linux-stable.git/fs, branch v3.2.68

nilfs2: fix deadlock of segment constructor over I_SYNC flag

2015-03-06T00:39:19+00:00

commit 7ef3ff2fea8bf5e4a21cef47ad87710a3d0fdb52 upstream.

Nilfs2 eventually hangs in a stress test with fsstress program.  This
issue was caused by the following deadlock over I_SYNC flag between
nilfs_segctor_thread() and writeback_sb_inodes():

  nilfs_segctor_thread()
    nilfs_segctor_thread_construct()
      nilfs_segctor_unlock()
        nilfs_dispose_list()
          iput()
            iput_final()
              evict()
                inode_wait_for_writeback()  * wait for I_SYNC flag

  writeback_sb_inodes()
     * set I_SYNC flag on inode->i_state
    __writeback_single_inode()
      do_writepages()
        nilfs_writepages()
          nilfs_construct_dsync_segment()
            nilfs_segctor_sync()
               * wait for completion of segment constructor
    inode_sync_complete()
       * clear I_SYNC flag after __writeback_single_inode() completed

writeback_sb_inodes() calls do_writepages() for dirty inodes after
setting I_SYNC flag on inode->i_state.  do_writepages() in turn calls
nilfs_writepages(), which can run segment constructor and wait for its
completion.  On the other hand, segment constructor calls iput(), which
can call evict() and wait for the I_SYNC flag on
inode_wait_for_writeback().

Since segment constructor doesn't know when I_SYNC will be set, it
cannot know whether iput() will block or not unless inode->i_nlink has a
non-zero count.  We can prevent evict() from being called in iput() by
implementing sop->drop_inode(), but it's not preferable to leave inodes
with i_nlink == 0 for long periods because it even defers file
truncation and inode deallocation.  So, this instead resolves the
deadlock by calling iput() asynchronously with a workqueue for inodes
with i_nlink == 0.

Signed-off-by: Ryusuke Konishi 
Cc: Al Viro 
Tested-by: Ryusuke Konishi 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Ben Hutchings

splice: Apply generic position and size checks to each write

2015-02-20T00:49:41+00:00

We need to check the position and size of file writes against various
limits, using generic_write_check().  This was not being done for
the splice write path.  It was fixed upstream by commit 8d0207652cbe
("->splice_write() via ->write_iter()") but we can't apply that.

CVE-2014-7822

Signed-off-by: Ben Hutchings

vfs: Fix vfsmount_lock imbalance in path_init()

2015-02-20T00:49:41+00:00

When backporting commit 4023bfc9f351 ("be careful with nd->inode in
path_init() and follow_dotdot_rcu()"), I failed to account for the
vfsmount_lock that is used in 3.2 but not upstream.  path_init() takes
the lock if performing RCU lookup, but must drop it if (and only if)
it subsequently fails.

Reported-by: nuxi@vault24.org
References: https://bugzilla.kernel.org/show_bug.cgi?id=92531
Signed-off-by: Ben Hutchings 
Tested-by: nuxi@vault24.org

dcache: Fix locking bugs in backported "deal with deadlock in d_walk()"

2015-02-20T00:49:41+00:00

Steven Rostedt reported:
> Porting -rt to the latest 3.2 stable tree I triggered this bug:
> 
> =====================================
> [ BUG: bad unlock balance detected! ]
> -------------------------------------
> rm/1638 is trying to release lock (rcu_read_lock) at:
> [] rcu_read_unlock+0x0/0x23
> but there are no more locks to release!
> 
> other info that might help us debug this:
> 2 locks held by rm/1638:
>  #0:  (&sb->s_type->i_mutex_key#9/1){+.+.+.}, at: [] do_rmdir+0x5f/0xd2
>  #1:  (&sb->s_type->i_mutex_key#9){+.+.+.}, at: [] vfs_rmdir+0x49/0xac
> 
> stack backtrace:
> Pid: 1638, comm: rm Not tainted 3.2.66-test-rt96+ #2
> Call Trace:
>  [] ? printk+0x1d/0x1f
>  [] print_unlock_inbalance_bug+0xc3/0xcd
>  [] lock_release_non_nested+0x98/0x1ec
>  [] ? trace_hardirqs_off_caller+0x18/0x90
>  [] ? local_clock+0x2d/0x50
>  [] ? d_hash+0x2f/0x2f
>  [] ? d_hash+0x2f/0x2f
>  [] lock_release+0x192/0x1ad
>  [] rcu_read_unlock+0x17/0x23
>  [] shrink_dcache_parent+0x227/0x270
>  [] vfs_rmdir+0x68/0xac
>  [] do_rmdir+0x98/0xd2
>  [] ? fput+0x1a3/0x1ab
>  [] ? sysenter_exit+0xf/0x1a
>  [] ? trace_hardirqs_on_caller+0x118/0x149
>  [] sys_unlinkat+0x2b/0x35
>  [] sysenter_do_call+0x12/0x12
> 
> 
> 
> 
> There's a path to calling rcu_read_unlock() without calling
> rcu_read_lock() in have_submounts().
> 
> 	goto positive;
> 
> positive:
> 	if (!locked && read_seqretry(&rename_lock, seq))
> 		goto rename_retry;
> 
> rename_retry:
> 	rcu_read_unlock();
> 
> in the above path, rcu_read_lock() is never done before calling
> rcu_read_unlock();

I reviewed locking contexts in all three functions that I changed when
backporting "deal with deadlock in d_walk()".  It's actually worse
than this:

- We don't hold this_parent->d_lock at the 'positive' label in
  have_submounts(), but it is unlocked after 'rename_retry'.
- There is an rcu_read_unlock() after the 'out' label in
  select_parent(), but it's not held at the 'goto out'.

Fix all three lock imbalances.

Reported-by: Steven Rostedt 
Signed-off-by: Ben Hutchings 
Tested-by: Steven Rostedt

fsnotify: next_i is freed during fsnotify_unmount_inodes.

2015-02-20T00:49:41+00:00

commit 6424babfd68dd8a83d9c60a5242d27038856599f upstream.

During file system stress testing on 3.10 and 3.12 based kernels, the
umount command occasionally hung in fsnotify_unmount_inodes in the
section of code:

                spin_lock(&inode->i_lock);
                if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) {
                        spin_unlock(&inode->i_lock);
                        continue;
                }

As this section of code holds the global inode_sb_list_lock, eventually
the system hangs trying to acquire the lock.

Multiple crash dumps showed:

The inode->i_state == 0x60 and i_count == 0 and i_sb_list would point
back at itself.  As this is not the value of list upon entry to the
function, the kernel never exits the loop.

To help narrow down problem, the call to list_del_init in
inode_sb_list_del was changed to list_del.  This poisons the pointers in
the i_sb_list and causes a kernel to panic if it transverse a freed
inode.

Subsequent stress testing paniced in fsnotify_unmount_inodes at the
bottom of the list_for_each_entry_safe loop showing next_i had become
free.

We believe the root cause of the problem is that next_i is being freed
during the window of time that the list_for_each_entry_safe loop
temporarily releases inode_sb_list_lock to call fsnotify and
fsnotify_inode_delete.

The code in fsnotify_unmount_inodes attempts to prevent the freeing of
inode and next_i by calling __iget.  However, the code doesn't do the
__iget call on next_i

	if i_count == 0 or
	if i_state & (I_FREEING | I_WILL_FREE)

The patch addresses this issue by advancing next_i in the above two cases
until we either find a next_i which we can __iget or we reach the end of
the list.  This makes the handling of next_i more closely match the
handling of the variable "inode."

The time to reproduce the hang is highly variable (from hours to days.) We
ran the stress test on a 3.10 kernel with the proposed patch for a week
without failure.

During list_for_each_entry_safe, next_i is becoming free causing
the loop to never terminate.  Advance next_i in those cases where
__iget is not done.

Signed-off-by: Jerry Hoemann 
Cc: Jeff Kirsher 
Cc: Ken Helias 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Ben Hutchings 
Cc: Jan Kara

udf: Check component length before reading it

2015-02-20T00:49:32+00:00

commit e237ec37ec154564f8690c5bd1795339955eeef9 upstream.

Check that length specified in a component of a symlink fits in the
input buffer we are reading. Also properly ignore component length for
component types that do not use it. Otherwise we read memory after end
of buffer for corrupted udf image.

Reported-by: Carl Henrik Lunde 
Signed-off-by: Jan Kara 
Signed-off-by: Ben Hutchings

udf: Check path length when reading symlink

2015-02-20T00:49:32+00:00

commit 0e5cc9a40ada6046e6bc3bdfcd0c0d7e4b706b14 upstream.

Symlink reading code does not check whether the resulting path fits into
the page provided by the generic code. This isn't as easy as just
checking the symlink size because of various encoding conversions we
perform on path. So we have to check whether there is still enough space
in the buffer on the fly.

Reported-by: Carl Henrik Lunde 
Signed-off-by: Jan Kara 
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings

udf: Treat symlink component of type 2 as /

2015-02-20T00:49:32+00:00

commit fef2e9f3301934773e4f1b3cc5c7bffb119346b8 upstream.

Currently, we ignore symlink component of type 2. But mkisofs and other OS'
seem to treat it as / so do the same for compatibility.

Reported-by: "Gábor S." 
Signed-off-by: Jan Kara 
Signed-off-by: Ben Hutchings

udf: Verify symlink size before loading it

2015-02-20T00:49:32+00:00

commit a1d47b262952a45aae62bd49cfaf33dd76c11a2c upstream.

UDF specification allows arbitrarily large symlinks. However we support
only symlinks at most one block large. Check the length of the symlink
so that we don't access memory beyond end of the symlink block.

Reported-by: Carl Henrik Lunde 
Signed-off-by: Jan Kara 
Signed-off-by: Ben Hutchings

udf: Verify i_size when loading inode

2015-02-20T00:49:32+00:00

commit e159332b9af4b04d882dbcfe1bb0117f0a6d4b58 upstream.

Verify that inode size is sane when loading inode with data stored in
ICB. Otherwise we may get confused later when working with the inode and
inode size is too big.

Reported-by: Carl Henrik Lunde 
Signed-off-by: Jan Kara 
[bwh: Backported to 3.2: on error, call make_bad_inode() then return]
Signed-off-by: Ben Hutchings