Skip to content

cloud-kernel
cloud-kernel

openanolis / cloud-kernel
1 年多 前同步成功

通知 161
Star 36
Fork 7
cloud-kernel
cloud-kernel
切换分支/标签
  1. 20 6月, 2017 2 次提交
  3. 19 6月, 2017 1 次提交
  5. 11 6月, 2017 1 次提交
  7. 10 6月, 2017 10 次提交
  9. 09 6月, 2017 5 次提交
  11. 05 6月, 2017 11 次提交
  13. 04 6月, 2017 1 次提交
  15. 03 6月, 2017 1 次提交
    • R
      dax: fix race between colliding PMD & PTE entries · e2093926
      由 Ross Zwisler 提交于 
      We currently have two related PMD vs PTE races in the DAX code.  These
can both be easily triggered by having two threads reading and writing
simultaneously to the same private mapping, with the key being that
private mapping reads can be handled with PMDs but private mapping
writes are always handled with PTEs so that we can COW.

Here is the first race:

  CPU 0					CPU 1

  (private mapping write)
  __handle_mm_fault()
    create_huge_pmd() - FALLBACK
    handle_pte_fault()
      passes check for pmd_devmap()

					(private mapping read)
					__handle_mm_fault()
					  create_huge_pmd()
					    dax_iomap_pmd_fault() inserts PMD

      dax_iomap_pte_fault() does a PTE fault, but we already have a DAX PMD
      			  installed in our page tables at this spot.

Here's the second race:

  CPU 0					CPU 1

  (private mapping read)
  __handle_mm_fault()
    passes check for pmd_none()
    create_huge_pmd()
      dax_iomap_pmd_fault() inserts PMD

  (private mapping write)
  __handle_mm_fault()
    create_huge_pmd() - FALLBACK
					(private mapping read)
					__handle_mm_fault()
					  passes check for pmd_none()
					  create_huge_pmd()

    handle_pte_fault()
      dax_iomap_pte_fault() inserts PTE
					    dax_iomap_pmd_fault() inserts PMD,
					       but we already have a PTE at
					       this spot.

The core of the issue is that while there is isolation between faults to
the same range in the DAX fault handlers via our DAX entry locking,
there is no isolation between faults in the code in mm/memory.c.  This
means for instance that this code in __handle_mm_fault() can run:

	if (pmd_none(*vmf.pmd) && transparent_hugepage_enabled(vma)) {
		ret = create_huge_pmd(&vmf);

But by the time we actually get to run the fault handler called by
create_huge_pmd(), the PMD is no longer pmd_none() because a racing PTE
fault has installed a normal PMD here as a parent.  This is the cause of
the 2nd race.  The first race is similar - there is the following check
in handle_pte_fault():

	} else {
		/* See comment in pte_alloc_one_map() */
		if (pmd_devmap(*vmf->pmd) || pmd_trans_unstable(vmf->pmd))
			return 0;

So if a pmd_devmap() PMD (a DAX PMD) has been installed at vmf->pmd, we
will bail and retry the fault.  This is correct, but there is nothing
preventing the PMD from being installed after this check but before we
actually get to the DAX PTE fault handlers.

In my testing these races result in the following types of errors:

  BUG: Bad rss-counter state mm:ffff8800a817d280 idx:1 val:1
  BUG: non-zero nr_ptes on freeing mm: 15

Fix this issue by having the DAX fault handlers verify that it is safe
to continue their fault after they have taken an entry lock to block
other racing faults.

[ross.zwisler@linux.intel.com: improve fix for colliding PMD & PTE entries]
  Link: http://lkml.kernel.org/r/20170526195932.32178-1-ross.zwisler@linux.intel.com
Link: http://lkml.kernel.org/r/20170522215749.23516-2-ross.zwisler@linux.intel.comSigned-off-by: NRoss Zwisler <ross.zwisler@linux.intel.com>
Reported-by: NPawel Lebioda <pawel.lebioda@intel.com>
Reviewed-by: NJan Kara <jack@suse.cz>
Cc: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Pawel Lebioda <pawel.lebioda@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Xiong Zhou <xzhou@redhat.com>
Cc: Eryu Guan <eguan@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      e2093926
  17. 02 6月, 2017 1 次提交
  19. 01 6月, 2017 3 次提交
    • J
      btrfs: fix race with relocation recovery and fs_root setup · a9b3311e
      由 Jeff Mahoney 提交于 
      If we have to recover relocation during mount, we'll ultimately have to
evict the orphan inode.  That goes through the reservation dance, where
priority_reclaim_metadata_space and flush_space expect fs_info->fs_root
to be valid.  That's the next thing to be set up during mount, so we
crash, almost always in flush_space trying to join the transaction
but priority_reclaim_metadata_space is possible as well.  This call
path has been problematic in the past WRT whether ->fs_root is valid
yet.  Commit 957780eb (Btrfs: introduce ticketed enospc
infrastructure) added new users that are called in the direct path
instead of the async path that had already been worked around.

The thing is that we don't actually need the fs_root, specifically, for
anything.  We either use it to determine whether the root is the
chunk_root for use in choosing an allocation profile or as a root to pass
btrfs_join_transaction before immediately committing it.  Anything that
isn't the chunk root works in the former case and any root works in
the latter.

A simple fix is to use a root we know will always be there: the
extent_root.

Cc: <stable@vger.kernel.org> # v4.8+
Fixes: 957780eb (Btrfs: introduce ticketed enospc infrastructure)
Signed-off-by: NJeff Mahoney <jeffm@suse.com>
Reviewed-by: NLiu Bo <bo.li.liu@oracle.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>
      a9b3311e
    • J
      btrfs: fix memory leak in update_space_info failure path · 896533a7
      由 Jeff Mahoney 提交于 
      If we fail to add the space_info kobject, we'll leak the memory
for the percpu counter.

Fixes: 6ab0a202 (btrfs: publish allocation data in sysfs)
Cc: <stable@vger.kernel.org> # v3.14+
Signed-off-by: NJeff Mahoney <jeffm@suse.com>
Reviewed-by: NLiu Bo <bo.li.liu@oracle.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>
      896533a7
    • D
      btrfs: use correct types for page indices in btrfs_page_exists_in_range · cc2b702c
      由 David Sterba 提交于 
      Variables start_idx and end_idx are supposed to hold a page index
derived from the file offsets. The int type is not the right one though,
offsets larger than 1 << 44 will get silently trimmed off the high bits.
(1 << 44 is 16TiB)

What can go wrong, if start is below the boundary and end gets trimmed:
- if there's a page after start, we'll find it (radix_tree_gang_lookup_slot)
- the final check "if (page->index <= end_idx)" will unexpectedly fail

The function will return false, ie. "there's no page in the range",
although there is at least one.

btrfs_page_exists_in_range is used to prevent races in:

* in hole punching, where we make sure there are not pages in the
  truncated range, otherwise we'll wait for them to finish and redo
  truncation, but we're going to replace the pages with holes anyway so
  the only problem is the intermediate state

* lock_extent_direct: we want to make sure there are no pages before we
  lock and start DIO, to prevent stale data reads

For practical occurence of the bug, there are several constaints.  The
file must be quite large, the affected range must cross the 16TiB
boundary and the internal state of the file pages and pending operations
must match.  Also, we must not have started any ordered data in the
range, otherwise we don't even reach the buggy function check.

DIO locking tries hard in several places to avoid deadlocks with
buffered IO and avoids waiting for ranges. The worst consequence seems
to be stale data read.

CC: Liu Bo <bo.li.liu@oracle.com>
CC: stable@vger.kernel.org	# 3.16+
Fixes: fc4adbff ("btrfs: Drop EXTENT_UPTODATE check in hole punching and direct locking")
Reviewed-by: NLiu Bo <bo.li.liu@oracle.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>
      cc2b702c
  21. 31 5月, 2017 2 次提交
    • B
      xfs: use ->b_state to fix buffer I/O accounting release race · 63db7c81
      由 Brian Foster 提交于 
      We've had user reports of unmount hangs in xfs_wait_buftarg() that
analysis shows is due to btp->bt_io_count == -1. bt_io_count
represents the count of in-flight asynchronous buffers and thus
should always be >= 0. xfs_wait_buftarg() waits for this value to
stabilize to zero in order to ensure that all untracked (with
respect to the lru) buffers have completed I/O processing before
unmount proceeds to tear down in-core data structures.

The value of -1 implies an I/O accounting decrement race. Indeed,
the fact that xfs_buf_ioacct_dec() is called from xfs_buf_rele()
(where the buffer lock is no longer held) means that bp->b_flags can
be updated from an unsafe context. While a user-level reproducer is
currently not available, some intrusive hacks to run racing buffer
lookups/ioacct/releases from multiple threads was used to
successfully manufacture this problem.

Existing callers do not expect to acquire the buffer lock from
xfs_buf_rele(). Therefore, we can not safely update ->b_flags from
this context. It turns out that we already have separate buffer
state bits and associated serialization for dealing with buffer LRU
state in the form of ->b_state and ->b_lock. Therefore, replace the
_XBF_IN_FLIGHT flag with a ->b_state variant, update the I/O
accounting wrappers appropriately and make sure they are used with
the correct locking. This ensures that buffer in-flight state can be
modified at buffer release time without racing with modifications
from a buffer lock holder.

Fixes: 9c7504aa ("xfs: track and serialize in-flight async buffers against unmount")
Cc: <stable@vger.kernel.org> # v4.8+
Signed-off-by: NBrian Foster <bfoster@redhat.com>
Reviewed-by: NNikolay Borisov <nborisov@suse.com>
Tested-by: NLibor Pechacek <lpechacek@suse.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>
      63db7c81
    • L
      "Yes, people use FOLL_FORCE ;)" · f511c0b1
      由 Linus Torvalds 提交于 
      This effectively reverts commit 8ee74a91 ("proc: try to remove use
of FOLL_FORCE entirely")

It turns out that people do depend on FOLL_FORCE for the /proc/<pid>/mem
case, and we're talking not just debuggers. Talking to the affected people, the use-cases are:

Keno Fischer:
 "We used these semantics as a hardening mechanism in the julia JIT. By
  opening /proc/self/mem and using these semantics, we could avoid
  needing RWX pages, or a dual mapping approach. We do have fallbacks to
  these other methods (though getting EIO here actually causes an assert
  in released versions - we'll updated that to make sure to take the
  fall back in that case).

  Nevertheless the /proc/self/mem approach was our favored approach
  because it a) Required an attacker to be able to execute syscalls
  which is a taller order than getting memory write and b) didn't double
  the virtual address space requirements (as a dual mapping approach
  would).

  I think in general this feature is very useful for anybody who needs
  to precisely control the execution of some other process. Various
  debuggers (gdb/lldb/rr) certainly fall into that category, but there's
  another class of such processes (wine, various emulators) which may
  want to do that kind of thing.

  Now, I suspect most of these will have the other process under ptrace
  control, so maybe allowing (same_mm || ptraced) would be ok, but at
  least for the sandbox/remote-jit use case, it would be perfectly
  reasonable to not have the jit server be a ptracer"

Robert O'Callahan:
 "We write to readonly code and data mappings via /proc/.../mem in lots
  of different situations, particularly when we're adjusting program
  state during replay to match the recorded execution.

  Like Julia, we can add workarounds, but they could be expensive."

so not only do people use FOLL_FORCE for both reads and writes, but they
use it for both the local mm and remote mm.

With these comments in mind, we likely also cannot add the "are we
actively ptracing" check either, so this keeps the new code organization
and does not do a real revert that would add back the original comment
about "Maybe we should limit FOLL_FORCE to actual ptrace users?"
Reported-by: NKeno Fischer <keno@juliacomputing.com>
Reported-by: NRobert O'Callahan <robert@ocallahan.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Eric Biederman <ebiederm@xmission.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      f511c0b1
  23. 30 5月, 2017 1 次提交
    • J
      ext4: fix fdatasync(2) after extent manipulation operations · 67a7d5f5
      由 Jan Kara 提交于 
      Currently, extent manipulation operations such as hole punch, range
zeroing, or extent shifting do not record the fact that file data has
changed and thus fdatasync(2) has a work to do. As a result if we crash
e.g. after a punch hole and fdatasync, user can still possibly see the
punched out data after journal replay. Test generic/392 fails due to
these problems.

Fix the problem by properly marking that file data has changed in these
operations.

CC: stable@vger.kernel.org
Fixes: a4bb6b64Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>
      67a7d5f5
  25. 29 5月, 2017 1 次提交