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authorJoel Becker <jlbec@evilplan.org>2011-05-18 04:08:16 -0700
committerJoel Becker <jlbec@evilplan.org>2011-05-18 04:08:16 -0700
commit24307aa1e707b31613be92deaba7990e16bc1aec (patch)
tree6699c969a7f56c2b7949bf16af54320caee0687e
parentdf7f99670a4c76f269ae57ce91876b309417a316 (diff)
downloadlinux-stericsson-24307aa1e707b31613be92deaba7990e16bc1aec.tar.gz
configfs: Fix race between configfs_readdir() and configfs_d_iput()
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>
-rw-r--r--fs/configfs/dir.c33
1 files changed, 28 insertions, 5 deletions
diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
index b11d7342eef2..9a37a9b6de3a 100644
--- a/fs/configfs/dir.c
+++ b/fs/configfs/dir.c
@@ -53,11 +53,14 @@ DEFINE_SPINLOCK(configfs_dirent_lock);
static void configfs_d_iput(struct dentry * dentry,
struct inode * inode)
{
- struct configfs_dirent * sd = dentry->d_fsdata;
+ struct configfs_dirent *sd = dentry->d_fsdata;
if (sd) {
BUG_ON(sd->s_dentry != dentry);
+ /* Coordinate with configfs_readdir */
+ spin_lock(&configfs_dirent_lock);
sd->s_dentry = NULL;
+ spin_unlock(&configfs_dirent_lock);
configfs_put(sd);
}
iput(inode);
@@ -1546,7 +1549,7 @@ static int configfs_readdir(struct file * filp, void * dirent, filldir_t filldir
struct configfs_dirent * parent_sd = dentry->d_fsdata;
struct configfs_dirent *cursor = filp->private_data;
struct list_head *p, *q = &cursor->s_sibling;
- ino_t ino;
+ ino_t ino = 0;
int i = filp->f_pos;
switch (i) {
@@ -1574,6 +1577,7 @@ static int configfs_readdir(struct file * filp, void * dirent, filldir_t filldir
struct configfs_dirent *next;
const char * name;
int len;
+ struct inode *inode = NULL;
next = list_entry(p, struct configfs_dirent,
s_sibling);
@@ -1582,9 +1586,28 @@ static int configfs_readdir(struct file * filp, void * dirent, filldir_t filldir
name = configfs_get_name(next);
len = strlen(name);
- if (next->s_dentry)
- ino = next->s_dentry->d_inode->i_ino;
- else
+
+ /*
+ * We'll have a dentry and an inode for
+ * PINNED items and for open attribute
+ * files. We lock here to prevent a race
+ * with configfs_d_iput() clearing
+ * s_dentry before calling iput().
+ *
+ * Why do we go to the trouble? If
+ * someone has an attribute file open,
+ * the inode number should match until
+ * they close it. Beyond that, we don't
+ * care.
+ */
+ spin_lock(&configfs_dirent_lock);
+ dentry = next->s_dentry;
+ if (dentry)
+ inode = dentry->d_inode;
+ if (inode)
+ ino = inode->i_ino;
+ spin_unlock(&configfs_dirent_lock);
+ if (!inode)
ino = iunique(configfs_sb, 2);
if (filldir(dirent, name, len, filp->f_pos, ino,