Smack: File receive for sockets

The existing file receive hook checks for access on
the file inode even for UDS. This is not right, as
the inode is not used by Smack to make access checks
for sockets. This change checks for an appropriate
access relationship between the receiving (current)
process and the socket. If the process can't write
to the socket's send label or the socket's receive
label can't write to the process fail.

This will allow the legitimate cases, where the
socket sender and socket receiver can freely communicate.
Only strangly set socket labels should cause a problem.

Change-Id: Id37df53243264ac843f9c6693ba99aba9779f05e
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
[backport to 3.10 from smack-next commit 79be093500791cc25cc31bcaec5a4db62e21497b]
Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
(cherry picked from commit 4306b30a4c4c787144fb7ff71ffe44799c9386dd)
Signed-off-by: Sooyoung Ha <yoosah.ha@samsung.com>

diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index ea4ae19524f418a3030f3a29e125984b39b32a82..61291e543ca1bb0942c27167ac3bd882ca568019 100644 (file)
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -1664,9 +1664,30 @@ static int smack_file_receive(struct file *file)
        int rc;
        int may = 0;
        struct smk_audit_info ad;
+       struct inode *inode = file_inode(file);
+       struct socket *sock;
+       struct task_smack *tsp;
+       struct socket_smack *ssp;
 
        smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_PATH);
        smk_ad_setfield_u_fs_path(&ad, file->f_path);
+
+       if (S_ISSOCK(inode->i_mode)) {
+               sock = SOCKET_I(inode);
+               ssp = sock->sk->sk_security;
+               tsp = current_security();
+               /*
+                * If the receiving process can't write to the
+                * passed socket or if the passed socket can't
+                * write to the receiving process don't accept
+                * the passed socket.
+                */
+               rc = smk_access(tsp->smk_task, ssp->smk_out->smk_known, MAY_WRITE, &ad);
+               if (rc < 0)
+                       return rc;
+               rc = smk_access(ssp->smk_in, tsp->smk_task->smk_known, MAY_WRITE, &ad);
+               return rc;
+       }
        /*
         * This code relies on bitmasks.
         */