From: Al Viro <viro@zeniv.linux.org.uk>
Date: Tue, 26 Mar 2019 01:39:50 +0000 (+0000)
Subject: jffs2: fix use-after-free on symlink traversal
X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=4fdcfab5b5537c21891e22e65996d4d0dd8ab4ca;p=openwrt%2Fstaging%2Fblogic.git

jffs2: fix use-after-free on symlink traversal

free the symlink body after the same RCU delay we have for freeing the
struct inode itself, so that traversal during RCU pathwalk wouldn't step
into freed memory.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---

diff --git a/fs/jffs2/readinode.c b/fs/jffs2/readinode.c
index 389ea53ea487..bccfc40b3a74 100644
--- a/fs/jffs2/readinode.c
+++ b/fs/jffs2/readinode.c
@@ -1414,11 +1414,6 @@ void jffs2_do_clear_inode(struct jffs2_sb_info *c, struct jffs2_inode_info *f)
 
 	jffs2_kill_fragtree(&f->fragtree, deleted?c:NULL);
 
-	if (f->target) {
-		kfree(f->target);
-		f->target = NULL;
-	}
-
 	fds = f->dents;
 	while(fds) {
 		fd = fds;
diff --git a/fs/jffs2/super.c b/fs/jffs2/super.c
index bb6ae387469f..05d892c79339 100644
--- a/fs/jffs2/super.c
+++ b/fs/jffs2/super.c
@@ -47,7 +47,10 @@ static struct inode *jffs2_alloc_inode(struct super_block *sb)
 static void jffs2_i_callback(struct rcu_head *head)
 {
 	struct inode *inode = container_of(head, struct inode, i_rcu);
-	kmem_cache_free(jffs2_inode_cachep, JFFS2_INODE_INFO(inode));
+	struct jffs2_inode_info *f = JFFS2_INODE_INFO(inode);
+
+	kfree(f->target);
+	kmem_cache_free(jffs2_inode_cachep, f);
 }
 
 static void jffs2_destroy_inode(struct inode *inode)