From: Sishuai Gong <sishuai@xxxxxxxxxx>
When configfs_lookup() is executing list_for_each_entry(),
it is possible that configfs_dir_lseek() is calling list_del().
Some unfortunate interleavings of them can cause a kernel NULL
pointer dereference error
Thread 1 Thread 2
//configfs_dir_lseek() //configfs_lookup()
list_del(&cursor->s_sibling);
list_for_each_entry(sd, ...)
Fix this by grabbing configfs_dirent_lock in configfs_lookup()
while iterating ->s_children.
Signed-off-by: Sishuai Gong <sishuai@xxxxxxxxxx>
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
fs/configfs/dir.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
index fc20bd8a6337..1466b5d01cbb 100644
--- a/fs/configfs/dir.c
+++ b/fs/configfs/dir.c
@@ -439,13 +439,13 @@ static struct dentry * configfs_lookup(struct inode *dir,
if (!configfs_dirent_is_ready(parent_sd))
return ERR_PTR(-ENOENT);
+ spin_lock(&configfs_dirent_lock);
list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
if ((sd->s_type & CONFIGFS_NOT_PINNED) &&
!strcmp(configfs_get_name(sd), dentry->d_name.name)) {
struct configfs_attribute *attr = sd->s_element;
umode_t mode = (attr->ca_mode & S_IALLUGO) | S_IFREG;
- spin_lock(&configfs_dirent_lock);
dentry->d_fsdata = configfs_get(sd);
sd->s_dentry = dentry;
spin_unlock(&configfs_dirent_lock);
@@ -462,10 +462,11 @@ static struct dentry * configfs_lookup(struct inode *dir,
inode->i_size = PAGE_SIZE;
inode->i_fop = &configfs_file_operations;
}
- break;
+ goto done;
}
}
-
+ spin_unlock(&configfs_dirent_lock);
+done:
d_add(dentry, inode);
return NULL;
}
--
2.30.2
