linux.git/fs, branch v2.6.27

Don't allow splice() to files opened with O_APPEND

2008-10-09T21:26:38+00:00

This is debatable, but while we're debating it, let's disallow the
combination of splice and an O_APPEND destination.

It's not entirely clear what the semantics of O_APPEND should be, and
POSIX apparently expects pwrite() to ignore O_APPEND, for example.  So
we could make up any semantics we want, including the old ones.

But Miklos convinced me that we should at least give it some thought,
and that accepting writes at arbitrary offsets is wrong at least for
IS_APPEND() files (which always have O_APPEND set, even if the reverse
isn't true: you can obviously have O_APPEND set on a regular file).

So disallow O_APPEND entirely for now.  I doubt anybody cares, and this
way we have one less gray area to worry about.

Reported-and-argued-for-by: Miklos Szeredi 
Acked-by: Jens Axboe 
Signed-off-by: Linus Torvalds

mm: tiny-shmem nommu fix

2008-10-02T22:53:13+00:00

The previous patch db203d53d474aa068984e409d807628f5841da1b ("mm:
tiny-shmem fix lock ordering: mmap_sem vs i_mutex") to fix the lock
ordering in tiny-shmem breaks shared anonymous and IPC memory on NOMMU
architectures because it was using the expanding truncate to signal ramfs
to allocate a physically contiguous RAM backing the inode (otherwise it is
unusable for "memory mapping" it to userspace).

However do_truncate is what caused the lock ordering error, due to it
taking i_mutex.  In this case, we can actually just call ramfs directly to
allocate memory for the mapping, rather than go via truncate.

Acked-by: David Howells 
Acked-by: Hugh Dickins 
Signed-off-by: Nick Piggin 
Cc: Matt Mackall 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

inotify: fix lock ordering wrt do_page_fault's mmap_sem

2008-10-02T22:53:13+00:00

Fix inotify lock order reversal with mmap_sem due to holding locks over
copy_to_user.

Signed-off-by: Nick Piggin 
Reported-by: "Daniel J Blueman" 
Tested-by: "Daniel J Blueman" 
Cc: Ingo Molnar 
Cc: Peter Zijlstra 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm owner: fix race between swapoff and exit

2008-09-29T15:41:47+00:00

There's a race between mm->owner assignment and swapoff, more easily
seen when task slab poisoning is turned on.  The condition occurs when
try_to_unuse() runs in parallel with an exiting task.  A similar race
can occur with callers of get_task_mm(), such as /proc//
or ptrace or page migration.

CPU0                                    CPU1
                                        try_to_unuse
                                        looks at mm = task0->mm
                                        increments mm->mm_users
task 0 exits
mm->owner needs to be updated, but no
new owner is found (mm_users > 1, but
no other task has task->mm = task0->mm)
mm_update_next_owner() leaves
                                        mmput(mm) decrements mm->mm_users
task0 freed
                                        dereferencing mm->owner fails

The fix is to notify the subsystem via mm_owner_changed callback(),
if no new owner is found, by specifying the new task as NULL.

Jiri Slaby:
mm->owner was set to NULL prior to calling cgroup_mm_owner_callbacks(), but
must be set after that, so as not to pass NULL as old owner causing oops.

Daisuke Nishimura:
mm_update_next_owner() may set mm->owner to NULL, but mem_cgroup_from_task()
and its callers need to take account of this situation to avoid oops.

Hugh Dickins:
Lockdep warning and hang below exec_mmap() when testing these patches.
exit_mm() up_reads mmap_sem before calling mm_update_next_owner(),
so exec_mmap() now needs to do the same.  And with that repositioning,
there's now no point in mm_need_new_owner() allowing for NULL mm.

Reported-by: Hugh Dickins 
Signed-off-by: Balbir Singh 
Signed-off-by: Jiri Slaby 
Signed-off-by: Daisuke Nishimura 
Signed-off-by: Hugh Dickins 
Cc: KAMEZAWA Hiroyuki 
Cc: Paul Menage 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Fix NULL pointer dereference in proc_sys_compare

2008-09-29T14:42:57+00:00

The VFS interface for the 'd_compare()' is a bit special (read: 'odd'),
because it really just essentially replaces a memcmp().  The filesystem
is supposed to just compare the two names with whatever case-independent
or other function.

And when I say 'is supposed to', I obviously mean that 'procfs does odd
things, and actually looks at the dentry that we don't even pass down,
rather than just the name'.  Which results in problems, because we
actually call d_compare before we have even verified that the dentry is
still hashed at all.

And that causes a problm since the inode that procfs looks at may have
been free'd and the d_inode pointer is NULL.  procfs just assumes that
all dentries are positive, since procfs itself never generates a
negative one.  But memory pressure will still result in the dentry
getting torn down, and as it is removed by RCU, it still remains visible
on some lists - and to d_compare.

If the filesystem just did a name comparison, we wouldn't care.  And we
could just fix procfs to know about negative dentries too.  But rather
than have the low-level filesystems know about internal VFS details,
just move the check for a unhashed dentry up a bit, so that we will only
call d_compare on dentries that are still active.

The actual oops this caused didn't look like a NULL pointer dereference
because procfs did a 'container_of(inode, struct proc_inode, vfs_inode)'
to get at its internal proc_inode information from the inode pointer,
and accessed a field below the inode. So the oops would look something
like

	BUG: unable to handle kernel paging request at fffffffffffffff0
	IP: [] proc_sys_compare+0x36/0x50

and was seen on both x86-64 (Alexey Dobriyan and Hugh Dickins) and
ppc64 (Hugh Dickins).

Reported-by: Alexey Dobriyan 
Acked-by: Hugh Dickins 
Cc: Al Viro 
Reviewed-by: "Eric W. Biederman" 
Signed-of-by: Linus Torvalds

Merge git://oss.sgi.com:8090/xfs/linux-2.6

2008-09-26T15:49:34+00:00

* git://oss.sgi.com:8090/xfs/linux-2.6:
  [XFS] Remove xfs_iext_irec_compact_full()
  [XFS] Fix extent list corruption in xfs_iext_irec_compact_full().

Merge branch 'linux-next' of git://git.infradead.org/~dedekind/ubifs-2.6

2008-09-26T15:20:26+00:00

* 'linux-next' of git://git.infradead.org/~dedekind/ubifs-2.6:
  UBIFS: fix printk format warnings
  UBIFS: remove incorrect assert
  UBIFS: TNC / GC race fixes
  UBIFS: create the name of the background thread in every case

[XFS] Remove xfs_iext_irec_compact_full()

2008-09-26T02:17:57+00:00

Yet another bug was found in xfs_iext_irec_compact_full() and while the
source of the bug was found it wasn't an easy task to track it down
because the conditions are very difficult to reproduce.

A HUGE thank-you goes to Russell Cattelan and Eric Sandeen for their
significant effort in tracking down the source of this corruption.

xfs_iext_irec_compact_full() and xfs_iext_irec_compact_pages() are almost
identical - they both compact indirect extent lists by moving extents from
subsequent buffers into earlier ones. xfs_iext_irec_compact_pages() only
moves extents if all of the extents in the next buffer will fit into the
empty space in the buffer before it. xfs_iext_irec_compact_full() will go
a step further and move part of the next buffer if all the extents wont
fit. It will then shift the remaining extents in the next buffer up to the
start of the buffer. The bug here was that we did not update er_extoff and
this caused extent list corruption.

It does not appear that this extra functionality gains us much. Calling
xfs_iext_irec_compact_pages() instead will do a good enough job at
compacting the indirect list and will be quicker too.

For the case in xfs_iext_indirect_to_direct() the total number of extents
in the indirect list will fit into one buffer so we will never need the
extra functionality of xfs_iext_irec_compact_full() there.

Also xfs_iext_irec_compact_pages() doesn't need to do a memmove() (the
buffers will never overlap) so we don't want the performance hit that can
incur.

SGI-PV: 987159

SGI-Modid: xfs-linux-melb:xfs-kern:32166a

Signed-off-by: Lachlan McIlroy 
Signed-off-by: Eric Sandeen

[XFS] Fix extent list corruption in xfs_iext_irec_compact_full().

2008-09-26T02:16:46+00:00

If we don't move all the records from the next buffer into the current
buffer then we need to update the er_extoff field of the next buffer as we
shift the remaining records to the start of the buffer.

SGI-PV: 987159

SGI-Modid: xfs-linux-melb:xfs-kern:32165a

Signed-off-by: Lachlan McIlroy 
Signed-off-by: Eric Sandeen 
Signed-off-by: Russell Cattelan

9p: use an IS_ERR test rather than a NULL test

2008-09-24T21:22:22+00:00

In case of error, the function p9_client_walk returns an ERR pointer, but
never returns a NULL pointer.  So a NULL test that comes after an IS_ERR
test should be deleted.

The semantic match that finds this problem is as follows:
(http://www.emn.fr/x-info/coccinelle/)

// 
@match_bad_null_test@
expression x, E;
statement S1,S2;
@@
x = p9_client_walk(...)
... when != x = E
*  if (x != NULL)
S1 else S2
// 

Signed-off-by: Julien Brunel 
Signed-off-by: Julia Lawall 
Signed-off-by: Eric Van Hensbergen 
Signed-off-by: Andrew Morton