linux-toradex.git/fs/fuse, branch v3.11.4

fuse: readdir: check for slash in names

2013-09-27T00:21:59+00:00

commit efeb9e60d48f7778fdcad4a0f3ad9ea9b19e5dfd upstream.

Userspace can add names containing a slash character to the directory
listing.  Don't allow this as it could cause all sorts of trouble.

Signed-off-by: Miklos Szeredi 
Signed-off-by: Greg Kroah-Hartman

fuse: hotfix truncate_pagecache() issue

2013-09-27T00:21:59+00:00

commit 06a7c3c2781409af95000c60a5df743fd4e2f8b4 upstream.

The way how fuse calls truncate_pagecache() from fuse_change_attributes()
is completely wrong. Because, w/o i_mutex held, we never sure whether
'oldsize' and 'attr->size' are valid by the time of execution of
truncate_pagecache(inode, oldsize, attr->size). In fact, as soon as we
released fc->lock in the middle of fuse_change_attributes(), we completely
loose control of actions which may happen with given inode until we reach
truncate_pagecache. The list of potentially dangerous actions includes
mmap-ed reads and writes, ftruncate(2) and write(2) extending file size.

The typical outcome of doing truncate_pagecache() with outdated arguments
is data corruption from user point of view. This is (in some sense)
acceptable in cases when the issue is triggered by a change of the file on
the server (i.e. externally wrt fuse operation), but it is absolutely
intolerable in scenarios when a single fuse client modifies a file without
any external intervention. A real life case I discovered by fsx-linux
looked like this:

1. Shrinking ftruncate(2) comes to fuse_do_setattr(). The latter sends
FUSE_SETATTR to the server synchronously, but before getting fc->lock ...
2. fuse_dentry_revalidate() is asynchronously called. It sends FUSE_LOOKUP
to the server synchronously, then calls fuse_change_attributes(). The
latter updates i_size, releases fc->lock, but before comparing oldsize vs
attr->size..
3. fuse_do_setattr() from the first step proceeds by acquiring fc->lock and
updating attributes and i_size, but now oldsize is equal to
outarg.attr.size because i_size has just been updated (step 2). Hence,
fuse_do_setattr() returns w/o calling truncate_pagecache().
4. As soon as ftruncate(2) completes, the user extends file size by
write(2) making a hole in the middle of file, then reads data from the hole
either by read(2) or mmap-ed read. The user expects to get zero data from
the hole, but gets stale data because truncate_pagecache() is not executed
yet.

The scenario above illustrates one side of the problem: not truncating the
page cache even though we should. Another side corresponds to truncating
page cache too late, when the state of inode changed significantly.
Theoretically, the following is possible:

1. As in the previous scenario fuse_dentry_revalidate() discovered that
i_size changed (due to our own fuse_do_setattr()) and is going to call
truncate_pagecache() for some 'new_size' it believes valid right now. But
by the time that particular truncate_pagecache() is called ...
2. fuse_do_setattr() returns (either having called truncate_pagecache() or
not -- it doesn't matter).
3. The file is extended either by write(2) or ftruncate(2) or fallocate(2).
4. mmap-ed write makes a page in the extended region dirty.

The result will be the lost of data user wrote on the fourth step.

The patch is a hotfix resolving the issue in a simplistic way: let's skip
dangerous i_size update and truncate_pagecache if an operation changing
file size is in progress. This simplistic approach looks correct for the
cases w/o external changes. And to handle them properly, more sophisticated
and intrusive techniques (e.g. NFS-like one) would be required. I'd like to
postpone it until the issue is well discussed on the mailing list(s).

Changed in v2:
 - improved patch description to cover both sides of the issue.

Signed-off-by: Maxim Patlasov 
Signed-off-by: Miklos Szeredi 
Signed-off-by: Greg Kroah-Hartman

fuse: invalidate inode attributes on xattr modification

2013-09-27T00:21:59+00:00

commit d331a415aef98717393dda0be69b7947da08eba3 upstream.

Calls like setxattr and removexattr result in updation of ctime.
Therefore invalidate inode attributes to force a refresh.

Signed-off-by: Anand Avati 
Reviewed-by: Brian Foster 
Signed-off-by: Miklos Szeredi 
Signed-off-by: Greg Kroah-Hartman

fuse: postpone end_page_writeback() in fuse_writepage_locked()

2013-09-27T00:21:59+00:00

commit 4a4ac4eba1010ef9a804569058ab29e3450c0315 upstream.

The patch fixes a race between ftruncate(2), mmap-ed write and write(2):

1) An user makes a page dirty via mmap-ed write.
2) The user performs shrinking truncate(2) intended to purge the page.
3) Before fuse_do_setattr calls truncate_pagecache, the page goes to
   writeback. fuse_writepage_locked fills FUSE_WRITE request and releases
   the original page by end_page_writeback.
4) fuse_do_setattr() completes and successfully returns. Since now, i_mutex
   is free.
5) Ordinary write(2) extends i_size back to cover the page. Note that
   fuse_send_write_pages do wait for fuse writeback, but for another
   page->index.
6) fuse_writepage_locked proceeds by queueing FUSE_WRITE request.
   fuse_send_writepage is supposed to crop inarg->size of the request,
   but it doesn't because i_size has already been extended back.

Moving end_page_writeback to the end of fuse_writepage_locked fixes the
race because now the fact that truncate_pagecache is successfully returned
infers that fuse_writepage_locked has already called end_page_writeback.
And this, in turn, infers that fuse_flush_writepages has already called
fuse_send_writepage, and the latter used valid (shrunk) i_size. write(2)
could not extend it because of i_mutex held by ftruncate(2).

Signed-off-by: Maxim Patlasov 
Signed-off-by: Miklos Szeredi 
Signed-off-by: Greg Kroah-Hartman

fuse: readdirplus: cleanup

2013-07-17T12:53:54+00:00

Niels noted that we don't need the 'dentry = NULL' line.

Signed-off-by: Miklos Szeredi 
CC: Niels de Vos

fuse: readdirplus: change attributes once

2013-07-17T12:53:53+00:00

If we got the inode through fuse_iget() then the attributes are already
up-to-date.

Signed-off-by: Miklos Szeredi

fuse: readdirplus: fix instantiate

2013-07-17T12:53:53+00:00

Fuse does instantiation slightly differently from NFS/CIFS which use
d_materialise_unique().

Signed-off-by: Miklos Szeredi 
CC: stable@vger.kernel.org

fuse: readdirplus: sanity checks

2013-07-17T12:53:53+00:00

Add sanity checks before adding or updating an entry with data received
from readdirplus.

Signed-off-by: Miklos Szeredi 
CC: stable@vger.kernel.org

fuse: readdirplus: fix dentry leak

2013-07-17T12:53:53+00:00

In case d_lookup() returns a dentry with d_inode == NULL, the dentry is not
returned with dput(). This results in triggering a BUG() in
shrink_dcache_for_umount_subtree():

  BUG: Dentry ...{i=0,n=...} still in use (1) [unmount of fuse fuse]

[SzM: need to d_drop() as well]

Reported-by: Justin Clift 
Signed-off-by: Niels de Vos 
Signed-off-by: Miklos Szeredi 
Tested-by: Brian Foster 
Tested-by: Niels de Vos 
CC: stable@vger.kernel.org

mm: use totalram_pages instead of num_physpages at runtime

2013-07-03T23:07:35+00:00

The global variable num_physpages is scheduled to be removed, so use
totalram_pages instead of num_physpages at runtime.

Signed-off-by: Jiang Liu 
Cc: Miklos Szeredi 
Cc: "David S. Miller" 
Cc: Alexey Kuznetsov 
Cc: James Morris 
Cc: Hideaki YOSHIFUJI 
Cc: Patrick McHardy 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds