user namespace: usb: make usb urbs user namespace aware (v2)

Add to the dev_state and alloc_async structures the user namespace
corresponding to the uid and euid.  Pass these to kill_pid_info_as_uid(),
which can then implement a proper, user-namespace-aware uid check.

Changelog:
Sep 20: Per Oleg's suggestion: Instead of caching and passing user namespace,
	uid, and euid each separately, pass a struct cred.
Sep 26: Address Alan Stern's comments: don't define a struct cred at
	usbdev_open(), and take and put a cred at async_completed() to
	ensure it lasts for the duration of kill_pid_info_as_cred().

Signed-off-by: Serge Hallyn <serge.hallyn@canonical.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

3 files changed, 31 insertions, 26 deletions

diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index 0ca54e22d319..e3beaf229ee3 100644
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -46,6 +46,7 @@
 #include <linux/cdev.h>
 #include <linux/notifier.h>
 #include <linux/security.h>
+#include <linux/user_namespace.h>
 #include <asm/uaccess.h>
 #include <asm/byteorder.h>
 #include <linux/moduleparam.h>
@@ -68,7 +69,7 @@ struct dev_state {
         wait_queue_head_t wait;     /* wake up if a request completed */
         unsigned int discsignr;
         struct pid *disc_pid;
-        uid_t disc_uid, disc_euid;
+        const struct cred *cred;
         void __user *disccontext;
         unsigned long ifclaimed;
         u32 secid;
@@ -79,7 +80,7 @@ struct async {
         struct list_head asynclist;
         struct dev_state *ps;
         struct pid *pid;
-        uid_t uid, euid;
+        const struct cred *cred;
         unsigned int signr;
         unsigned int ifnum;
         void __user *userbuffer;
@@ -248,6 +249,7 @@ static struct async *alloc_async(unsigned int numisoframes)
 static void free_async(struct async *as)
 {
         put_pid(as->pid);
+        put_cred(as->cred);
         kfree(as->urb->transfer_buffer);
         kfree(as->urb->setup_packet);
         usb_free_urb(as->urb);
@@ -393,9 +395,8 @@ static void async_completed(struct urb *urb)
         struct dev_state *ps = as->ps;
         struct siginfo sinfo;
         struct pid *pid = NULL;
-        uid_t uid = 0;
-        uid_t euid = 0;
         u32 secid = 0;
+        const struct cred *cred = NULL;
         int signr;
 
         spin_lock(&ps->lock);
@@ -408,8 +409,7 @@ static void async_completed(struct urb *urb)
                 sinfo.si_code = SI_ASYNCIO;
                 sinfo.si_addr = as->userurb;
                 pid = get_pid(as->pid);
-                uid = as->uid;
-                euid = as->euid;
+                cred = get_cred(as->cred);
                 secid = as->secid;
         }
         snoop(&urb->dev->dev, "urb complete\n");
@@ -423,9 +423,9 @@ static void async_completed(struct urb *urb)
         spin_unlock(&ps->lock);
 
         if (signr) {
-                kill_pid_info_as_uid(sinfo.si_signo, &sinfo, pid, uid,
-                                      euid, secid);
+                kill_pid_info_as_cred(sinfo.si_signo, &sinfo, pid, cred, secid);
                 put_pid(pid);
+                put_cred(cred);
         }
 
         wake_up(&ps->wait);
@@ -672,7 +672,6 @@ static int usbdev_open(struct inode *inode, struct file *file)
 {
         struct usb_device *dev = NULL;
         struct dev_state *ps;
-        const struct cred *cred = current_cred();
         int ret;
 
         ret = -ENOMEM;
@@ -722,8 +721,7 @@ static int usbdev_open(struct inode *inode, struct file *file)
         init_waitqueue_head(&ps->wait);
         ps->discsignr = 0;
         ps->disc_pid = get_pid(task_pid(current));
-        ps->disc_uid = cred->uid;
-        ps->disc_euid = cred->euid;
+        ps->cred = get_current_cred();
         ps->disccontext = NULL;
         ps->ifclaimed = 0;
         security_task_getsecid(current, &ps->secid);
@@ -765,6 +763,7 @@ static int usbdev_release(struct inode *inode, struct file *file)
         usb_unlock_device(dev);
         usb_put_dev(dev);
         put_pid(ps->disc_pid);
+        put_cred(ps->cred);
 
         as = async_getcompleted(ps);
         while (as) {
@@ -1065,7 +1064,6 @@ static int proc_do_submiturb(struct dev_state *ps, struct usbdevfs_urb *uurb,
         struct usb_host_endpoint *ep;
         struct async *as;
         struct usb_ctrlrequest *dr = NULL;
-        const struct cred *cred = current_cred();
         unsigned int u, totlen, isofrmlen;
         int ret, ifnum = -1;
         int is_in;
@@ -1279,8 +1277,7 @@ static int proc_do_submiturb(struct dev_state *ps, struct usbdevfs_urb *uurb,
         as->signr = uurb->signr;
         as->ifnum = ifnum;
         as->pid = get_pid(task_pid(current));
-        as->uid = cred->uid;
-        as->euid = cred->euid;
+        as->cred = get_current_cred();
         security_task_getsecid(current, &as->secid);
         if (!is_in && uurb->buffer_length > 0) {
                 if (copy_from_user(as->urb->transfer_buffer, uurb->buffer,
@@ -1998,9 +1995,8 @@ static void usbdev_remove(struct usb_device *udev)
                         sinfo.si_errno = EPIPE;
                         sinfo.si_code = SI_ASYNCIO;
                         sinfo.si_addr = ps->disccontext;
-                        kill_pid_info_as_uid(ps->discsignr, &sinfo,
-                                        ps->disc_pid, ps->disc_uid,
-                                        ps->disc_euid, ps->secid);
+                        kill_pid_info_as_cred(ps->discsignr, &sinfo,
+                                        ps->disc_pid, ps->cred, ps->secid);
                 }
         }
 }
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 4ac2c0578e0f..57ddb5283d9f 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2166,7 +2166,8 @@ extern int force_sigsegv(int, struct task_struct *);
 extern int force_sig_info(int, struct siginfo *, struct task_struct *);
 extern int __kill_pgrp_info(int sig, struct siginfo *info, struct pid *pgrp);
 extern int kill_pid_info(int sig, struct siginfo *info, struct pid *pid);
-extern int kill_pid_info_as_uid(int, struct siginfo *, struct pid *, uid_t, uid_t, u32);
+extern int kill_pid_info_as_cred(int, struct siginfo *, struct pid *,
+                                const struct cred *, u32);
 extern int kill_pgrp(struct pid *pid, int sig, int priv);
 extern int kill_pid(struct pid *pid, int sig, int priv);
 extern int kill_proc_info(int, struct siginfo *, pid_t);
diff --git a/kernel/signal.c b/kernel/signal.c
index 291c9700be75..d252be2d3de5 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1344,13 +1344,24 @@ int kill_proc_info(int sig, struct siginfo *info, pid_t pid)
         return error;
 }
 
+static int kill_as_cred_perm(const struct cred *cred,
+                             struct task_struct *target)
+{
+        const struct cred *pcred = __task_cred(target);
+        if (cred->user_ns != pcred->user_ns)
+                return 0;
+        if (cred->euid != pcred->suid && cred->euid != pcred->uid &&
+            cred->uid  != pcred->suid && cred->uid  != pcred->uid)
+                return 0;
+        return 1;
+}
+
 /* like kill_pid_info(), but doesn't use uid/euid of "current" */
-int kill_pid_info_as_uid(int sig, struct siginfo *info, struct pid *pid,
-                      uid_t uid, uid_t euid, u32 secid)
+int kill_pid_info_as_cred(int sig, struct siginfo *info, struct pid *pid,
+                         const struct cred *cred, u32 secid)
 {
         int ret = -EINVAL;
         struct task_struct *p;
-        const struct cred *pcred;
         unsigned long flags;
 
         if (!valid_signal(sig))
@@ -1362,10 +1373,7 @@ int kill_pid_info_as_uid(int sig, struct siginfo *info, struct pid *pid,
                 ret = -ESRCH;
                 goto out_unlock;
         }
-        pcred = __task_cred(p);
-        if (si_fromuser(info) &&
-            euid != pcred->suid && euid != pcred->uid &&
-            uid  != pcred->suid && uid  != pcred->uid) {
+        if (si_fromuser(info) && !kill_as_cred_perm(cred, p)) {
                 ret = -EPERM;
                 goto out_unlock;
         }
@@ -1384,7 +1392,7 @@ out_unlock:
         rcu_read_unlock();
         return ret;
 }
-EXPORT_SYMBOL_GPL(kill_pid_info_as_uid);
+EXPORT_SYMBOL_GPL(kill_pid_info_as_cred);
 
 /*
  * kill_something_info() interprets pid in interesting ways just like kill(2).