<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux.git/fs/sysv, branch v3.15</title>
<subtitle>Clone of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git</subtitle>
<link rel='alternate' type='text/html' href='https://git.exis.tech/linux.git/'/>
<entry>
<title>Merge tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4</title>
<updated>2014-04-04T22:39:39+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2014-04-04T22:39:39+00:00</published>
<link rel='alternate' type='text/html' href='https://git.exis.tech/linux.git/commit/?id=24e7ea3bea94fe05eae5019f5f12bcdc98fc5157'/>
<id>24e7ea3bea94fe05eae5019f5f12bcdc98fc5157</id>
<content type='text'>
Pull ext4 updates from Ted Ts'o:
 "Major changes for 3.14 include support for the newly added ZERO_RANGE
  and COLLAPSE_RANGE fallocate operations, and scalability improvements
  in the jbd2 layer and in xattr handling when the extended attributes
  spill over into an external block.

  Other than that, the usual clean ups and minor bug fixes"

* tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4: (42 commits)
  ext4: fix premature freeing of partial clusters split across leaf blocks
  ext4: remove unneeded test of ret variable
  ext4: fix comment typo
  ext4: make ext4_block_zero_page_range static
  ext4: atomically set inode-&gt;i_flags in ext4_set_inode_flags()
  ext4: optimize Hurd tests when reading/writing inodes
  ext4: kill i_version support for Hurd-castrated file systems
  ext4: each filesystem creates and uses its own mb_cache
  fs/mbcache.c: doucple the locking of local from global data
  fs/mbcache.c: change block and index hash chain to hlist_bl_node
  ext4: Introduce FALLOC_FL_ZERO_RANGE flag for fallocate
  ext4: refactor ext4_fallocate code
  ext4: Update inode i_size after the preallocation
  ext4: fix partial cluster handling for bigalloc file systems
  ext4: delete path dealloc code in ext4_ext_handle_uninitialized_extents
  ext4: only call sync_filesystm() when remounting read-only
  fs: push sync_filesystem() down to the file system's remount_fs()
  jbd2: improve error messages for inconsistent journal heads
  jbd2: minimize region locked by j_list_lock in jbd2_journal_forget()
  jbd2: minimize region locked by j_list_lock in journal_get_create_access()
  ...
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull ext4 updates from Ted Ts'o:
 "Major changes for 3.14 include support for the newly added ZERO_RANGE
  and COLLAPSE_RANGE fallocate operations, and scalability improvements
  in the jbd2 layer and in xattr handling when the extended attributes
  spill over into an external block.

  Other than that, the usual clean ups and minor bug fixes"

* tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4: (42 commits)
  ext4: fix premature freeing of partial clusters split across leaf blocks
  ext4: remove unneeded test of ret variable
  ext4: fix comment typo
  ext4: make ext4_block_zero_page_range static
  ext4: atomically set inode-&gt;i_flags in ext4_set_inode_flags()
  ext4: optimize Hurd tests when reading/writing inodes
  ext4: kill i_version support for Hurd-castrated file systems
  ext4: each filesystem creates and uses its own mb_cache
  fs/mbcache.c: doucple the locking of local from global data
  fs/mbcache.c: change block and index hash chain to hlist_bl_node
  ext4: Introduce FALLOC_FL_ZERO_RANGE flag for fallocate
  ext4: refactor ext4_fallocate code
  ext4: Update inode i_size after the preallocation
  ext4: fix partial cluster handling for bigalloc file systems
  ext4: delete path dealloc code in ext4_ext_handle_uninitialized_extents
  ext4: only call sync_filesystm() when remounting read-only
  fs: push sync_filesystem() down to the file system's remount_fs()
  jbd2: improve error messages for inconsistent journal heads
  jbd2: minimize region locked by j_list_lock in jbd2_journal_forget()
  jbd2: minimize region locked by j_list_lock in journal_get_create_access()
  ...
</pre>
</div>
</content>
</entry>
<entry>
<title>mm + fs: store shadow entries in page cache</title>
<updated>2014-04-03T23:21:01+00:00</updated>
<author>
<name>Johannes Weiner</name>
<email>hannes@cmpxchg.org</email>
</author>
<published>2014-04-03T21:47:49+00:00</published>
<link rel='alternate' type='text/html' href='https://git.exis.tech/linux.git/commit/?id=91b0abe36a7b2b3b02d7500925a5f8455334f0e5'/>
<id>91b0abe36a7b2b3b02d7500925a5f8455334f0e5</id>
<content type='text'>
Reclaim will be leaving shadow entries in the page cache radix tree upon
evicting the real page.  As those pages are found from the LRU, an
iput() can lead to the inode being freed concurrently.  At this point,
reclaim must no longer install shadow pages because the inode freeing
code needs to ensure the page tree is really empty.

Add an address_space flag, AS_EXITING, that the inode freeing code sets
under the tree lock before doing the final truncate.  Reclaim will check
for this flag before installing shadow pages.

Signed-off-by: Johannes Weiner &lt;hannes@cmpxchg.org&gt;
Reviewed-by: Rik van Riel &lt;riel@redhat.com&gt;
Reviewed-by: Minchan Kim &lt;minchan@kernel.org&gt;
Cc: Andrea Arcangeli &lt;aarcange@redhat.com&gt;
Cc: Bob Liu &lt;bob.liu@oracle.com&gt;
Cc: Christoph Hellwig &lt;hch@infradead.org&gt;
Cc: Dave Chinner &lt;david@fromorbit.com&gt;
Cc: Greg Thelen &lt;gthelen@google.com&gt;
Cc: Hugh Dickins &lt;hughd@google.com&gt;
Cc: Jan Kara &lt;jack@suse.cz&gt;
Cc: KOSAKI Motohiro &lt;kosaki.motohiro@jp.fujitsu.com&gt;
Cc: Luigi Semenzato &lt;semenzato@google.com&gt;
Cc: Mel Gorman &lt;mgorman@suse.de&gt;
Cc: Metin Doslu &lt;metin@citusdata.com&gt;
Cc: Michel Lespinasse &lt;walken@google.com&gt;
Cc: Ozgun Erdogan &lt;ozgun@citusdata.com&gt;
Cc: Peter Zijlstra &lt;peterz@infradead.org&gt;
Cc: Roman Gushchin &lt;klamm@yandex-team.ru&gt;
Cc: Ryan Mallon &lt;rmallon@gmail.com&gt;
Cc: Tejun Heo &lt;tj@kernel.org&gt;
Cc: Vlastimil Babka &lt;vbabka@suse.cz&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Reclaim will be leaving shadow entries in the page cache radix tree upon
evicting the real page.  As those pages are found from the LRU, an
iput() can lead to the inode being freed concurrently.  At this point,
reclaim must no longer install shadow pages because the inode freeing
code needs to ensure the page tree is really empty.

Add an address_space flag, AS_EXITING, that the inode freeing code sets
under the tree lock before doing the final truncate.  Reclaim will check
for this flag before installing shadow pages.

Signed-off-by: Johannes Weiner &lt;hannes@cmpxchg.org&gt;
Reviewed-by: Rik van Riel &lt;riel@redhat.com&gt;
Reviewed-by: Minchan Kim &lt;minchan@kernel.org&gt;
Cc: Andrea Arcangeli &lt;aarcange@redhat.com&gt;
Cc: Bob Liu &lt;bob.liu@oracle.com&gt;
Cc: Christoph Hellwig &lt;hch@infradead.org&gt;
Cc: Dave Chinner &lt;david@fromorbit.com&gt;
Cc: Greg Thelen &lt;gthelen@google.com&gt;
Cc: Hugh Dickins &lt;hughd@google.com&gt;
Cc: Jan Kara &lt;jack@suse.cz&gt;
Cc: KOSAKI Motohiro &lt;kosaki.motohiro@jp.fujitsu.com&gt;
Cc: Luigi Semenzato &lt;semenzato@google.com&gt;
Cc: Mel Gorman &lt;mgorman@suse.de&gt;
Cc: Metin Doslu &lt;metin@citusdata.com&gt;
Cc: Michel Lespinasse &lt;walken@google.com&gt;
Cc: Ozgun Erdogan &lt;ozgun@citusdata.com&gt;
Cc: Peter Zijlstra &lt;peterz@infradead.org&gt;
Cc: Roman Gushchin &lt;klamm@yandex-team.ru&gt;
Cc: Ryan Mallon &lt;rmallon@gmail.com&gt;
Cc: Tejun Heo &lt;tj@kernel.org&gt;
Cc: Vlastimil Babka &lt;vbabka@suse.cz&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>fs: push sync_filesystem() down to the file system's remount_fs()</title>
<updated>2014-03-13T14:14:33+00:00</updated>
<author>
<name>Theodore Ts'o</name>
<email>tytso@mit.edu</email>
</author>
<published>2014-03-13T14:14:33+00:00</published>
<link rel='alternate' type='text/html' href='https://git.exis.tech/linux.git/commit/?id=02b9984d640873b7b3809e63f81a0d7e13496886'/>
<id>02b9984d640873b7b3809e63f81a0d7e13496886</id>
<content type='text'>
Previously, the no-op "mount -o mount /dev/xxx" operation when the
file system is already mounted read-write causes an implied,
unconditional syncfs().  This seems pretty stupid, and it's certainly
documented or guaraunteed to do this, nor is it particularly useful,
except in the case where the file system was mounted rw and is getting
remounted read-only.

However, it's possible that there might be some file systems that are
actually depending on this behavior.  In most file systems, it's
probably fine to only call sync_filesystem() when transitioning from
read-write to read-only, and there are some file systems where this is
not needed at all (for example, for a pseudo-filesystem or something
like romfs).

Signed-off-by: "Theodore Ts'o" &lt;tytso@mit.edu&gt;
Cc: linux-fsdevel@vger.kernel.org
Cc: Christoph Hellwig &lt;hch@infradead.org&gt;
Cc: Artem Bityutskiy &lt;dedekind1@gmail.com&gt;
Cc: Adrian Hunter &lt;adrian.hunter@intel.com&gt;
Cc: Evgeniy Dushistov &lt;dushistov@mail.ru&gt;
Cc: Jan Kara &lt;jack@suse.cz&gt;
Cc: OGAWA Hirofumi &lt;hirofumi@mail.parknet.co.jp&gt;
Cc: Anders Larsen &lt;al@alarsen.net&gt;
Cc: Phillip Lougher &lt;phillip@squashfs.org.uk&gt;
Cc: Kees Cook &lt;keescook@chromium.org&gt;
Cc: Mikulas Patocka &lt;mikulas@artax.karlin.mff.cuni.cz&gt;
Cc: Petr Vandrovec &lt;petr@vandrovec.name&gt;
Cc: xfs@oss.sgi.com
Cc: linux-btrfs@vger.kernel.org
Cc: linux-cifs@vger.kernel.org
Cc: samba-technical@lists.samba.org
Cc: codalist@coda.cs.cmu.edu
Cc: linux-ext4@vger.kernel.org
Cc: linux-f2fs-devel@lists.sourceforge.net
Cc: fuse-devel@lists.sourceforge.net
Cc: cluster-devel@redhat.com
Cc: linux-mtd@lists.infradead.org
Cc: jfs-discussion@lists.sourceforge.net
Cc: linux-nfs@vger.kernel.org
Cc: linux-nilfs@vger.kernel.org
Cc: linux-ntfs-dev@lists.sourceforge.net
Cc: ocfs2-devel@oss.oracle.com
Cc: reiserfs-devel@vger.kernel.org
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Previously, the no-op "mount -o mount /dev/xxx" operation when the
file system is already mounted read-write causes an implied,
unconditional syncfs().  This seems pretty stupid, and it's certainly
documented or guaraunteed to do this, nor is it particularly useful,
except in the case where the file system was mounted rw and is getting
remounted read-only.

However, it's possible that there might be some file systems that are
actually depending on this behavior.  In most file systems, it's
probably fine to only call sync_filesystem() when transitioning from
read-write to read-only, and there are some file systems where this is
not needed at all (for example, for a pseudo-filesystem or something
like romfs).

Signed-off-by: "Theodore Ts'o" &lt;tytso@mit.edu&gt;
Cc: linux-fsdevel@vger.kernel.org
Cc: Christoph Hellwig &lt;hch@infradead.org&gt;
Cc: Artem Bityutskiy &lt;dedekind1@gmail.com&gt;
Cc: Adrian Hunter &lt;adrian.hunter@intel.com&gt;
Cc: Evgeniy Dushistov &lt;dushistov@mail.ru&gt;
Cc: Jan Kara &lt;jack@suse.cz&gt;
Cc: OGAWA Hirofumi &lt;hirofumi@mail.parknet.co.jp&gt;
Cc: Anders Larsen &lt;al@alarsen.net&gt;
Cc: Phillip Lougher &lt;phillip@squashfs.org.uk&gt;
Cc: Kees Cook &lt;keescook@chromium.org&gt;
Cc: Mikulas Patocka &lt;mikulas@artax.karlin.mff.cuni.cz&gt;
Cc: Petr Vandrovec &lt;petr@vandrovec.name&gt;
Cc: xfs@oss.sgi.com
Cc: linux-btrfs@vger.kernel.org
Cc: linux-cifs@vger.kernel.org
Cc: samba-technical@lists.samba.org
Cc: codalist@coda.cs.cmu.edu
Cc: linux-ext4@vger.kernel.org
Cc: linux-f2fs-devel@lists.sourceforge.net
Cc: fuse-devel@lists.sourceforge.net
Cc: cluster-devel@redhat.com
Cc: linux-mtd@lists.infradead.org
Cc: jfs-discussion@lists.sourceforge.net
Cc: linux-nfs@vger.kernel.org
Cc: linux-nilfs@vger.kernel.org
Cc: linux-ntfs-dev@lists.sourceforge.net
Cc: ocfs2-devel@oss.oracle.com
Cc: reiserfs-devel@vger.kernel.org
</pre>
</div>
</content>
</entry>
<entry>
<title>sysv: Add forgotten superblock lock init for v7 fs</title>
<updated>2013-09-30T02:02:02+00:00</updated>
<author>
<name>Lubomir Rintel</name>
<email>lkundrak@v3.sk</email>
</author>
<published>2013-09-18T10:39:16+00:00</published>
<link rel='alternate' type='text/html' href='https://git.exis.tech/linux.git/commit/?id=49475555848d396a0c78fb2f8ecceb3f3f263ef1'/>
<id>49475555848d396a0c78fb2f8ecceb3f3f263ef1</id>
<content type='text'>
Superblock lock was replaced with (un)lock_super() removal, but left
uninitialized for Seventh Edition UNIX filesystem in the following commit (3.7):
c07cb01 sysv: drop lock/unlock super

Signed-off-by: Lubomir Rintel &lt;lkundrak@v3.sk&gt;
Signed-off-by: Christoph Hellwig &lt;hch@lst.de&gt;
Signed-off-by: Al Viro &lt;viro@zeniv.linux.org.uk&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Superblock lock was replaced with (un)lock_super() removal, but left
uninitialized for Seventh Edition UNIX filesystem in the following commit (3.7):
c07cb01 sysv: drop lock/unlock super

Signed-off-by: Lubomir Rintel &lt;lkundrak@v3.sk&gt;
Signed-off-by: Christoph Hellwig &lt;hch@lst.de&gt;
Signed-off-by: Al Viro &lt;viro@zeniv.linux.org.uk&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>truncate: drop 'oldsize' truncate_pagecache() parameter</title>
<updated>2013-09-12T22:38:02+00:00</updated>
<author>
<name>Kirill A. Shutemov</name>
<email>kirill.shutemov@linux.intel.com</email>
</author>
<published>2013-09-12T22:13:56+00:00</published>
<link rel='alternate' type='text/html' href='https://git.exis.tech/linux.git/commit/?id=7caef26767c1727d7abfbbbfbe8b2bb473430d48'/>
<id>7caef26767c1727d7abfbbbfbe8b2bb473430d48</id>
<content type='text'>
truncate_pagecache() doesn't care about old size since commit
cedabed49b39 ("vfs: Fix vmtruncate() regression").  Let's drop it.

Signed-off-by: Kirill A. Shutemov &lt;kirill.shutemov@linux.intel.com&gt;
Cc: OGAWA Hirofumi &lt;hirofumi@mail.parknet.co.jp&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
truncate_pagecache() doesn't care about old size since commit
cedabed49b39 ("vfs: Fix vmtruncate() regression").  Let's drop it.

Signed-off-by: Kirill A. Shutemov &lt;kirill.shutemov@linux.intel.com&gt;
Cc: OGAWA Hirofumi &lt;hirofumi@mail.parknet.co.jp&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Don't pass inode to -&gt;d_hash() and -&gt;d_compare()</title>
<updated>2013-06-29T08:57:36+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2013-05-21T22:22:44+00:00</published>
<link rel='alternate' type='text/html' href='https://git.exis.tech/linux.git/commit/?id=da53be12bbb4fabbe2e9f6f908de0cf478b5161d'/>
<id>da53be12bbb4fabbe2e9f6f908de0cf478b5161d</id>
<content type='text'>
Instances either don't look at it at all (the majority of cases) or
only want it to find the superblock (which can be had as dentry-&gt;d_sb).
A few cases that want more are actually safe with dentry-&gt;d_inode -
the only precaution needed is the check that it hadn't been replaced with
NULL by rmdir() or by overwriting rename(), which case should be simply
treated as cache miss.

Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Signed-off-by: Al Viro &lt;viro@zeniv.linux.org.uk&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Instances either don't look at it at all (the majority of cases) or
only want it to find the superblock (which can be had as dentry-&gt;d_sb).
A few cases that want more are actually safe with dentry-&gt;d_inode -
the only precaution needed is the check that it hadn't been replaced with
NULL by rmdir() or by overwriting rename(), which case should be simply
treated as cache miss.

Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Signed-off-by: Al Viro &lt;viro@zeniv.linux.org.uk&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>[readdir] simple local unixlike: switch to -&gt;iterate()</title>
<updated>2013-06-29T08:46:47+00:00</updated>
<author>
<name>Al Viro</name>
<email>viro@zeniv.linux.org.uk</email>
</author>
<published>2013-05-15T22:51:49+00:00</published>
<link rel='alternate' type='text/html' href='https://git.exis.tech/linux.git/commit/?id=80886298c07234331458e963b5f9f57c68edd700'/>
<id>80886298c07234331458e963b5f9f57c68edd700</id>
<content type='text'>
ext2, ufs, minix, sysv

Signed-off-by: Al Viro &lt;viro@zeniv.linux.org.uk&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
ext2, ufs, minix, sysv

Signed-off-by: Al Viro &lt;viro@zeniv.linux.org.uk&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>fs: Readd the fs module aliases.</title>
<updated>2013-03-13T01:55:21+00:00</updated>
<author>
<name>Eric W. Biederman</name>
<email>ebiederm@xmission.com</email>
</author>
<published>2013-03-13T01:27:41+00:00</published>
<link rel='alternate' type='text/html' href='https://git.exis.tech/linux.git/commit/?id=fa7614ddd6c2368b8cd54cc67ab4b767af0a2a50'/>
<id>fa7614ddd6c2368b8cd54cc67ab4b767af0a2a50</id>
<content type='text'>
I had assumed that the only use of module aliases for filesystems
prior to "fs: Limit sys_mount to only request filesystem modules."
was in request_module.  It turns out I was wrong.  At least mkinitcpio
in Arch linux uses these aliases.

So readd the preexising aliases, to keep from breaking userspace.

Userspace eventually will have to follow and use the same aliases the
kernel does.  So at some point we may be delete these aliases without
problems.  However that day is not today.

Signed-off-by: "Eric W. Biederman" &lt;ebiederm@xmission.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
I had assumed that the only use of module aliases for filesystems
prior to "fs: Limit sys_mount to only request filesystem modules."
was in request_module.  It turns out I was wrong.  At least mkinitcpio
in Arch linux uses these aliases.

So readd the preexising aliases, to keep from breaking userspace.

Userspace eventually will have to follow and use the same aliases the
kernel does.  So at some point we may be delete these aliases without
problems.  However that day is not today.

Signed-off-by: "Eric W. Biederman" &lt;ebiederm@xmission.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>fs: Limit sys_mount to only request filesystem modules.</title>
<updated>2013-03-04T03:36:31+00:00</updated>
<author>
<name>Eric W. Biederman</name>
<email>ebiederm@xmission.com</email>
</author>
<published>2013-03-03T03:39:14+00:00</published>
<link rel='alternate' type='text/html' href='https://git.exis.tech/linux.git/commit/?id=7f78e0351394052e1a6293e175825eb5c7869507'/>
<id>7f78e0351394052e1a6293e175825eb5c7869507</id>
<content type='text'>
Modify the request_module to prefix the file system type with "fs-"
and add aliases to all of the filesystems that can be built as modules
to match.

A common practice is to build all of the kernel code and leave code
that is not commonly needed as modules, with the result that many
users are exposed to any bug anywhere in the kernel.

Looking for filesystems with a fs- prefix limits the pool of possible
modules that can be loaded by mount to just filesystems trivially
making things safer with no real cost.

Using aliases means user space can control the policy of which
filesystem modules are auto-loaded by editing /etc/modprobe.d/*.conf
with blacklist and alias directives.  Allowing simple, safe,
well understood work-arounds to known problematic software.

This also addresses a rare but unfortunate problem where the filesystem
name is not the same as it's module name and module auto-loading
would not work.  While writing this patch I saw a handful of such
cases.  The most significant being autofs that lives in the module
autofs4.

This is relevant to user namespaces because we can reach the request
module in get_fs_type() without having any special permissions, and
people get uncomfortable when a user specified string (in this case
the filesystem type) goes all of the way to request_module.

After having looked at this issue I don't think there is any
particular reason to perform any filtering or permission checks beyond
making it clear in the module request that we want a filesystem
module.  The common pattern in the kernel is to call request_module()
without regards to the users permissions.  In general all a filesystem
module does once loaded is call register_filesystem() and go to sleep.
Which means there is not much attack surface exposed by loading a
filesytem module unless the filesystem is mounted.  In a user
namespace filesystems are not mounted unless .fs_flags = FS_USERNS_MOUNT,
which most filesystems do not set today.

Acked-by: Serge Hallyn &lt;serge.hallyn@canonical.com&gt;
Acked-by: Kees Cook &lt;keescook@chromium.org&gt;
Reported-by: Kees Cook &lt;keescook@google.com&gt;
Signed-off-by: "Eric W. Biederman" &lt;ebiederm@xmission.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Modify the request_module to prefix the file system type with "fs-"
and add aliases to all of the filesystems that can be built as modules
to match.

A common practice is to build all of the kernel code and leave code
that is not commonly needed as modules, with the result that many
users are exposed to any bug anywhere in the kernel.

Looking for filesystems with a fs- prefix limits the pool of possible
modules that can be loaded by mount to just filesystems trivially
making things safer with no real cost.

Using aliases means user space can control the policy of which
filesystem modules are auto-loaded by editing /etc/modprobe.d/*.conf
with blacklist and alias directives.  Allowing simple, safe,
well understood work-arounds to known problematic software.

This also addresses a rare but unfortunate problem where the filesystem
name is not the same as it's module name and module auto-loading
would not work.  While writing this patch I saw a handful of such
cases.  The most significant being autofs that lives in the module
autofs4.

This is relevant to user namespaces because we can reach the request
module in get_fs_type() without having any special permissions, and
people get uncomfortable when a user specified string (in this case
the filesystem type) goes all of the way to request_module.

After having looked at this issue I don't think there is any
particular reason to perform any filtering or permission checks beyond
making it clear in the module request that we want a filesystem
module.  The common pattern in the kernel is to call request_module()
without regards to the users permissions.  In general all a filesystem
module does once loaded is call register_filesystem() and go to sleep.
Which means there is not much attack surface exposed by loading a
filesytem module unless the filesystem is mounted.  In a user
namespace filesystems are not mounted unless .fs_flags = FS_USERNS_MOUNT,
which most filesystems do not set today.

Acked-by: Serge Hallyn &lt;serge.hallyn@canonical.com&gt;
Acked-by: Kees Cook &lt;keescook@chromium.org&gt;
Reported-by: Kees Cook &lt;keescook@google.com&gt;
Signed-off-by: "Eric W. Biederman" &lt;ebiederm@xmission.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>new helper: file_inode(file)</title>
<updated>2013-02-23T04:31:31+00:00</updated>
<author>
<name>Al Viro</name>
<email>viro@zeniv.linux.org.uk</email>
</author>
<published>2013-01-23T22:07:38+00:00</published>
<link rel='alternate' type='text/html' href='https://git.exis.tech/linux.git/commit/?id=496ad9aa8ef448058e36ca7a787c61f2e63f0f54'/>
<id>496ad9aa8ef448058e36ca7a787c61f2e63f0f54</id>
<content type='text'>
Signed-off-by: Al Viro &lt;viro@zeniv.linux.org.uk&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Signed-off-by: Al Viro &lt;viro@zeniv.linux.org.uk&gt;
</pre>
</div>
</content>
</entry>
</feed>
