASAN: global-out-of-bounds in call_start+0x93/0x100
 > > Read of size 8 at addr ffffffff8d582588 by task kworker/0:1/22
 > 
 > Does the following patch fix it?

Yep, seems to do the trick!

	Dave

Re: [GIT PULL] Please pull NFS client changes for Linux 4.13

[Linus Torvalds]

On Sun, Jul 16, 2017 at 8:05 PM, davej@codemonkey.org.uk
<davej@codemonkey.org.uk> wrote:
> On Sun, Jul 16, 2017 at 10:57:27PM +0000, Trond Myklebust wrote:
>
>  > > BUG: KASAN: global-out-of-bounds in call_start+0x93/0x100
>  > > Read of size 8 at addr ffffffff8d582588 by task kworker/0:1/22
>  >
>  > Does the following patch fix it?
>
> Yep, seems to do the trick!

I'm assuming I'll get this fix through a future pull request, and am
not applying the patch as-is. Just FYI.

                     Linus

[GIT PULL] Please pull an nfsd bugfix for 4.13

[bfields]

Please pull:

  git://linux-nfs.org/~bfields/linux.git tags/nfsd-4.13-1

One fix for a problem introduced in the most recent merge window and
found by Dave Jones and KASAN.

--b.

Trond Myklebust (1):
      nfsd: Fix a memory scribble in the callback channel

 fs/nfsd/nfs4callback.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

Re: [GIT PULL] Please pull NFS client changes for Linux 4.13

[davej]

Another NFSv4 KASAN splat, this time from rc3.


==================================================================
BUG: KASAN: use-after-free in nfs4_exchange_id_done+0x3d7/0x8e0 [nfsv4]
Read of size 8 at addr ffff8804508af528 by task kworker/2:1/34

CPU: 2 PID: 34 Comm: kworker/2:1 Not tainted 4.13.0-rc3-think+ #1 
Workqueue: rpciod rpc_async_schedule [sunrpc]
Call Trace:
 dump_stack+0x68/0xa1
 print_address_description+0xd9/0x270
 kasan_report+0x257/0x370
 ? nfs4_exchange_id_done+0x3d7/0x8e0 [nfsv4]
 check_memory_region+0x13a/0x1a0
 __asan_loadN+0xf/0x20
 nfs4_exchange_id_done+0x3d7/0x8e0 [nfsv4]
 ? nfs4_exchange_id_release+0xb0/0xb0 [nfsv4]
 rpc_exit_task+0x69/0x110 [sunrpc]
 ? rpc_destroy_wait_queue+0x20/0x20 [sunrpc]
 ? rpc_destroy_wait_queue+0x20/0x20 [sunrpc]
 __rpc_execute+0x1a0/0x840 [sunrpc]
 ? rpc_wake_up_queued_task+0x50/0x50 [sunrpc]
 ? __lock_is_held+0x9a/0x100
 ? debug_lockdep_rcu_enabled.part.16+0x1a/0x30
 rpc_async_schedule+0x12/0x20 [sunrpc]
 process_one_work+0x4d5/0xa70
 ? flush_delayed_work+0x70/0x70
 ? lock_acquire+0xfc/0x220
 worker_thread+0x88/0x630
 ? pci_mmcfg_check_reserved+0xc0/0xc0
 kthread+0x1a6/0x1f0
 ? process_one_work+0xa70/0xa70
 ? kthread_create_on_node+0xc0/0xc0
 ret_from_fork+0x27/0x40

Allocated by task 1:
 save_stack_trace+0x1b/0x20
 save_stack+0x46/0xd0
 kasan_kmalloc+0xad/0xe0
 kasan_slab_alloc+0x12/0x20
 kmem_cache_alloc+0xe0/0x2f0
 getname_flags+0x43/0x220
 getname+0x12/0x20
 do_sys_open+0x14c/0x2b0
 SyS_open+0x1e/0x20
 do_syscall_64+0xea/0x260
 return_from_SYSCALL_64+0x0/0x7a

Freed by task 1:
 save_stack_trace+0x1b/0x20
 save_stack+0x46/0xd0
 kasan_slab_free+0x72/0xc0
 kmem_cache_free+0xa8/0x300
 putname+0x80/0x90
 do_sys_open+0x22f/0x2b0
 SyS_open+0x1e/0x20
 do_syscall_64+0xea/0x260
 return_from_SYSCALL_64+0x0/0x7a

The buggy address belongs to the object at ffff8804508aeac0\x0a which belongs to the cache names_cache of size 4096
The buggy address is located 2664 bytes inside of\x0a 4096-byte region [ffff8804508aeac0, ffff8804508afac0)
The buggy address belongs to the page:
page:ffffea0011422a00 count:1 mapcount:0 mapping:          (null) index:0x0
[CONT START]  compound_mapcount: 0
flags: 0x8000000000008100(slab|head)
raw: 8000000000008100 0000000000000000 0000000000000000 0000000100070007
raw: ffffea00113d6020 ffffea001136e220 ffff8804664f8040 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8804508af400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8804508af480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8804508af500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                  ^
 ffff8804508af580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8804508af600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Re: [GIT PULL] Please pull NFS client changes for Linux 4.13

[Linus Torvalds]

On Mon, Jul 31, 2017 at 8:43 AM, davej@codemonkey.org.uk
<davej@codemonkey.org.uk> wrote:
> Another NFSv4 KASAN splat, this time from rc3.
>
> BUG: KASAN: use-after-free in nfs4_exchange_id_done+0x3d7/0x8e0 [nfsv4]

Ugh. It's really hard to tell what access that it - KASAN doesn't
actually give enough information. There's lots of 8-byte accesses
there in that function.

Any chance of getting the output from

   ./scripts/faddr2line vmlinux nfs4_exchange_id_done+0x3d7/0x8e0

or something? That would be extremely useful in general for
stacktraces, but it's doubly useful for KASAN because most *other*
stacktraces tend to have a very limited number of things that can warn
(ie there's one or two WARN_ON() calls in a function), but KASAN can
have tens or hundreds..

                       Linus


> Read of size 8 at addr ffff8804508af528 by task kworker/2:1/34
>
> CPU: 2 PID: 34 Comm: kworker/2:1 Not tainted 4.13.0-rc3-think+ #1
> Workqueue: rpciod rpc_async_schedule [sunrpc]
> Call Trace:
>  dump_stack+0x68/0xa1
>  print_address_description+0xd9/0x270
>  kasan_report+0x257/0x370
>  ? nfs4_exchange_id_done+0x3d7/0x8e0 [nfsv4]
>  check_memory_region+0x13a/0x1a0
>  __asan_loadN+0xf/0x20
>  nfs4_exchange_id_done+0x3d7/0x8e0 [nfsv4]
>  ? nfs4_exchange_id_release+0xb0/0xb0 [nfsv4]
>  rpc_exit_task+0x69/0x110 [sunrpc]
>  ? rpc_destroy_wait_queue+0x20/0x20 [sunrpc]
>  ? rpc_destroy_wait_queue+0x20/0x20 [sunrpc]
>  __rpc_execute+0x1a0/0x840 [sunrpc]
>  ? rpc_wake_up_queued_task+0x50/0x50 [sunrpc]
>  ? __lock_is_held+0x9a/0x100
>  ? debug_lockdep_rcu_enabled.part.16+0x1a/0x30
>  rpc_async_schedule+0x12/0x20 [sunrpc]
>  process_one_work+0x4d5/0xa70
>  ? flush_delayed_work+0x70/0x70
>  ? lock_acquire+0xfc/0x220
>  worker_thread+0x88/0x630
>  ? pci_mmcfg_check_reserved+0xc0/0xc0
>  kthread+0x1a6/0x1f0
>  ? process_one_work+0xa70/0xa70
>  ? kthread_create_on_node+0xc0/0xc0
>  ret_from_fork+0x27/0x40
>
> Allocated by task 1:
>  save_stack_trace+0x1b/0x20
>  save_stack+0x46/0xd0
>  kasan_kmalloc+0xad/0xe0
>  kasan_slab_alloc+0x12/0x20
>  kmem_cache_alloc+0xe0/0x2f0
>  getname_flags+0x43/0x220
>  getname+0x12/0x20
>  do_sys_open+0x14c/0x2b0
>  SyS_open+0x1e/0x20
>  do_syscall_64+0xea/0x260
>  return_from_SYSCALL_64+0x0/0x7a
>
> Freed by task 1:
>  save_stack_trace+0x1b/0x20
>  save_stack+0x46/0xd0
>  kasan_slab_free+0x72/0xc0
>  kmem_cache_free+0xa8/0x300
>  putname+0x80/0x90
>  do_sys_open+0x22f/0x2b0
>  SyS_open+0x1e/0x20
>  do_syscall_64+0xea/0x260
>  return_from_SYSCALL_64+0x0/0x7a
>
> The buggy address belongs to the object at ffff8804508aeac0\x0a which belongs to the cache names_cache of size 4096
> The buggy address is located 2664 bytes inside of\x0a 4096-byte region [ffff8804508aeac0, ffff8804508afac0)
> The buggy address belongs to the page:
> page:ffffea0011422a00 count:1 mapcount:0 mapping:          (null) index:0x0
> [CONT START]  compound_mapcount: 0
> flags: 0x8000000000008100(slab|head)
> raw: 8000000000008100 0000000000000000 0000000000000000 0000000100070007
> raw: ffffea00113d6020 ffffea001136e220 ffff8804664f8040 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>  ffff8804508af400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff8804508af480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>ffff8804508af500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>                                   ^
>  ffff8804508af580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff8804508af600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
>

Re: [GIT PULL] Please pull NFS client changes for Linux 4.13

[davej]

On Mon, Jul 31, 2017 at 10:35:45PM -0700, Linus Torvalds wrote:
 > On Mon, Jul 31, 2017 at 8:43 AM, davej@codemonkey.org.uk
 > <davej@codemonkey.org.uk> wrote:
 > > Another NFSv4 KASAN splat, this time from rc3.
 > >
 > > BUG: KASAN: use-after-free in nfs4_exchange_id_done+0x3d7/0x8e0 [nfsv4]
 > 
 > Ugh. It's really hard to tell what access that it - KASAN doesn't
 > actually give enough information. There's lots of 8-byte accesses
 > there in that function.
 > 
 > Any chance of getting the output from
 > 
 >    ./scripts/faddr2line vmlinux nfs4_exchange_id_done+0x3d7/0x8e0
 

Hm, that points to this..

7463                 /* Save the EXCHANGE_ID verifier session trunk tests */
7464                 memcpy(clp->cl_confirm.data, cdata->args.verifier->data,
7465                        sizeof(clp->cl_confirm.data));

	Dave

Re: [GIT PULL] Please pull NFS client changes for Linux 4.13

[Linus Torvalds]

[-- Attachment #1: Type: text/plain, Size: 2322 bytes --]

On Tue, Aug 1, 2017 at 8:51 AM, davej@codemonkey.org.uk
<davej@codemonkey.org.uk> wrote:
> On Mon, Jul 31, 2017 at 10:35:45PM -0700, Linus Torvalds wrote:
>  > Any chance of getting the output from
>  >
>  >    ./scripts/faddr2line vmlinux nfs4_exchange_id_done+0x3d7/0x8e0
>
>
> Hm, that points to this..
>
> 7463                 /* Save the EXCHANGE_ID verifier session trunk tests */
> 7464                 memcpy(clp->cl_confirm.data, cdata->args.verifier->data,
> 7465                        sizeof(clp->cl_confirm.data));

Ok, that certainly made no sense to me, because the KASAN report made
it look like a stale pathname access (allocated in getname, freed in
putname), but I think the issue is more fundamental than that.

That cdata->args.verifier seems to be entirely broken. AT least for
the "xprt == NULL" case, it does the following:

 - use the address of a local variable ("&verifier")

 - wait for the rpc completion using rpc_wait_for_completion_task().

That's unacceptably buggy crap. rpc_wait_for_completion_task() will
happily exit on a deadly signal even if the rpc hasn't been completed,
so now you'll have a stale pointer to a stack that has been freed.

So I think the 'pathname' part may actually be entirely a red herring,
and it's the underlying access itself that just picks up a random
pointer from a stack that now contains something different. And KASAN
didn't notice the stale stack access itself, because the stack slot is
still valid - it's just no longer the original 'verifier' allocation.

Or *something* like that.

None of this looks even remotely new, though - the code seems to go
back to 2009. Have you just changed what you're testing to trigger
these things?

I'm not even sure why it does that stupid stack allocation. It does a
*real* allocation just a few lines later:

        struct nfs41_exchange_id_data *calldata
        ...
        calldata = kzalloc(sizeof(*calldata), GFP_NOFS);

and the whole verifier structure could easily have been part of that
same allocation as far as I can tell.

And that really might seem to be the right thing to do.

TOTALLY UNTESTED PROBABLY COMPLETE CRAP patch attatched.

That patch compiles for me. It *might* even work. Or it might just be
the ramblings of a diseased mind.

Anna? Trond?

So caveat probatorem,

              Linus

[-- Attachment #2: patch.diff --]
[-- Type: text/plain, Size: 1904 bytes --]

 fs/nfs/nfs4proc.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 18ca6879d8de..0712af3d38f8 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -7490,6 +7490,11 @@ static const struct rpc_call_ops nfs4_exchange_id_call_ops = {
 	.rpc_release = nfs4_exchange_id_release,
 };
 
+struct verifier_and_calldata {
+	struct nfs41_exchange_id_data calldata;
+	nfs4_verifier verifier;
+};
+
 /*
  * _nfs4_proc_exchange_id()
  *
@@ -7498,7 +7503,8 @@ static const struct rpc_call_ops nfs4_exchange_id_call_ops = {
 static int _nfs4_proc_exchange_id(struct nfs_client *clp, struct rpc_cred *cred,
 			u32 sp4_how, struct rpc_xprt *xprt)
 {
-	nfs4_verifier verifier;
+	struct verifier_and_calldata *vna;
+	nfs4_verifier *verifier;
 	struct rpc_message msg = {
 		.rpc_proc = &nfs4_procedures[NFSPROC4_CLNT_EXCHANGE_ID],
 		.rpc_cred = cred,
@@ -7516,14 +7522,17 @@ static int _nfs4_proc_exchange_id(struct nfs_client *clp, struct rpc_cred *cred,
 	if (!atomic_inc_not_zero(&clp->cl_count))
 		return -EIO;
 
-	calldata = kzalloc(sizeof(*calldata), GFP_NOFS);
-	if (!calldata) {
+	vna = kzalloc(sizeof(*vna), GFP_NOFS);
+	if (!vna) {
 		nfs_put_client(clp);
 		return -ENOMEM;
 	}
+	/* kfree() of calldata will also free the verifier */
+	calldata = &vna->calldata;
+	verifier = &vna->verifier;
 
 	if (!xprt)
-		nfs4_init_boot_verifier(clp, &verifier);
+		nfs4_init_boot_verifier(clp, verifier);
 
 	status = nfs4_init_uniform_client_string(clp);
 	if (status)
@@ -7566,7 +7575,7 @@ static int _nfs4_proc_exchange_id(struct nfs_client *clp, struct rpc_cred *cred,
 				RPC_TASK_SOFT|RPC_TASK_SOFTCONN|RPC_TASK_ASYNC;
 		calldata->args.verifier = &clp->cl_confirm;
 	} else {
-		calldata->args.verifier = &verifier;
+		calldata->args.verifier = verifier;
 	}
 	calldata->args.client = clp;
 #ifdef CONFIG_NFS_V4_1_MIGRATION

Re: [GIT PULL] Please pull NFS client changes for Linux 4.13

[Trond Myklebust]

On Tue, 2017-08-01 at 10:20 -0700, Linus Torvalds wrote:
> On Tue, Aug 1, 2017 at 8:51 AM, davej@codemonkey.org.uk
> <davej@codemonkey.org.uk> wrote:
> > On Mon, Jul 31, 2017 at 10:35:45PM -0700, Linus Torvalds wrote:
> >  > Any chance of getting the output from
> >  >
> >  >    ./scripts/faddr2line vmlinux
> > nfs4_exchange_id_done+0x3d7/0x8e0
> > 
> > 
> > Hm, that points to this..
> > 
> > 7463                 /* Save the EXCHANGE_ID verifier session trunk
> > tests */
> > 7464                 memcpy(clp->cl_confirm.data, cdata-
> > >args.verifier->data,
> > 7465                        sizeof(clp->cl_confirm.data));
> 
> Ok, that certainly made no sense to me, because the KASAN report made
> it look like a stale pathname access (allocated in getname, freed in
> putname), but I think the issue is more fundamental than that.
> 
> That cdata->args.verifier seems to be entirely broken. AT least for
> the "xprt == NULL" case, it does the following:
> 
>  - use the address of a local variable ("&verifier")
> 
>  - wait for the rpc completion using rpc_wait_for_completion_task().
> 
> That's unacceptably buggy crap. rpc_wait_for_completion_task() will
> happily exit on a deadly signal even if the rpc hasn't been
> completed,
> so now you'll have a stale pointer to a stack that has been freed.
> 
> So I think the 'pathname' part may actually be entirely a red
> herring,
> and it's the underlying access itself that just picks up a random
> pointer from a stack that now contains something different. And KASAN
> didn't notice the stale stack access itself, because the stack slot
> is
> still valid - it's just no longer the original 'verifier' allocation.
> 
> Or *something* like that.
> 
> None of this looks even remotely new, though - the code seems to go
> back to 2009. Have you just changed what you're testing to trigger
> these things?
> 
> I'm not even sure why it does that stupid stack allocation. It does a
> *real* allocation just a few lines later:
> 
>         struct nfs41_exchange_id_data *calldata
>         ...
>         calldata = kzalloc(sizeof(*calldata), GFP_NOFS);
> 
> and the whole verifier structure could easily have been part of that
> same allocation as far as I can tell.
> 
> And that really might seem to be the right thing to do.
> 
> TOTALLY UNTESTED PROBABLY COMPLETE CRAP patch attatched.
> 
> That patch compiles for me. It *might* even work. Or it might just be
> the ramblings of a diseased mind.
> 
> Anna? Trond?
> 

I came to the same conclusion yesterday, and have a stable patch that
does something similar. I just got distracted with the other bugs that
were introduced by the exchangeid patch series in Linux-4.9 (including
what looks like a duplicate free issue in nfs4_test_session_trunk()).

I can pass a few of the more critical patches on to Anna for merging in
this cycle, then I've got some clean ups ready for the 4.14 merge
window.

Cheers
  Trond

-- 
Trond Myklebust
Linux NFS client maintainer, PrimaryData
trond.myklebust@primarydata.com

Re: [GIT PULL] Please pull NFS client changes for Linux 4.13

[davej]

On Tue, Aug 01, 2017 at 10:20:31AM -0700, Linus Torvalds wrote:

 > So I think the 'pathname' part may actually be entirely a red herring,
 > and it's the underlying access itself that just picks up a random
 > pointer from a stack that now contains something different. And KASAN
 > didn't notice the stale stack access itself, because the stack slot is
 > still valid - it's just no longer the original 'verifier' allocation.
 > 
 > Or *something* like that.
 > 
 > None of this looks even remotely new, though - the code seems to go
 > back to 2009. Have you just changed what you're testing to trigger
 > these things?

No idea why it only just showed up, but it isn't 100% reproducable
either.  A month or so ago I did disable the V4 code on the server
completely (as I was using v3 everywhere else), so maybe I started hitting
a fallback path somewhere.  *shrug*

	Dave

Re: [GIT PULL] Please pull NFS client changes for Linux 4.13

[Trond Myklebust]

On Tue, 2017-08-01 at 13:50 -0400, davej@codemonkey.org.uk wrote:
> On Tue, Aug 01, 2017 at 10:20:31AM -0700, Linus Torvalds wrote:
> 
>  > So I think the 'pathname' part may actually be entirely a red
> herring,
>  > and it's the underlying access itself that just picks up a random
>  > pointer from a stack that now contains something different. And
> KASAN
>  > didn't notice the stale stack access itself, because the stack
> slot is
>  > still valid - it's just no longer the original 'verifier'
> allocation.
>  > 
>  > Or *something* like that.
>  > 
>  > None of this looks even remotely new, though - the code seems to
> go
>  > back to 2009. Have you just changed what you're testing to trigger
>  > these things?
> 
> No idea why it only just showed up, but it isn't 100% reproducable
> either.  A month or so ago I did disable the V4 code on the server
> completely (as I was using v3 everywhere else), so maybe I started
> hitting
> a fallback path somewhere.  *shrug*
> 

I would only expect you too see it if you interrupt the wait on the
asynchronous EXCHANGE_ID call (which would allow the RPC call to
continue while the caller stack is trashed). Prior to commit
8d89bd70bc939, that code path was fully synchronous, so there was no
issue with interrupting the call.

-- 
Trond Myklebust
Linux NFS client maintainer, PrimaryData
trond.myklebust@primarydata.com

Re: [GIT PULL] Please pull NFS client changes for Linux 4.13

[Linus Torvalds]

On Tue, Aug 1, 2017 at 10:20 AM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> So I think the 'pathname' part may actually be entirely a red herring,
> and it's the underlying access itself that just picks up a random
> pointer from a stack that now contains something different. And KASAN
> didn't notice the stale stack access itself, because the stack slot is
> still valid - it's just no longer the original 'verifier' allocation.
>
> Or *something* like that.

I think the "something like that" is actually just reading the
cdata->args.verifier->data pointer itself, and it *is* the stack
access - but the stack page has been free'd (because of the same fatal
signal that interrupted the rpc_wait_for_completion_task() call), and
then re-allocated (and free'd again) as a pathname page.

Maybe.

Regardless, my patch still looks conceptually correct, even if it
might have bugs due to total lack of testing.

                    Linus