summaryrefslogtreecommitdiffstats
path: root/fs/configfs/dir.c
AgeCommit message (Collapse)AuthorFilesLines
2013-11-21configfs: fix race between dentry put and lookupJunxiao Bi1-2/+14
A race window in configfs, it starts from one dentry is UNHASHED and end before configfs_d_iput is called. In this window, if a lookup happen, since the original dentry was UNHASHED, so a new dentry will be allocated, and then in configfs_attach_attr(), sd->s_dentry will be updated to the new dentry. Then in configfs_d_iput(), BUG_ON(sd->s_dentry != dentry) will be triggered and system panic. sys_open: sys_close: ... fput dput dentry_kill __d_drop <--- dentry unhashed here, but sd->dentry still point to this dentry. lookup_real configfs_lookup configfs_attach_attr---> update sd->s_dentry to new allocated dentry here. d_kill configfs_d_iput <--- BUG_ON(sd->s_dentry != dentry) triggered here. To fix it, change configfs_d_iput to not update sd->s_dentry if sd->s_count > 2, that means there are another dentry is using the sd beside the one that is going to be put. Use configfs_dirent_lock in configfs_attach_attr to sync with configfs_d_iput. With the following steps, you can reproduce the bug. 1. enable ocfs2, this will mount configfs at /sys/kernel/config and fill configure in it. 2. run the following script. while [ 1 ]; do cat /sys/kernel/config/cluster/$your_cluster_name/idle_timeout_ms > /dev/null; done & while [ 1 ]; do cat /sys/kernel/config/cluster/$your_cluster_name/idle_timeout_ms > /dev/null; done & Signed-off-by: Junxiao Bi <junxiao.bi@oracle.com> Cc: Joel Becker <jlbec@evilplan.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-11-15consolidate simple ->d_delete() instancesAl Viro1-11/+1
Rename simple_delete_dentry() to always_delete_dentry() and export it. Export simple_dentry_operations, while we are at it, and get rid of their duplicates Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-07-14Merge branch 'for-linus' of ↵Linus Torvalds1-11/+2
git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs Pull more vfs stuff from Al Viro: "O_TMPFILE ABI changes, Oleg's fput() series, misc cleanups, including making simple_lookup() usable for filesystems with non-NULL s_d_op, which allows us to get rid of quite a bit of ugliness" * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: sunrpc: now we can just set ->s_d_op cgroup: we can use simple_lookup() now efivarfs: we can use simple_lookup() now make simple_lookup() usable for filesystems that set ->s_d_op configfs: don't open-code d_alloc_name() __rpc_lookup_create_exclusive: pass string instead of qstr rpc_create_*_dir: don't bother with qstr llist: llist_add() can use llist_add_batch() llist: fix/simplify llist_add() and llist_add_batch() fput: turn "list_head delayed_fput_list" into llist_head fs/file_table.c:fput(): add comment Safer ABI for O_TMPFILE
2013-07-14configfs: don't open-code d_alloc_name()Al Viro1-11/+2
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-07-09Merge branch 'for-linus' of ↵Linus Torvalds1-1/+1
git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs Pull third set of VFS updates from Al Viro: "Misc stuff all over the place. There will be one more pile in a couple of days" This is an "evil merge" that also uses the new d_count helper in fs/configfs/dir.c, missed by commit 84d08fa888e7 ("helper for reading ->d_count") * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: ncpfs: fix error return code in ncp_parse_options() locks: move file_lock_list to a set of percpu hlist_heads and convert file_lock_lock to an lglock seq_file: add seq_list_*_percpu helpers f2fs: fix readdir incorrectness mode_t whack-a-mole... lustre: kill the pointless wrapper helper for reading ->d_count
2013-06-29[readdir] convert configfsAl Viro1-70/+52
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-02-26Merge branch 'for-linus' of ↵Linus Torvalds1-1/+1
git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs Pull vfs pile (part one) from Al Viro: "Assorted stuff - cleaning namei.c up a bit, fixing ->d_name/->d_parent locking violations, etc. The most visible changes here are death of FS_REVAL_DOT (replaced with "has ->d_weak_revalidate()") and a new helper getting from struct file to inode. Some bits of preparation to xattr method interface changes. Misc patches by various people sent this cycle *and* ocfs2 fixes from several cycles ago that should've been upstream right then. PS: the next vfs pile will be xattr stuff." * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (46 commits) saner proc_get_inode() calling conventions proc: avoid extra pde_put() in proc_fill_super() fs: change return values from -EACCES to -EPERM fs/exec.c: make bprm_mm_init() static ocfs2/dlm: use GFP_ATOMIC inside a spin_lock ocfs2: fix possible use-after-free with AIO ocfs2: Fix oops in ocfs2_fast_symlink_readpage() code path get_empty_filp()/alloc_file() leave both ->f_pos and ->f_version zero target: writev() on single-element vector is pointless export kernel_write(), convert open-coded instances fs: encode_fh: return FILEID_INVALID if invalid fid_type kill f_vfsmnt vfs: kill FS_REVAL_DOT by adding a d_weak_revalidate dentry op nfsd: handle vfs_getattr errors in acl protocol switch vfs_getattr() to struct path default SET_PERSONALITY() in linux/elf.h ceph: prepopulate inodes only when request is aborted d_hash_and_lookup(): export, switch open-coded instances 9p: switch v9fs_set_create_acl() to inode+fid, do it before d_instantiate() 9p: split dropping the acls from v9fs_set_create_acl() ...
2013-02-22new helper: file_inode(file)Al Viro1-1/+1
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2013-02-21configfs: move the dereference below the NULL testWei Yongjun1-2/+3
The dereference should be moved below the NULL test. spatch with a semantic match is used to found this. (http://coccinelle.lip6.fr/) Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn> Cc: Joel Becker <jlbec@evilplan.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-12-17lseek: the "whence" argument is called "whence"Andrew Morton1-2/+2
But the kernel decided to call it "origin" instead. Fix most of the sites. Acked-by: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-07-14stop passing nameidata to ->lookup()Al Viro1-1/+1
Just the flags; only NFS cares even about that, but there are legitimate uses for such argument. And getting rid of that completely would require splitting ->lookup() into a couple of methods (at least), so let's leave that alone for now... Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-03-20make configfs_pin_fs() return root dentry on successAl Viro1-8/+6
... and make configfs_mnt static Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-03-20configfs: configfs_create_dir() has parent dentry in dentry->d_parentAl Viro1-15/+5
no need to play sick games with parent item, internal mount, etc. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-03-20configfs: kill configfs_sbAl Viro1-12/+17
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-03-20configfs: don't bother with checks for mkdir/rmdir/unlink/symlink in rootAl Viro1-8/+5
just give root directory separate inode_operations without all those methods... Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-01-03switch vfs_mkdir() and ->mkdir() to umode_tAl Viro1-1/+1
vfs_mkdir() gets int, but immediately drops everything that might not fit into umode_t and that's the only caller of ->mkdir()... Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-01-03vfs: live vfsmounts never have NULL ->mnt_sbAl Viro1-1/+1
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-01-03vfs: for usbfs, etc. internal vfsmounts ->mnt_sb->s_root == ->mnt_rootAl Viro1-1/+1
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-05-28configfs: remove unnecessary dentry_unhash on rmdir, dir renameSage Weil1-2/+0
configfs does not have problems with references to unlinked directories. CC: Joel Becker <jlbec@evilplan.org> Signed-off-by: Sage Weil <sage@newdream.net> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-05-26Merge branch 'for-linus' of ↵Linus Torvalds1-0/+2
git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6 * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6: (25 commits) cifs: remove unnecessary dentry_unhash on rmdir/rename_dir ocfs2: remove unnecessary dentry_unhash on rmdir/rename_dir exofs: remove unnecessary dentry_unhash on rmdir/rename_dir nfs: remove unnecessary dentry_unhash on rmdir/rename_dir ext2: remove unnecessary dentry_unhash on rmdir/rename_dir ext3: remove unnecessary dentry_unhash on rmdir/rename_dir ext4: remove unnecessary dentry_unhash on rmdir/rename_dir btrfs: remove unnecessary dentry_unhash in rmdir/rename_dir ceph: remove unnecessary dentry_unhash calls vfs: clean up vfs_rename_other vfs: clean up vfs_rename_dir vfs: clean up vfs_rmdir vfs: fix vfs_rename_dir for FS_RENAME_DOES_D_MOVE filesystems libfs: drop unneeded dentry_unhash vfs: update dentry_unhash() comment vfs: push dentry_unhash on rename_dir into file systems vfs: push dentry_unhash on rmdir into file systems vfs: remove dget() from dentry_unhash() vfs: dentry_unhash immediately prior to rmdir vfs: Block mmapped writes while the fs is frozen ...
2011-05-26vfs: push dentry_unhash on rmdir into file systemsSage Weil1-0/+2
Only a few file systems need this. Start by pushing it down into each fs rmdir method (except gfs2 and xfs) so it can be dealt with on a per-fs basis. This does not change behavior for any in-tree file systems. Acked-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Sage Weil <sage@newdream.net> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-05-18configfs: Fix race between configfs_readdir() and configfs_d_iput()Joel Becker1-5/+28
configfs_readdir() will use the existing inode numbers of inodes in the dcache, but it makes them up for attribute files that aren't currently instantiated. There is a race where a closing attribute file can be tearing down at the same time as configfs_readdir() is trying to get its inode number. We want to get the inode number of open attribute files, because they should match while instantiated. We can't lock down the transition where dentry->d_inode is set to NULL, so we just check for NULL there. We can, however, ensure that an inode we find isn't iput() in configfs_d_iput() until after we've accessed it. Signed-off-by: Joel Becker <jlbec@evilplan.org>
2011-05-18configfs: Don't try to d_delete() negative dentries.Joel Becker1-2/+4
When configfs is faking mkdir() on its subsystem or default group objects, it starts by adding a negative dentry. It then tries to instantiate the group. If that should fail, it must clean up after itself. I was using d_delete() here, but configfs_attach_group() promises to return an empty dentry on error. d_delete() explodes with the entry dentry. Let's try d_drop() instead. The unhashing is what we want for our dentry. Signed-off-by: Joel Becker <jlbec@evilplan.org>
2011-03-31Fix common misspellingsLucas De Marchi1-1/+1
Fixes generated by 'codespell' and manually reviewed. Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
2011-01-12switch configfsAl Viro1-5/+1
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-01-07fs: dcache reduce branches in lookup pathNick Piggin1-4/+4
Reduce some branches and memory accesses in dcache lookup by adding dentry flags to indicate common d_ops are set, rather than having to check them. This saves a pointer memory access (dentry->d_op) in common path lookup situations, and saves another pointer load and branch in cases where we have d_op but not the particular operation. Patched with: git grep -E '[.>]([[:space:]])*d_op([[:space:]])*=' | xargs sed -e 's/\([^\t ]*\)->d_op = \(.*\);/d_set_d_op(\1, \2);/' -e 's/\([^\t ]*\)\.d_op = \(.*\);/d_set_d_op(\&\1, \2);/' -i Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07fs: dcache scale dentry refcountNick Piggin1-2/+1
Make d_count non-atomic and protect it with d_lock. This allows us to ensure a 0 refcount dentry remains 0 without dcache_lock. It is also fairly natural when we start protecting many other dentry members with d_lock. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07fs: change d_delete semanticsNick Piggin1-1/+1
Change d_delete from a dentry deletion notification to a dentry caching advise, more like ->drop_inode. Require it to be constant and idempotent, and not take d_lock. This is how all existing filesystems use the callback anyway. This makes fine grained dentry locking of dput and dentry lru scanning much simpler. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07config fs: avoid switching ->d_op on live dentryNick Piggin1-8/+9
Switching d_op on a live dentry is racy in general, so avoid it. In this case it is a negative dentry, which is safer, but there are still concurrent ops which may be called on d_op in that case (eg. d_revalidate). So in general a filesystem may not do this. Fix configfs so as not to do this. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2010-05-15Fix the regression created by "set S_DEAD on unlink()..." commitAl Viro1-0/+4
1) i_flags simply doesn't work for mount/unlink race prevention; we may have many links to file and rm on one of those obviously shouldn't prevent bind on top of another later on. To fix it right way we need to mark _dentry_ as unsuitable for mounting upon; new flag (DCACHE_CANT_MOUNT) is protected by d_flags and i_mutex on the inode in question. Set it (with dont_mount(dentry)) in unlink/rmdir/etc., check (with cant_mount(dentry)) in places in namespace.c that used to check for S_DEAD. Setting S_DEAD is still needed in places where we used to set it (for directories getting killed), since we rely on it for readdir/rmdir race prevention. 2) rename()/mount() protection has another bogosity - we unhash the target before we'd checked that it's not a mountpoint. Fixed. 3) ancient bogosity in pivot_root() - we locked i_mutex on the right directory, but checked S_DEAD on the different (and wrong) one. Noticed and fixed. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2009-04-30configfs: Rework configfs_depend_item() locking and make lockdep happyLouis Rilling1-59/+47
configfs_depend_item() recursively locks all inodes mutex from configfs root to the target item, which makes lockdep unhappy. The purpose of this recursive locking is to ensure that the item tree can be safely parsed and that the target item, if found, is not about to leave. This patch reworks configfs_depend_item() locking using configfs_dirent_lock. Since configfs_dirent_lock protects all changes to the configfs_dirent tree, and protects tagging of items to be removed, this lock can be used instead of the inodes mutex lock chain. This needs that the check for dependents be done atomically with CONFIGFS_USET_DROPPING tagging. Now lockdep looks happy with configfs. [ Lifted the setting of s_type into configfs_new_dirent() to satisfy the atomic setting of CONFIGFS_USET_CREATING -- Joel ] Signed-off-by: Louis Rilling <louis.rilling@kerlabs.com> Signed-off-by: Joel Becker <joel.becker@oracle.com>
2009-04-30configfs: Silence lockdep on mkdir() and rmdir()Louis Rilling1-0/+90
When attaching default groups (subdirs) of a new group (in mkdir() or in configfs_register()), configfs recursively takes inode's mutexes along the path from the parent of the new group to the default subdirs. This is needed to ensure that the VFS will not race with operations on these sub-dirs. This is safe for the following reasons: - the VFS allows one to lock first an inode and second one of its children (The lock subclasses for this pattern are respectively I_MUTEX_PARENT and I_MUTEX_CHILD); - from this rule any inode path can be recursively locked in descending order as long as it stays under a single mountpoint and does not follow symlinks. Unfortunately lockdep does not know (yet?) how to handle such recursion. I've tried to use Peter Zijlstra's lock_set_subclass() helper to upgrade i_mutexes from I_MUTEX_CHILD to I_MUTEX_PARENT when we know that we might recursively lock some of their descendant, but this usage does not seem to fit the purpose of lock_set_subclass() because it leads to several i_mutex locked with subclass I_MUTEX_PARENT by the same task. >From inside configfs it is not possible to serialize those recursive locking with a top-level one, because mkdir() and rmdir() are already called with inodes locked by the VFS. So using some mutex_lock_nest_lock() is not an option. I am proposing two solutions: 1) one that wraps recursive mutex_lock()s with lockdep_off()/lockdep_on(). 2) (as suggested earlier by Peter Zijlstra) one that puts the i_mutexes recursively locked in different classes based on their depth from the top-level config_group created. This induces an arbitrary limit (MAX_LOCK_DEPTH - 2 == 46) on the nesting of configfs default groups whenever lockdep is activated but this limit looks reasonably high. Unfortunately, this also isolates VFS operations on configfs default groups from the others and thus lowers the chances to detect locking issues. Nobody likes solution 1), which I can understand. This patch implements solution 2). However lockdep is still not happy with configfs_depend_item(). Next patch reworks the locking of configfs_depend_item() and finally makes lockdep happy. [ Note: This hides a few locking interactions with the VFS from lockdep. That was my big concern, because we like lockdep's protection. However, the current state always dumps a spurious warning. The locking is correct, so I tell people to ignore the warning and that we'll keep our eyes on the locking to make sure it stays correct. With this patch, we eliminate the warning. We do lose some of the lockdep protections, but this only means that we still have to keep our eyes on the locking. We're going to do that anyway. -- Joel ] Signed-off-by: Louis Rilling <louis.rilling@kerlabs.com> Signed-off-by: Joel Becker <joel.becker@oracle.com>
2009-03-27constify dentry_operations: configfsAl Viro1-1/+1
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2009-02-04Revert "configfs: Silence lockdep on mkdir(), rmdir() and ↵Mark Fasheh1-59/+0
configfs_depend_item()" This reverts commit 0e0333429a6280e6eb3c98845e4eed90d5f8078a. I committed this by accident - Joel and Louis are working with the lockdep maintainer to provide a better solution than just turning lockdep off. Signed-off-by: Mark Fasheh <mfasheh@suse.com> Acked-by: <Joel Becker <joel.becker@oracle.com>
2009-02-02configfs: Silence lockdep on mkdir(), rmdir() and configfs_depend_item()Joel Becker1-0/+59
When attaching default groups (subdirs) of a new group (in mkdir() or in configfs_register()), configfs recursively takes inode's mutexes along the path from the parent of the new group to the default subdirs. This is needed to ensure that the VFS will not race with operations on these sub-dirs. This is safe for the following reasons: - the VFS allows one to lock first an inode and second one of its children (The lock subclasses for this pattern are respectively I_MUTEX_PARENT and I_MUTEX_CHILD); - from this rule any inode path can be recursively locked in descending order as long as it stays under a single mountpoint and does not follow symlinks. Unfortunately lockdep does not know (yet?) how to handle such recursion. I've tried to use Peter Zijlstra's lock_set_subclass() helper to upgrade i_mutexes from I_MUTEX_CHILD to I_MUTEX_PARENT when we know that we might recursively lock some of their descendant, but this usage does not seem to fit the purpose of lock_set_subclass() because it leads to several i_mutex locked with subclass I_MUTEX_PARENT by the same task. >From inside configfs it is not possible to serialize those recursive locking with a top-level one, because mkdir() and rmdir() are already called with inodes locked by the VFS. So using some mutex_lock_nest_lock() is not an option. I am proposing two solutions: 1) one that wraps recursive mutex_lock()s with lockdep_off()/lockdep_on(). 2) (as suggested earlier by Peter Zijlstra) one that puts the i_mutexes recursively locked in different classes based on their depth from the top-level config_group created. This induces an arbitrary limit (MAX_LOCK_DEPTH - 2 == 46) on the nesting of configfs default groups whenever lockdep is activated but this limit looks reasonably high. Unfortunately, this alos isolates VFS operations on configfs default groups from the others and thus lowers the chances to detect locking issues. This patch implements solution 1). Solution 2) looks better from lockdep's point of view, but fails with configfs_depend_item(). This needs to rework the locking scheme of configfs_depend_item() by removing the variable lock recursion depth, and I think that it's doable thanks to the configfs_dirent_lock. For now, let's stick to solution 1). Signed-off-by: Louis Rilling <louis.rilling@kerlabs.com> Acked-by: Joel Becker <joel.becker@oracle.com> Signed-off-by: Mark Fasheh <mfasheh@suse.com>
2008-08-22[PATCH] configfs: Consolidate locking around configfs_detach_prep() in ↵Louis Rilling1-10/+7
configfs_rmdir() It appears that configfs_rmdir() can protect configfs_detach_prep() retries with less calls to {spin,mutex}_{lock,unlock}, and a cleaner code. This patch does not change any behavior, except that it removes two useless lock/unlock pairs having nothing inside to protect and providing a useless barrier. Signed-off-by: Louis Rilling <louis.rilling@kerlabs.com> Signed-off-by: Joel Becker <Joel.Becker@oracle.com> Signed-off-by: Mark Fasheh <mfasheh@suse.com>
2008-07-31[PATCH] configfs: Pin configfs subsystems separately from new config_items.Joel Becker1-9/+33
configfs_mkdir() creates a new item by calling its parent's ->make_item/group() functions. Once that object is created, configfs_mkdir() calls try_module_get() on the new item's module. If it succeeds, the module owning the new item cannot be unloaded, and configfs is safe to reference the item. If the item and the subsystem it belongs to are part of the same module, the subsystem is also pinned. This is the common case. However, if the subsystem is made up of multiple modules, this may not pin the subsystem. Thus, it would be possible to unload the toplevel subsystem module while there is still a child item. Thus, we now try_module_get() the subsystem's module. This only really affects children of the toplevel subsystem group. Deeper children already have their parents pinned. Signed-off-by: Joel Becker <joel.becker@oracle.com> Signed-off-by: Mark Fasheh <mfasheh@suse.com>
2008-07-31[PATCH] configfs: Fix open directory making rmdir() failLouis Rilling1-1/+2
When checking for user-created elements under an item to be removed by rmdir(), configfs_detach_prep() counts fake configfs_dirents created by dir_open() as user-created and fails when finding one. It is however perfectly valid to remove a directory that is open. Simply make configfs_detach_prep() skip fake configfs_dirent, like it already does for attributes, and like detach_groups() does. Signed-off-by: Louis Rilling <louis.rilling@kerlabs.com> Signed-off-by: Joel Becker <joel.becker@oracle.com> Signed-off-by: Mark Fasheh <mfasheh@suse.com>
2008-07-31[PATCH] configfs: Lock new directory inodes before removing on cleanup after ↵Louis Rilling1-19/+29
failure Once a new configfs directory is created by configfs_attach_item() or configfs_attach_group(), a failure in the remaining initialization steps leads to removing a directory which inode the VFS may have already accessed. This commit adds the necessary inode locking to safely remove configfs directories while cleaning up after a failure. As an advantage, the locking rules of populate_groups() and detach_groups() become the same: the caller must have the group's inode mutex locked. Signed-off-by: Louis Rilling <louis.rilling@kerlabs.com> Signed-off-by: Joel Becker <joel.becker@oracle.com> Signed-off-by: Mark Fasheh <mfasheh@suse.com>
2008-07-31[PATCH] configfs: Prevent userspace from creating new entries under ↵Louis Rilling1-5/+86
attaching directories process 1: process 2: configfs_mkdir("A") attach_group("A") attach_item("A") d_instantiate("A") populate_groups("A") mutex_lock("A") attach_group("A/B") attach_item("A") d_instantiate("A/B") mkdir("A/B/C") do_path_lookup("A/B/C", LOOKUP_PARENT) ok lookup_create("A/B/C") mutex_lock("A/B") ok configfs_mkdir("A/B/C") ok attach_group("A/C") attach_item("A/C") d_instantiate("A/C") populate_groups("A/C") mutex_lock("A/C") attach_group("A/C/D") attach_item("A/C/D") failure mutex_unlock("A/C") detach_groups("A/C") nothing to do mkdir("A/C/E") do_path_lookup("A/C/E", LOOKUP_PARENT) ok lookup_create("A/C/E") mutex_lock("A/C") ok configfs_mkdir("A/C/E") ok detach_item("A/C") d_delete("A/C") mutex_unlock("A") detach_groups("A") mutex_lock("A/B") detach_group("A/B") detach_groups("A/B") nothing since no _default_ group detach_item("A/B") mutex_unlock("A/B") d_delete("A/B") detach_item("A") d_delete("A") Two bugs: 1/ "A/B/C" and "A/C/E" are created, but never removed while their parent are removed in the end. The same could happen with symlink() instead of mkdir(). 2/ "A" and "A/C" inodes are not locked while detach_item() is called on them, which may probably confuse VFS. This commit fixes 1/, tagging new directories with CONFIGFS_USET_CREATING before building the inode and instantiating the dentry, and validating the whole group+default groups hierarchy in a second pass by clearing CONFIGFS_USET_CREATING. mkdir(), symlink(), lookup(), and dir_open() simply return -ENOENT if called in (or linking to) a directory tagged with CONFIGFS_USET_CREATING. This does not prevent userspace from calling stat() successfuly on such directories, but this prevents userspace from adding (children to | symlinking from/to | read/write attributes of | listing the contents of) not validated items. In other words, userspace will not interact with the subsystem on a new item until the new item creation completes correctly. It was first proposed to re-use CONFIGFS_USET_IN_MKDIR instead of a new flag CONFIGFS_USET_CREATING, but this generated conflicts when checking the target of a new symlink: a valid target directory in the middle of attaching a new user-created child item could be wrongly detected as being attached. 2/ is fixed by next commit. Signed-off-by: Louis Rilling <louis.rilling@kerlabs.com> Signed-off-by: Joel Becker <joel.becker@oracle.com> Signed-off-by: Mark Fasheh <mfasheh@suse.com>
2008-07-31[PATCH] configfs: Fix failing symlink() making rmdir() failLouis Rilling1-0/+10
On a similar pattern as mkdir() vs rmdir(), a failing symlink() may make rmdir() fail for the symlink's parent and the symlink's target as well. failing symlink() making target's rmdir() fail: process 1: process 2: symlink("A/S" -> "B") allow_link() create_link() attach to "B" links list rmdir("B") detach_prep("B") error because of new link configfs_create_link("A", "S") error (eg -ENOMEM) failing symlink() making parent's rmdir() fail: process 1: process 2: symlink("A/D/S" -> "B") allow_link() create_link() attach to "B" links list configfs_create_link("A/D", "S") make_dirent("A/D", "S") rmdir("A") detach_prep("A") detach_prep("A/D") error because of "S" create("S") error (eg -ENOMEM) We cannot use the same solution as for mkdir() vs rmdir(), since rmdir() on the target cannot wait on the i_mutex of the new symlink's parent without risking a deadlock (with other symlink() or sys_rename()). Instead we define a global mutex protecting all configfs symlinks attachment, so that rmdir() can avoid the races above. Signed-off-by: Louis Rilling <louis.rilling@kerlabs.com> Signed-off-by: Joel Becker <joel.becker@oracle.com> Signed-off-by: Mark Fasheh <mfasheh@suse.com>
2008-07-31[PATCH] configfs: Fix symlink() to a removing itemLouis Rilling1-7/+7
The rule for configfs symlinks is that symlinks always point to valid config_items, and prevent the target from being removed. However, configfs_symlink() only checks that it can grab a reference on the target item, without ensuring that it remains alive until the symlink is correctly attached. This patch makes configfs_symlink() fail whenever the target is being removed, using the CONFIGFS_USET_DROPPING flag set by configfs_detach_prep() and protected by configfs_dirent_lock. This patch introduces a similar (weird?) behavior as with mkdir failures making rmdir fail: if symlink() races with rmdir() of the parent directory (or its youngest user-created ancestor if parent is a default group) or rmdir() of the target directory, and then fails in configfs_create(), this can make the racing rmdir() fail despite the concerned directory having no user-created entry (resp. no symlink pointing to it or one of its default groups) in the end. This behavior is fixed in later patches. Signed-off-by: Louis Rilling <louis.rilling@kerlabs.com> Signed-off-by: Joel Becker <joel.becker@oracle.com> Signed-off-by: Mark Fasheh <mfasheh@suse.com>
2008-07-31[PATCH] configfs: Include linux/err.h in linux/configfs.hJoel Becker1-1/+1
We now use PTR_ERR() in the ->make_item() and ->make_group() operations. Folks including configfs.h need err.h. Signed-off-by: Joel Becker <joel.becker@oracle.com> Signed-off-by: Mark Fasheh <mfasheh@suse.com>
2008-07-17configfs: Allow ->make_item() and ->make_group() to return detailed errors.Joel Becker1-10/+15
The configfs operations ->make_item() and ->make_group() currently return a new item/group. A return of NULL signifies an error. Because of this, -ENOMEM is the only return code bubbled up the stack. Multiple folks have requested the ability to return specific error codes when these operations fail. This patch adds that ability by changing the ->make_item/group() ops to return ERR_PTR() values. These errors are bubbled up appropriately. NULL returns are changed to -ENOMEM for compatibility. Also updated are the in-kernel users of configfs. This is a rework of reverted commit 11c3b79218390a139f2d474ee1e983a672d5839a. Signed-off-by: Joel Becker <joel.becker@oracle.com>
2008-07-17Revert "configfs: Allow ->make_item() and ->make_group() to return detailed ↵Joel Becker1-6/+7
errors." This reverts commit 11c3b79218390a139f2d474ee1e983a672d5839a. The code will move to PTR_ERR(). Signed-off-by: Joel Becker <joel.becker@oracle.com>
2008-07-14configfs: Allow ->make_item() and ->make_group() to return detailed errors.Joel Becker1-7/+6
The configfs operations ->make_item() and ->make_group() currently return a new item/group. A return of NULL signifies an error. Because of this, -ENOMEM is the only return code bubbled up the stack. Multiple folks have requested the ability to return specific error codes when these operations fail. This patch adds that ability by changing the ->make_item/group() ops to return an int. Also updated are the in-kernel users of configfs. Signed-off-by: Joel Becker <joel.becker@oracle.com>
2008-07-14configfs: Fix failing mkdir() making racing rmdir() failLouis Rilling1-10/+43
When fixing the rename() vs rmdir() deadlock, we stopped locking default groups' inodes in configfs_detach_prep(), letting racing mkdir() in default groups proceed concurrently. This enables races like below happen, which leads to a failing mkdir() making rmdir() fail, despite the group to remove having no user-created directory under it in the end. process A: process B: /* PWD=A/B */ mkdir("C") make_item("C") attach_group("C") rmdir("A") detach_prep("A") detach_prep("B") error because of "C" return -ENOTEMPTY attach_group("C/D") error (eg -ENOMEM) return -ENOMEM This patch prevents such scenarii by making rmdir() wait as long as detach_prep() fails because a racing mkdir() is in the middle of attach_group(). To achieve this, mkdir() sets a flag CONFIGFS_USET_IN_MKDIR in parent's configfs_dirent before calling attach_group(), and clears the flag once attach_group() is done. detach_prep() fails with -EAGAIN whenever the flag is hit and returns the guilty inode's mutex so that rmdir() can wait on it. Signed-off-by: Louis Rilling <Louis.Rilling@kerlabs.com> Signed-off-by: Joel Becker <joel.becker@oracle.com>
2008-07-14configfs: Fix deadlock with racing rmdir() and rename()Louis Rilling1-20/+25
This patch fixes the deadlock between racing sys_rename() and configfs_rmdir(). The idea is to avoid locking i_mutexes of default groups in configfs_detach_prep(), and rely instead on the new configfs_dirent_lock to protect against configfs_dirent's linkage mutations. To ensure that an mkdir() racing with rmdir() will not create new items in a to-be-removed default group, we make configfs_new_dirent() check for the CONFIGFS_USET_DROPPING flag right before linking the new dirent, and return error if the flag is set. This makes racing mkdir()/symlink()/dir_open() fail in places where errors could already happen, resp. in (attach_item()|attach_group())/create_link()/new_dirent(). configfs_depend() remains safe since it locks all the path from configfs root, and is thus mutually exclusive with rmdir(). An advantage of this is that now detach_groups() unconditionnaly takes the default groups i_mutex, which makes it more consistent with populate_groups(). Signed-off-by: Louis Rilling <Louis.Rilling@kerlabs.com> Signed-off-by: Joel Becker <joel.becker@oracle.com>
2008-07-14configfs: Make configfs_new_dirent() return error code instead of NULLLouis Rilling1-4/+5
This patch makes configfs_new_dirent return negative error code instead of NULL, which will be useful in the next patch to differentiate ENOMEM from ENOENT. Signed-off-by: Louis Rilling <Louis.Rilling@kerlabs.com> Signed-off-by: Joel Becker <joel.becker@oracle.com>
2008-07-14configfs: Protect configfs_dirent s_links list mutationsLouis Rilling1-2/+3
Symlinks to a config_item are listed under its configfs_dirent s_links, but the list mutations are not protected by any common lock. This patch uses the configfs_dirent_lock spinlock to add the necessary protection. Note: we should also protect the list_empty() test in configfs_detach_prep() but 1/ the lock should not be released immediately because nothing would prevent the list from being filled after a successful list_empty() test, making the problem tricky, 2/ this will be solved by the rmdir() vs rename() deadlock bugfix. Signed-off-by: Louis Rilling <Louis.Rilling@kerlabs.com> Signed-off-by: Joel Becker <joel.becker@oracle.com>
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-06 04:19:11 +0000