UBIFS: fix an mmap and fsync race condition

There is a race condition in UBIFS:

Thread A (mmap)                        Thread B (fsync)

->__do_fault                           ->write_cache_pages
   -> ubifs_vm_page_mkwrite
       -> budget_space
       -> lock_page
       -> release/convert_page_budget
       -> SetPagePrivate
       -> TestSetPageDirty
       -> unlock_page
                                       -> lock_page
                                           -> TestClearPageDirty
                                           -> ubifs_writepage
                                               -> do_writepage
                                                   -> release_budget
                                                   -> ClearPagePrivate
                                                   -> unlock_page
   -> !(ret & VM_FAULT_LOCKED)
   -> lock_page
   -> set_page_dirty
       -> ubifs_set_page_dirty
           -> TestSetPageDirty (set page dirty without budgeting)
   -> unlock_page

This leads to situation where we have a diry page but no budget allocated for
this page, so further write-back may fail with -ENOSPC.

In this fix we return from page_mkwrite without performing unlock_page. We
return VM_FAULT_LOCKED instead. After doing this, the race above will not
happen.

Signed-off-by: hujianyang <hujianyang@huawei.com>
Tested-by: Laurence Withers <lwithers@guralp.com>
Cc: stable@vger.kernel.org
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
UBI: weaken the 'exclusive' constraint when opening volumes to rename

The UBI volume rename ioctl (UBI_IOCRNVOL) open the volumes in exclusive
mode. The volumes are opened for two reasons: to build a volume rename list,
and a volume remove list.

However, the first open constraint is excessive and can be replaced by
a 'read-write' open mode. The second open constraint is properly set as
'exclusive' given the volume is opened for removal and we don't want any
users around.

By weakening the former 'exclusive' mode, we allow 'read-only' users to keep
the volume open, while a rename is taking place. This is useful to perform
an atomic rename, in a firmware upgrade scenario, while keeping the volume
in read-only use (for instance, if a ubiblock is mounted as rootfs).

It's worth mention this is not the case of UBIFS, which keeps the volume
opened as 'read-write' despite mounted as read-write or read-only mode.

This change was suggested at least twice by Artem:
http://lists.infradead.org/pipermail/linux-mtd/2012-September/044175.html
http://permalink.gmane.org/gmane.linux.drivers.mtd/39866

Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
UBIFS: Remove unused variables in ubifs_budget_space

I found two variables in ubifs_budget_space declared but not
use. This state remains since the first commit 1e5176. So just
remove them.

Signed-off-by: hujianyang <hujianyang@huawei.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
UBI: fix rb_tree node comparison in add_map

The comparisons used in add_vol() shouldn't be identical.  Pretty sure
the following is correct but it is completely untested.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
UBIFS: Fix dump messages in ubifs_dump_lprops

Function ubifs_read_one_lp will not set @lp and returns
an error when ubifs_read_one_lp failed. We should not
perform ubifs_dump_lprop in this case because @lp is not
initialized as we wanted.

Signed-off-by: hujianyang <hujianyang@huawei.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
UBI: block: Fix error path on alloc_workqueue failure

Otherwise we'd return a random value if allocation of the workqueue fails.

Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>
Acked-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
UBIFS: add missing ui pointer in debugging code

If UBIFS_DEBUG is defined an additional assertion of the ui_lock
spinlock in do_writepage cannot compile because the ui pointer has not
been previously declared.

Fix this by declaring and initializing the ui pointer in case
UBIFS_DEBUG is defined.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
UBIFS: fix debugging check

The debugging check which verifies that we never write outside of the file
length was incorrect, since it was multiplying file length by the page size,
instead of dividing. Fix this.

Spotted-by: hujianyang <hujianyang@huawei.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
UBIFS: Remove incorrect assertion in shrink_tnc()

I hit the same assert failed as Dolev Raviv reported in Kernel v3.10
shows like this:

[ 9641.164028] UBIFS assert failed in shrink_tnc at 131 (pid 13297)
[ 9641.234078] CPU: 1 PID: 13297 Comm: mmap.test Tainted: G           O 3.10.40 #1
[ 9641.234116] [<c0011a6c>] (unwind_backtrace+0x0/0x12c) from [<c000d0b0>] (show_stack+0x20/0x24)
[ 9641.234137] [<c000d0b0>] (show_stack+0x20/0x24) from [<c0311134>] (dump_stack+0x20/0x28)
[ 9641.234188] [<c0311134>] (dump_stack+0x20/0x28) from [<bf22425c>] (shrink_tnc_trees+0x25c/0x350 [ubifs])
[ 9641.234265] [<bf22425c>] (shrink_tnc_trees+0x25c/0x350 [ubifs]) from [<bf2245ac>] (ubifs_shrinker+0x25c/0x310 [ubifs])
[ 9641.234307] [<bf2245ac>] (ubifs_shrinker+0x25c/0x310 [ubifs]) from [<c00cdad8>] (shrink_slab+0x1d4/0x2f8)
[ 9641.234327] [<c00cdad8>] (shrink_slab+0x1d4/0x2f8) from [<c00d03d0>] (do_try_to_free_pages+0x300/0x544)
[ 9641.234344] [<c00d03d0>] (do_try_to_free_pages+0x300/0x544) from [<c00d0a44>] (try_to_free_pages+0x2d0/0x398)
[ 9641.234363] [<c00d0a44>] (try_to_free_pages+0x2d0/0x398) from [<c00c6a60>] (__alloc_pages_nodemask+0x494/0x7e8)
[ 9641.234382] [<c00c6a60>] (__alloc_pages_nodemask+0x494/0x7e8) from [<c00f62d8>] (new_slab+0x78/0x238)
[ 9641.234400] [<c00f62d8>] (new_slab+0x78/0x238) from [<c031081c>] (__slab_alloc.constprop.42+0x1a4/0x50c)
[ 9641.234419] [<c031081c>] (__slab_alloc.constprop.42+0x1a4/0x50c) from [<c00f80e8>] (kmem_cache_alloc_trace+0x54/0x188)
[ 9641.234459] [<c00f80e8>] (kmem_cache_alloc_trace+0x54/0x188) from [<bf227908>] (do_readpage+0x168/0x468 [ubifs])
[ 9641.234553] [<bf227908>] (do_readpage+0x168/0x468 [ubifs]) from [<bf2296a0>] (ubifs_readpage+0x424/0x464 [ubifs])
[ 9641.234606] [<bf2296a0>] (ubifs_readpage+0x424/0x464 [ubifs]) from [<c00c17c0>] (filemap_fault+0x304/0x418)
[ 9641.234638] [<c00c17c0>] (filemap_fault+0x304/0x418) from [<c00de694>] (__do_fault+0xd4/0x530)
[ 9641.234665] [<c00de694>] (__do_fault+0xd4/0x530) from [<c00e10c0>] (handle_pte_fault+0x480/0xf54)
[ 9641.234690] [<c00e10c0>] (handle_pte_fault+0x480/0xf54) from [<c00e2bf8>] (handle_mm_fault+0x140/0x184)
[ 9641.234716] [<c00e2bf8>] (handle_mm_fault+0x140/0x184) from [<c0316688>] (do_page_fault+0x150/0x3ac)
[ 9641.234737] [<c0316688>] (do_page_fault+0x150/0x3ac) from [<c000842c>] (do_DataAbort+0x3c/0xa0)
[ 9641.234759] [<c000842c>] (do_DataAbort+0x3c/0xa0) from [<c0314e38>] (__dabt_usr+0x38/0x40)

After analyzing the code, I found a condition that may cause this failed
in correct operations. Thus, I think this assertion is wrong and should be
removed.

Suppose there are two clean znodes and one dirty znode in TNC. So the
per-filesystem atomic_t @clean_zn_cnt is (2). If commit start, dirty_znode
is set to COW_ZNODE in get_znodes_to_commit() in case of potentially ops
on this znode. We clear COW bit and DIRTY bit in write_index() without
@tnc_mutex locked. We don't increase @clean_zn_cnt in this place. As the
comments in write_index() shows, if another process hold @tnc_mutex and
dirty this znode after we clean it, @clean_zn_cnt would be decreased to (1).
We will increase @clean_zn_cnt to (2) with @tnc_mutex locked in
free_obsolete_znodes() to keep it right.

If shrink_tnc() performs between decrease and increase, it will release
other 2 clean znodes it holds and found @clean_zn_cnt is less than zero
(1 - 2 = -1), then hit the assertion. Because free_obsolete_znodes() will
soon correct @clean_zn_cnt and no harm to fs in this case, I think this
assertion could be removed.

2 clean zondes and 1 dirty znode, @clean_zn_cnt == 2

Thread A (commit)         Thread B (write or others)       Thread C (shrinker)
->write_index
   ->clear_bit(DIRTY_NODE)
   ->clear_bit(COW_ZNODE)

            @clean_zn_cnt == 2
                          ->mutex_locked(&tnc_mutex)
                          ->dirty_cow_znode
                              ->!ubifs_zn_cow(znode)
                              ->!test_and_set_bit(DIRTY_NODE)
                              ->atomic_dec(&clean_zn_cnt)
                          ->mutex_unlocked(&tnc_mutex)

            @clean_zn_cnt == 1
                                                           ->mutex_locked(&tnc_mutex)
                                                           ->shrink_tnc
                                                             ->destroy_tnc_subtree
                                                             ->atomic_sub(&clean_zn_cnt, 2)
                                                             ->ubifs_assert  <- hit
                                                           ->mutex_unlocked(&tnc_mutex)

            @clean_zn_cnt == -1
->mutex_lock(&tnc_mutex)
->free_obsolete_znodes
   ->atomic_inc(&clean_zn_cnt)
->mutux_unlock(&tnc_mutex)

            @clean_zn_cnt == 0 (correct after shrink)

Signed-off-by: hujianyang <hujianyang@huawei.com>
Cc: stable@vger.kernel.org
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
UBIFS: respect MS_SILENT mount flag

When attempting to mount a non-ubifs formatted volume, lots of error
messages (including a stack dump) are thrown to the kernel log even if
the MS_SILENT mount flag is set.
Fix this by introducing adding an additional state-variable in
struct ubifs_info and suppress error messages in ubifs_read_node if
MS_SILENT is set.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
UBIFS: Add an assertion for clean_zn_cnt

This patch adds a new ubifs_assert() in ubifs_tnc_close() to check
if there are any leaks of per-filesystem @clean_zn_cnt. This new
assert inspects whether the return value of ubifs_destroy_tnc_subtree()
is equal to @clean_zn_cnt or not while umount.

Artem: a minor amendment

Signed-off-by: hujianyang <hujianyang@huawei.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
auditsc: audit_krule mask accesses need bounds checking

Fixes an easy DoS and possible information disclosure.

This does nothing about the broken state of x32 auditing.

eparis: If the admin has enabled auditd and has specifically loaded
audit rules.  This bug has been around since before git.  Wow...

Cc: stable@vger.kernel.org
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Merge tag 'upstream-3.16-rc1-v2' of git://git.infradead.org/linux-ubifs

Pull UBIFS updates from Artem Bityutskiy:
 "This contains several UBIFS fixes.  One of them fixes a race condition
  between the mmap page fault path and fsync.  Another just removes a
  bogus assertion from the UBIFS memory shrinker.

  UBIFS also started honoring the MS_SILENT mount flag, so now it won't
  print many I/O errors when user-space just tries to probe for the FS.

  Rest of the changes are rather minor UBI/UBIFS fixes, improvements,
  and clean-ups"

* tag 'upstream-3.16-rc1-v2' of git://git.infradead.org/linux-ubifs:
  UBIFS: Add an assertion for clean_zn_cnt
  UBIFS: respect MS_SILENT mount flag
  UBIFS: Remove incorrect assertion in shrink_tnc()
  UBIFS: fix debugging check
  UBIFS: add missing ui pointer in debugging code
  UBI: block: Fix error path on alloc_workqueue failure
  UBIFS: Fix dump messages in ubifs_dump_lprops
  UBI: fix rb_tree node comparison in add_map
  UBIFS: Remove unused variables in ubifs_budget_space
  UBI: weaken the 'exclusive' constraint when opening volumes to rename
  UBIFS: fix an mmap and fsync race condition