kernel.git/fs/ufs/super.c, branch linux-3.14.y

fs: Limit sys_mount to only request filesystem modules.

2013-03-04T03:36:31Z

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 Acked-by: Kees Cook Reported-by: Kees Cook Signed-off-by: "Eric W. Biederman"

ufs: drop lock/unlock super

2012-10-10T03:33:39Z

Removed lock/unlock super. Added a new private s_lock mutex. Signed-off-by: Marco Stornelli Signed-off-by: Al Viro

fs: push rcu_barrier() from deactivate_locked_super() to filesystems

2012-10-03T01:35:55Z

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 Cc: Al Viro Signed-off-by: Andrew Morton Signed-off-by: Al Viro

fs/ufs: get rid of write_super

2012-07-22T19:58:16Z

This patch makes UFS stop using the VFS '->write_super()' method along with the 's_dirt' superblock flag, because they are on their way out. The way we implement this is that we schedule a delay job instead relying on 's_dirt' and '->write_super()'. 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 superblocks 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, even if there are no diry superblocks, or there are no client file-systems which would need this (e.g., btrfs does not use '->write_super()'). 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. Tested using fsstress from the LTP project. Signed-off-by: Artem Bityutskiy Signed-off-by: Al Viro

fs/ufs: re-arrange the code a bit

2012-07-22T19:58:14Z

This patch does not do any functional changes. It only moves 3 functions in fs/ufs/super.c a little bit up in order to prepare for further changes where I'll need this new arrangement to avoid forward declarations. Signed-off-by: Artem Bityutskiy Signed-off-by: Al Viro

fs/ufs: remove extra superblock write on unmount

2012-07-22T19:58:14Z

UFS calls 'ufs_write_super()' from 'ufs_put_super()' in order to write the superblocks to the media. However, it is not needed because VFS calls '->sync_fs()' before calling '->put_super()' - so by the time we are in 'ufs_write_super()', the superblocks are already synchronized. Signed-off-by: Artem Bityutskiy Signed-off-by: Al Viro

vfs: make it possible to access the dentry hash/len as one 64-bit entry

2012-05-11T02:54:35Z

This allows comparing hash and len in one operation on 64-bit architectures. Right now only __d_lookup_rcu() takes advantage of this, since that is the case we care most about. The use of anonymous struct/unions hides the alternate 64-bit approach from most users, the exception being a few cases where we initialize a 'struct qstr' with a static initializer. This makes the problematic cases use a new QSTR_INIT() helper function for that (but initializing just the name pointer with a "{ .name = xyzzy }" initializer remains valid, as does just copying another qstr structure). Signed-off-by: Linus Torvalds

Remove all #inclusions of asm/system.h

2012-03-28T17:30:03Z

Remove all #inclusions of asm/system.h preparatory to splitting and killing it. Performed with the following command: perl -p -i -e 's!^#\s*include\s*.*\n!!' `grep -Irl '^#\s*include\s*' *` Signed-off-by: David Howells

switch open-coded instances of d_make_root() to new helper

2012-03-21T01:29:35Z

Signed-off-by: Al Viro

vfs: check i_nlink limits in vfs_{mkdir,rename_dir,link}

2012-03-21T01:29:32Z

New field of struct super_block - ->s_max_links. Maximal allowed value of ->i_nlink or 0; in the latter case all checks still need to be done in ->link/->mkdir/->rename instances. Note that this limit applies both to directoris and to non-directories. Signed-off-by: Al Viro