From: Sishuai Gong <sishuai@purdue.edu> mainline inclusion from mainline-v5.15-rc1 commit c42dd069be8dfc9b2239a5c89e73bbd08ab35de0 category: bugfix bugzilla: 187567, https://gitee.com/openeuler/kernel/issues/I5PK1G CVE: NA Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/fs... -------------------------------- 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@purdue.edu> Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com> Reviewed-by: Zhang Yi <yi.zhang@huawei.com> Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com> --- 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 31749d06bde2..cefa4e48278e 100644 --- a/fs/configfs/dir.c +++ b/fs/configfs/dir.c @@ -448,13 +448,13 @@ 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); @@ -471,10 +471,11 @@ 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; } -- 2.20.1