It turns out we have been being silly and have failed to
protect ourselves against races between sysfs_lookup
and operations that modify the sysfs directory like sysfs_readdir
and create_dir.
So this patch modifies sysfs_lookup to grab sysfs_mutex before
walking the parent->s_children list.
Signed-off-by: Eric W. Biederman <[EMAIL PROTECTED]>
---
fs/sysfs/dir.c | 15 +++++++++------
1 files changed, 9 insertions(+), 6 deletions(-)
diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index 40b9efe..b27a38c 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -756,11 +756,13 @@ static struct dentry * sysfs_lookup(struct inode *dir,
struct dentry *dentry,
struct nameidata *nd)
{
struct sysfs_dirent * parent_sd = dentry->d_parent->d_fsdata;
+ struct dentry *result = NULL;
struct sysfs_dirent * sd;
struct bin_attribute *bin_attr;
struct inode *inode;
int found = 0;
+ mutex_lock(&sysfs_mutex);
for (sd = parent_sd->s_children; sd; sd = sd->s_sibling) {
if (sysfs_type(sd) &&
!strcmp(sd->s_name, dentry->d_name.name)) {
@@ -771,14 +773,14 @@ static struct dentry * sysfs_lookup(struct inode *dir,
struct dentry *dentry,
/* no such entry */
if (!found)
- return NULL;
+ goto out;
/* attach dentry and inode */
inode = sysfs_get_inode(sd);
- if (!inode)
- return ERR_PTR(-ENOMEM);
-
- mutex_lock(&sysfs_mutex);
+ if (!inode) {
+ result = ERR_PTR(-ENOMEM);
+ goto out;
+ }
if (inode->i_state & I_NEW) {
/* initialize inode according to type */
@@ -808,9 +810,10 @@ static struct dentry * sysfs_lookup(struct inode *dir,
struct dentry *dentry,
sysfs_instantiate(dentry, inode);
sysfs_attach_dentry(sd, dentry);
+out:
mutex_unlock(&sysfs_mutex);
- return NULL;
+ return result;
}
const struct inode_operations sysfs_dir_inode_operations = {
--
1.5.1.1.181.g2de0
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