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authorSishuai Gong <sishuai@purdue.edu>2021-08-25 08:52:20 +0300
committerChristoph Hellwig <hch@lst.de>2021-08-25 08:58:49 +0300
commitc42dd069be8dfc9b2239a5c89e73bbd08ab35de0 (patch)
treee537efef13add0360bd77adb2818a56a318eea42 /fs/configfs
parentd07f132a225c013e59aa77f514ad9211ecab82ee (diff)
downloadlinux-c42dd069be8dfc9b2239a5c89e73bbd08ab35de0.tar.xz
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 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>
Diffstat (limited to 'fs/configfs')
-rw-r--r--fs/configfs/dir.c7
1 files 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;
}