From e8f077c8831528e2ec1ea6c8ba090e405fdcd0b7 Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Sat, 7 Nov 2009 23:27:01 -0800 Subject: [PATCH] sysfs: Use dentry_ops instead of directly playing with the dcache 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 Acked-by: Serge Hallyn Signed-off-by: Eric W. Biederman Signed-off-by: Greg Kroah-Hartman --- fs/sysfs/dir.c | 73 +++++++++++++++++++++++++++++++------------------- 1 file changed, 46 insertions(+), 27 deletions(-) diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c index 01a9a64ecd4e..9ee130be03be 100644 --- a/fs/sysfs/dir.c +++ b/fs/sysfs/dir.c @@ -298,6 +298,46 @@ void release_sysfs_dirent(struct sysfs_dirent * sd) 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) { 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 = { + .d_revalidate = sysfs_dentry_revalidate, + .d_delete = sysfs_dentry_delete, .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 * - * 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 * up anymore. */ -static void sysfs_drop_dentry(struct sysfs_dirent *sd) +static void sysfs_dec_nlink(struct sysfs_dirent *sd) { struct inode *inode; - struct dentry *dentry; inode = ilookup(sysfs_sb, sd->s_ino); if (!inode) 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 */ mutex_lock(&inode->i_mutex); @@ -611,7 +630,7 @@ void sysfs_addrm_finish(struct sysfs_addrm_cxt *acxt) acxt->removed = sd->s_sibling; sd->s_sibling = NULL; - sysfs_drop_dentry(sd); + sysfs_dec_nlink(sd); sysfs_deactivate(sd); unmap_bin_file(sd); sysfs_put(sd);