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    Subject[RFC PATCH 02/62] apparmorfs: fix use-after-free on symlink traversal
    Date
    From: Al Viro <viro@zeniv.linux.org.uk>

    symlink body shouldn't be freed without an RCU delay. Switch apparmorfs
    to ->destroy_inode() and use of call_rcu(); free both the inode and symlink
    body in the callback.

    Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
    ---
    security/apparmor/apparmorfs.c | 13 +++++++++----
    1 file changed, 9 insertions(+), 4 deletions(-)

    diff --git a/security/apparmor/apparmorfs.c b/security/apparmor/apparmorfs.c
    index fefee040bf79..b9298d2e8165 100644
    --- a/security/apparmor/apparmorfs.c
    +++ b/security/apparmor/apparmorfs.c
    @@ -123,17 +123,22 @@ static int aafs_show_path(struct seq_file *seq, struct dentry *dentry)
    return 0;
    }

    -static void aafs_evict_inode(struct inode *inode)
    +static void aafs_i_callback(struct rcu_head *head)
    {
    - truncate_inode_pages_final(&inode->i_data);
    - clear_inode(inode);
    + struct inode *inode = container_of(head, struct inode, i_rcu);
    if (S_ISLNK(inode->i_mode))
    kfree(inode->i_link);
    + free_inode_nonrcu(inode);
    +}
    +
    +static void aafs_destroy_inode(struct inode *inode)
    +{
    + call_rcu(&inode->i_rcu, aafs_i_callback);
    }

    static const struct super_operations aafs_super_ops = {
    .statfs = simple_statfs,
    - .evict_inode = aafs_evict_inode,
    + .destroy_inode = aafs_destroy_inode,
    .show_path = aafs_show_path,
    };

    --
    2.11.0
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