[PATCH AUTOSEL 4.14 16/35] jffs2: fix use-after-free on symlink traversal

Sasha Levin
2019-04-24T14:58:02Z

From: Al Viro <viro@zeniv.linux.org.uk>

[ 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 <sashal@kernel.org>
---
fs/jffs2/readinode.c | 5 -----
fs/jffs2/super.c | 5 ++++-
2 files changed, 4 insertions(+), 6 deletions(-)

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 83340496645b..9a9f30eddbbb 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)
--
2.19.1