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sysfs: Use dentry_ops instead of directly playing with the dcache

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Calling d_drop unconditionally when a sysfs_dirent is deleted has
the potential to leak mounts, so instead implement dentry delete
and revalidate operations that cause sysfs dentries to be removed
at the appropriate time.

Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Eric W. Biederman <ebiederm@aristanetworks.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Eric W. Biederman 2009-11-07 23:27:01 -08:00 committed by Greg Kroah-Hartman
parent 28a027cfc0
commit e8f077c883
1 changed files with 46 additions and 27 deletions
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73
fs/sysfs/dir.c
View File

@ -298,6 +298,46 @@ void release_sysfs_dirent(struct sysfs_dirent * sd)
goto repeat; goto repeat;
} }
static int sysfs_dentry_delete(struct dentry *dentry)
{
struct sysfs_dirent *sd = dentry->d_fsdata;
return !!(sd->s_flags & SYSFS_FLAG_REMOVED);
}
static int sysfs_dentry_revalidate(struct dentry *dentry, struct nameidata *nd)
{
struct sysfs_dirent *sd = dentry->d_fsdata;
int is_dir;
mutex_lock(&sysfs_mutex);
/* The sysfs dirent has been deleted */
if (sd->s_flags & SYSFS_FLAG_REMOVED)
goto out_bad;
mutex_unlock(&sysfs_mutex);
out_valid:
return 1;
out_bad:
/* Remove the dentry from the dcache hashes.
* If this is a deleted dentry we use d_drop instead of d_delete
* so sysfs doesn't need to cope with negative dentries.
*/
is_dir = (sysfs_type(sd) == SYSFS_DIR);
mutex_unlock(&sysfs_mutex);
if (is_dir) {
/* If we have submounts we must allow the vfs caches
* to lie about the state of the filesystem to prevent
* leaks and other nasty things.
*/
if (have_submounts(dentry))
goto out_valid;
shrink_dcache_parent(dentry);
}
d_drop(dentry);
return 0;
}
static void sysfs_dentry_iput(struct dentry *dentry, struct inode *inode) static void sysfs_dentry_iput(struct dentry *dentry, struct inode *inode)
{ {
struct sysfs_dirent * sd = dentry->d_fsdata; struct sysfs_dirent * sd = dentry->d_fsdata;
@ -307,6 +347,8 @@ static void sysfs_dentry_iput(struct dentry *dentry, struct inode *inode)
} }
static const struct dentry_operations sysfs_dentry_ops = { static const struct dentry_operations sysfs_dentry_ops = {
.d_revalidate = sysfs_dentry_revalidate,
.d_delete = sysfs_dentry_delete,
.d_iput = sysfs_dentry_iput, .d_iput = sysfs_dentry_iput,
}; };
@ -527,44 +569,21 @@ void sysfs_remove_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd)
} }
/** /**
* sysfs_drop_dentry - drop dentry for the specified sysfs_dirent * sysfs_dec_nlink - Decrement link count for the specified sysfs_dirent
* @sd: target sysfs_dirent * @sd: target sysfs_dirent
* *
* Drop dentry for @sd. @sd must have been unlinked from its * Decrement nlink for @sd. @sd must have been unlinked from its
* parent on entry to this function such that it can't be looked * parent on entry to this function such that it can't be looked
* up anymore. * up anymore.
*/ */
static void sysfs_drop_dentry(struct sysfs_dirent *sd) static void sysfs_dec_nlink(struct sysfs_dirent *sd)
{ {
struct inode *inode; struct inode *inode;
struct dentry *dentry;
inode = ilookup(sysfs_sb, sd->s_ino); inode = ilookup(sysfs_sb, sd->s_ino);
if (!inode) if (!inode)
return; return;
/* Drop any existing dentries associated with sd.
*
* For the dentry to be properly freed we need to grab a
* reference to the dentry under the dcache lock, unhash it,
* and then put it. The playing with the dentry count allows
* dput to immediately free the dentry if it is not in use.
*/
repeat:
spin_lock(&dcache_lock);
list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
if (d_unhashed(dentry))
continue;
dget_locked(dentry);
spin_lock(&dentry->d_lock);
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
dput(dentry);
goto repeat;
}
spin_unlock(&dcache_lock);
/* adjust nlink and update timestamp */ /* adjust nlink and update timestamp */
mutex_lock(&inode->i_mutex); mutex_lock(&inode->i_mutex);
@ -611,7 +630,7 @@ void sysfs_addrm_finish(struct sysfs_addrm_cxt *acxt)
acxt->removed = sd->s_sibling; acxt->removed = sd->s_sibling;
sd->s_sibling = NULL; sd->s_sibling = NULL;
sysfs_drop_dentry(sd); sysfs_dec_nlink(sd);
sysfs_deactivate(sd); sysfs_deactivate(sd);
unmap_bin_file(sd); unmap_bin_file(sd);
sysfs_put(sd); sysfs_put(sd);