linux-toradex.git/fs/fuse, branch v3.10.13

fuse: readdir: check for slash in names

2013-09-27T00:18:30+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

2013-09-27T00:18:30+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The typical outcome of doing truncate_pagecache() with outdated arguments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

2013-09-27T00:18:30+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()

2013-09-27T00:18:30+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: sanity checks

2013-07-28T23:30:08+00:00

commit a28ef45cbb1e7fadd5159deb17b02de15c6e4aaf upstream.

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

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

fuse: readdirplus: fix instantiate

2013-07-28T23:30:07+00:00

commit 2914941e3178d84a216fc4eb85292dfef3b6d628 upstream.

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

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

fuse: readdirplus: fix dentry leak

2013-07-28T23:30:07+00:00

commit 53ce9a3364de0723b27d861de93bfc882f7db050 upstream.

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 
Signed-off-by: Greg Kroah-Hartman

fuse: hold i_mutex in fuse_file_fallocate()

2013-06-17T23:39:03+00:00

Changing size of a file on server and local update (fuse_write_update_size)
should be always protected by inode->i_mutex. Otherwise a race like this is
possible:

1. Process 'A' calls fallocate(2) to extend file (~FALLOC_FL_KEEP_SIZE).
fuse_file_fallocate() sends FUSE_FALLOCATE request to the server.
2. Process 'B' calls ftruncate(2) shrinking the file. fuse_do_setattr()
sends shrinking FUSE_SETATTR request to the server and updates local i_size
by i_size_write(inode, outarg.attr.size).
3. Process 'A' resumes execution of fuse_file_fallocate() and calls
fuse_write_update_size(inode, offset + length). But 'offset + length' was
obsoleted by ftruncate from previous step.

Changed in v2 (thanks Brian and Anand for suggestions):
 - made relation between mutex_lock() and fuse_set_nowrite(inode) more
   explicit and clear.
 - updated patch description to use ftruncate(2) in example

Signed-off-by: Maxim V. Patlasov 
Reviewed-by: Brian Foster 
Signed-off-by: Miklos Szeredi

fuse: fix alignment in short read optimization for async_dio

2013-06-03T13:15:42+00:00

The bug was introduced with async_dio feature: trying to optimize short reads,
we cut number-of-bytes-to-read to i_size boundary. Hence the following example:

	truncate --size=300 /mnt/file
	dd if=/mnt/file of=/dev/null iflag=direct

led to FUSE_READ request of 300 bytes size. This turned out to be problem
for userspace fuse implementations who rely on assumption that kernel fuse
does not change alignment of request from client FS.

The patch turns off the optimization if async_dio is disabled. And, if it's
enabled, the patch fixes adjustment of number-of-bytes-to-read to preserve
alignment.

Note, that we cannot throw out short read optimization entirely because
otherwise a direct read of a huge size issued on a tiny file would generate
a huge amount of fuse requests and most of them would be ACKed by userspace
with zero bytes read.

Signed-off-by: Maxim Patlasov 
Reviewed-by: Brian Foster 
Signed-off-by: Miklos Szeredi

fuse: return -EIOCBQUEUED from fuse_direct_IO() for all async requests

2013-06-03T13:15:42+00:00

If request submission fails for an async request (i.e.,
get_user_pages() returns -ERESTARTSYS), we currently skip the
-EIOCBQUEUED return and drop into wait_for_sync_kiocb() forever.

Avoid this by always returning -EIOCBQUEUED for async requests. If
an error occurs, the error is passed into fuse_aio_complete(),
returned via aio_complete() and thus propagated to userspace via
io_getevents().

Signed-off-by: Brian Foster 
Reviewed-by: Maxim Patlasov 
Signed-off-by: Miklos Szeredi