linux-toradex.git/fs/jffs2/super.c, branch v3.14-rc8 Linux kernel for Apalis and Colibri modules fs: Limit sys_mount to only request filesystem modules. 2013-03-04T03:36:31+00:00 Eric W. Biederman ebiederm@xmission.com 2013-03-03T03:39:14+00:00 7f78e0351394052e1a6293e175825eb5c7869507 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 <serge.hallyn@canonical.com> Acked-by: Kees Cook <keescook@chromium.org> Reported-by: Kees Cook <keescook@google.com> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> 
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 <serge.hallyn@canonical.com>
Acked-by: Kees Cook <keescook@chromium.org>
Reported-by: Kees Cook <keescook@google.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Merge tag 'disintegrate-mtd-20121009' of git://git.infradead.org/users/dhowells/linux-headers 2012-10-09T14:04:25+00:00 David Woodhouse David.Woodhouse@intel.com 2012-10-09T14:03:21+00:00 ffe315012510165ce82e4dd4767f0a5dba9edbf7 UAPI Disintegration 2012-10-09 Conflicts: MAINTAINERS arch/arm/configs/bcmring_defconfig arch/arm/mach-imx/clk-imx51-imx53.c drivers/mtd/nand/Kconfig drivers/mtd/nand/bcm_umi_nand.c drivers/mtd/nand/nand_bcm_umi.h drivers/mtd/nand/orion_nand.c 
UAPI Disintegration 2012-10-09

Conflicts:
	MAINTAINERS
	arch/arm/configs/bcmring_defconfig
	arch/arm/mach-imx/clk-imx51-imx53.c
	drivers/mtd/nand/Kconfig
	drivers/mtd/nand/bcm_umi_nand.c
	drivers/mtd/nand/nand_bcm_umi.h
	drivers/mtd/nand/orion_nand.c
fs: push rcu_barrier() from deactivate_locked_super() to filesystems 2012-10-03T01:35:55+00:00 Kirill A. Shutemov kirill.shutemov@linux.intel.com 2012-09-26T01:33:07+00:00 8c0a85377048b64c880e76ec7368904fe46d0b94 There's no reason to call rcu_barrier() on every deactivate_locked_super(). We only need to make sure that all delayed rcu free inodes are flushed before we destroy related cache. Removing rcu_barrier() from deactivate_locked_super() affects some fast paths. E.g. on my machine exit_group() of a last process in IPC namespace takes 0.07538s. rcu_barrier() takes 0.05188s of that time. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> 
There's no reason to call rcu_barrier() on every
deactivate_locked_super().  We only need to make sure that all delayed rcu
free inodes are flushed before we destroy related cache.

Removing rcu_barrier() from deactivate_locked_super() affects some fast
paths.  E.g.  on my machine exit_group() of a last process in IPC
namespace takes 0.07538s.  rcu_barrier() takes 0.05188s of that time.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
JFFS2: fix unmount regression 2012-09-29T13:58:42+00:00 Artem Bityutskiy artem.bityutskiy@linux.intel.com 2012-08-23T07:10:07+00:00 a445f784ae5558a3da680aa6b39ed53c95a551c1 This patch fixes regression introduced by "8bdc81c jffs2: get rid of jffs2_sync_super". We submit a delayed work in order to make sure the write-buffer is synchronized at some point. But we do not flush it when we unmount, which causes an oops when we unmount the file-system and then the delayed work is executed. This patch fixes the issue by adding a "cancel_delayed_work_sync()" infocation in the '->sync_fs()' handler. This will make sure the delayed work is canceled on sync, unmount and re-mount. And because VFS always callse 'sync_fs()' before unmounting or remounting, this fixes the issue. Reported-by: Ludovic Desroches <ludovic.desroches@atmel.com> Cc: stable@vger.kernel.org [3.5+] Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Tested-by: Ludovic Desroches <ludovic.desroches@atmel.com> Signed-off-by: David Woodhouse <David.Woodhouse@intel.com> 
This patch fixes regression introduced by
"8bdc81c jffs2: get rid of jffs2_sync_super". We submit a delayed work in order
to make sure the write-buffer is synchronized at some point. But we do not
flush it when we unmount, which causes an oops when we unmount the file-system
and then the delayed work is executed.

This patch fixes the issue by adding a "cancel_delayed_work_sync()" infocation
in the '->sync_fs()' handler. This will make sure the delayed work is canceled
on sync, unmount and re-mount. And because VFS always callse 'sync_fs()' before
unmounting or remounting, this fixes the issue.

Reported-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Cc: stable@vger.kernel.org [3.5+]
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Tested-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
jffs2: get rid of jffs2_sync_super 2012-05-14T04:24:23+00:00 Artem Bityutskiy artem.bityutskiy@linux.intel.com 2012-05-07T16:02:46+00:00 208b14e507c00ff7f108e1a388dd3d8cc805a443 Currently JFFS2 file-system maps the VFS "superblock" abstraction to the write-buffer. Namely, it uses VFS services to synchronize the write-buffer periodically. The whole "superblock write-out" VFS infrastructure is served by the 'sync_supers()' kernel thread, which wakes up every 5 (by default) seconds and writes out all dirty superblock using the '->write_super()' call-back. But the problem with this thread is that it wastes power by waking up the system every 5 seconds no matter what. So we want to kill it completely and thus, we need to make file-systems to stop using the '->write_super' VFS service, and then remove it together with the kernel thread. This patch switches the JFFS2 write-buffer management from '->write_super()'/'->s_dirt' to a delayed work. Instead of setting the 's_dirt' flag we just schedule a delayed work for synchronizing the write-buffer. Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Signed-off-by: David Woodhouse <David.Woodhouse@intel.com> 
Currently JFFS2 file-system maps the VFS "superblock" abstraction to the
write-buffer. Namely, it uses VFS services to synchronize the write-buffer
periodically.

The whole "superblock write-out" VFS infrastructure is served by the
'sync_supers()' kernel thread, which wakes up every 5 (by default) seconds and
writes out all dirty superblock using the '->write_super()' call-back. But the
problem with this thread is that it wastes power by waking up the system every
5 seconds no matter what. So we want to kill it completely and thus, we need to
make file-systems to stop using the '->write_super' VFS service, and then
remove it together with the kernel thread.

This patch switches the JFFS2 write-buffer management from
'->write_super()'/'->s_dirt' to a delayed work. Instead of setting the 's_dirt'
flag we just schedule a delayed work for synchronizing the write-buffer.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
jffs2: remove unnecessary GC pass on sync 2012-05-14T04:23:12+00:00 Artem Bityutskiy artem.bityutskiy@linux.intel.com 2012-05-07T15:51:54+00:00 e832579fd100eb4f9658bdfefd61caf86a6cbff1 We do not need to call 'jffs2_write_super()' on sync. This function causes a GC pass to make sure the current contents is pushed out with the data which we already have on the media. But this is not needed on unmount and only slows sync down unnecessarily. It is enough to just sync the write-buffer. This call was added by one of the generic VFS rework patch-sets, see d579ed00aa96a7f7486978540a0d7cecaff742ae. Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Signed-off-by: David Woodhouse <David.Woodhouse@intel.com> 
We do not need to call 'jffs2_write_super()' on sync. This function
causes a GC pass to make sure the current contents is pushed out with
the data which we already have on the media.

But this is not needed on unmount and only slows sync down unnecessarily.
It is enough to just sync the write-buffer.

This call was added by one of the generic VFS rework patch-sets,
see d579ed00aa96a7f7486978540a0d7cecaff742ae.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
jffs2: remove unnecessary GC pass on umount 2012-05-14T04:23:01+00:00 Artem Bityutskiy artem.bityutskiy@linux.intel.com 2012-05-07T15:45:39+00:00 c3c4a36979c8b68cc35643497e83c7383cd07955 We do not need to call 'jffs2_write_super()' on unmount. This function causes a GC pass to make sure the current contents is pushed out with the data which we already have on the media. But this is not needed on unmount and only slows unmount down unnecessarily. It is enough to just sync the write-buffer. This call was added by one of the generic VFS rework patch-sets, see 8c85e125124a473d6f3e9bb187b0b84207f81d91. Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Signed-off-by: David Woodhouse <David.Woodhouse@intel.com> 
We do not need to call 'jffs2_write_super()' on unmount. This function
causes a GC pass to make sure the current contents is pushed out with
the data which we already have on the media.

But this is not needed on unmount and only slows unmount down unnecessarily.
It is enough to just sync the write-buffer.

This call was added by one of the generic VFS rework patch-sets,
see 8c85e125124a473d6f3e9bb187b0b84207f81d91.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
jffs2: remove lock_super 2012-05-14T04:22:38+00:00 Artem Bityutskiy artem.bityutskiy@linux.intel.com 2012-05-07T15:25:00+00:00 f4d0b3557582808d5ce9f868e9dfd98f0e769e82 We do not need 'lock_super()'/'unlock_super()' in JFFS2 - kill them. Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Signed-off-by: David Woodhouse <David.Woodhouse@intel.com> 
We do not need 'lock_super()'/'unlock_super()' in JFFS2 - kill them.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
JFFS2: Add parameter to reserve disk space for root 2012-05-14T03:51:29+00:00 Daniel Drake dsd@laptop.org 2012-04-10T21:22:35+00:00 8da8ba2ea6ad52ea8558384f38586b0c1a516e9d Add a new rp_size= parameter which creates a "reserved pool" of disk space which can only be used by root. Other users are not permitted to write to disk when the available space is less than the pool size. Based on original code by Artem Bityutskiy in https://dev.laptop.org/ticket/5317 [dwmw2: use capable(CAP_SYS_RESOURCE) not uid/gid check, fix debug prints] Signed-off-by: Daniel Drake <dsd@laptop.org> Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@linux.intel.com> Signed-off-by: David Woodhouse <David.Woodhouse@intel.com> 
Add a new rp_size= parameter which creates a "reserved pool" of disk
space which can only be used by root. Other users are not permitted
to write to disk when the available space is less than the pool size.

Based on original code by Artem Bityutskiy in
https://dev.laptop.org/ticket/5317

[dwmw2: use capable(CAP_SYS_RESOURCE) not uid/gid check, fix debug prints]
Signed-off-by: Daniel Drake <dsd@laptop.org>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
jffs2: Use pr_fmt and remove jffs: from formats 2012-03-26T23:40:19+00:00 Joe Perches joe@perches.com 2012-02-15T23:56:45+00:00 5a528957e7c74f1fed73fe20424b7a3421658877 Use pr_fmt to prefix KBUILD_MODNAME to appropriate logging messages. Remove now unnecessary internal prefixes from formats. Signed-off-by: Joe Perches <joe@perches.com> Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Signed-off-by: David Woodhouse <David.Woodhouse@intel.com> 
Use pr_fmt to prefix KBUILD_MODNAME to appropriate logging messages.

Remove now unnecessary internal prefixes from formats.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>