| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-Id: <20210823194318.17528-1-sishuai@purdue.edu>
Date: Mon, 23 Aug 2021 15:43:18 -0400
From: sishuaigong <sishuai@...due.edu>
To: jlbec@...lplan.org, hch@....de
Cc: linux-kernel@...r.kernel.org, sishuaigong <sishuai@...due.edu>
Subject: [PATCH v2] configfs: fix a race in configfs_lookup()
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 bug by grabbing configfs_dirent_lock in configfs_lookup().
Reported-by: Sishuai Gong <sishuai@...due.edu>
Signed-off-by: sishuaigong <sishuai@...due.edu>
---
fs/configfs/dir.c | 86 +++++++++++++++++++----------------------------
1 file changed, 35 insertions(+), 51 deletions(-)
diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
index ac5e0c0e9181..c9af54f75051 100644
--- a/fs/configfs/dir.c
+++ b/fs/configfs/dir.c
@@ -417,44 +417,13 @@ static void configfs_remove_dir(struct config_item * item)
dput(dentry);
}
-
-/* attaches attribute's configfs_dirent to the dentry corresponding to the
- * attribute file
- */
-static int configfs_attach_attr(struct configfs_dirent * sd, struct dentry * dentry)
-{
- struct configfs_attribute * attr = sd->s_element;
- struct inode *inode;
-
- spin_lock(&configfs_dirent_lock);
- dentry->d_fsdata = configfs_get(sd);
- sd->s_dentry = dentry;
- spin_unlock(&configfs_dirent_lock);
-
- inode = configfs_create(dentry, (attr->ca_mode & S_IALLUGO) | S_IFREG);
- if (IS_ERR(inode)) {
- configfs_put(sd);
- return PTR_ERR(inode);
- }
- if (sd->s_type & CONFIGFS_ITEM_BIN_ATTR) {
- inode->i_size = 0;
- inode->i_fop = &configfs_bin_file_operations;
- } else {
- inode->i_size = PAGE_SIZE;
- inode->i_fop = &configfs_file_operations;
- }
- d_add(dentry, inode);
- return 0;
-}
-
static struct dentry * configfs_lookup(struct inode *dir,
struct dentry *dentry,
unsigned int flags)
{
struct configfs_dirent * parent_sd = dentry->d_parent->d_fsdata;
struct configfs_dirent * sd;
- int found = 0;
- int err;
+ struct inode *inode = NULL;
/*
* Fake invisibility if dir belongs to a group/default groups hierarchy
@@ -464,38 +433,53 @@ static struct dentry * configfs_lookup(struct inode *dir,
* not complete their initialization, since the dentries of the
* attributes won't be instantiated.
*/
- err = -ENOENT;
if (!configfs_dirent_is_ready(parent_sd))
- goto out;
+ 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) {
- const unsigned char * name = configfs_get_name(sd);
-
+ const unsigned char *name = configfs_get_name(sd);
if (strcmp(name, dentry->d_name.name))
continue;
- found = 1;
- err = configfs_attach_attr(sd, dentry);
- break;
- }
- }
+ struct configfs_attribute *attr = sd->s_element;
+ umode_t mode = (attr->ca_mode & S_IALLUGO) | S_IFREG;
- if (!found) {
- /*
- * If it doesn't exist and it isn't a NOT_PINNED item,
- * it must be negative.
- */
- if (dentry->d_name.len > NAME_MAX)
- return ERR_PTR(-ENAMETOOLONG);
- d_add(dentry, NULL);
- return NULL;
+ dentry->d_fsdata = configfs_get(sd);
+ sd->s_dentry = dentry;
+
+ spin_unlock(&configfs_dirent_lock);
+
+ inode = configfs_create(dentry, mode);
+ if (IS_ERR(inode)) {
+ configfs_put(sd);
+ return ERR_CAST(inode);
+ }
+ if (sd->s_type & CONFIGFS_ITEM_BIN_ATTR) {
+ inode->i_size = 0;
+ inode->i_fop = &configfs_bin_file_operations;
+ } else {
+ inode->i_size = PAGE_SIZE;
+ inode->i_fop = &configfs_file_operations;
+ }
+ goto out;
+ }
}
+ spin_unlock(&configfs_dirent_lock);
+ /*
+ * If it doesn't exist and it isn't a NOT_PINNED item,
+ * it must be negative.
+ */
+ if (dentry->d_name.len > NAME_MAX)
+ return ERR_PTR(-ENAMETOOLONG);
out:
- return ERR_PTR(err);
+ d_add(dentry, inode);
+ return NULL;
}
+
/*
* Only subdirectories count here. Files (CONFIGFS_NOT_PINNED) are
* attributes and are removed by rmdir(). We recurse, setting
--
2.17.1
Powered by blists - more mailing lists