jffs2: fix use-after-free on symlink traversal

BugLink: https://bugs.launchpad.net/bugs/1832775
[ Upstream commit 4fdcfab5b5537c21891e22e65996d4d0dd8ab4ca ]

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>
Signed-off-by: Sasha Levin (Microsoft) <sashal@kernel.org>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

diff --git a/fs/jffs2/readinode.c b/fs/jffs2/readinode.c
index 389ea53ea487538061ff3b6da78e27df2f894ac1..bccfc40b3a74ab002e45a07149afbe09634d8f64 100644 (file)
--- 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 bb6ae387469f4d020424bfb13333e24d84e68123..05d892c79339f97276c81337c26929d8f53b7db2 100644 (file)
--- 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)