[PATCH] uml: prevent umid theft

Behavior when booting two UMLs with the same umid was broken.  The second one
would steal the umid.  This fixes that, making the second UML take a random
umid instead.

Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/arch/um/os-Linux/umid.c b/arch/um/os-Linux/umid.c
index ecf107ae5ac87704afc39021c9c178b6fc641547..198e591632887ce4b7abc0c9a39cfbd3b41c25c4 100644 (file)
--- a/arch/um/os-Linux/umid.c
+++ b/arch/um/os-Linux/umid.c
@@ -143,8 +143,10 @@ static int not_dead_yet(char *dir)
                goto out_close;
        }
 
-       if((kill(p, 0) == 0) || (errno != ESRCH))
+       if((kill(p, 0) == 0) || (errno != ESRCH)){
+               printk("umid \"%s\" is already in use by pid %d\n", umid, p);
                return 1;
+       }
 
        err = actually_do_remove(dir);
        if(err)
@@ -234,33 +236,44 @@ int __init make_umid(void)
        err = mkdir(tmp, 0777);
        if(err < 0){
                err = -errno;
-               if(errno != EEXIST)
+               if(err != -EEXIST)
                        goto err;
 
-               if(not_dead_yet(tmp) < 0)
+               /* 1   -> this umid is already in use
+                * < 0 -> we couldn't remove the umid directory
+                * In either case, we can't use this umid, so return -EEXIST.
+                */
+               if(not_dead_yet(tmp) != 0)
                        goto err;
 
                err = mkdir(tmp, 0777);
        }
-       if(err < 0){
-               printk("Failed to create '%s' - err = %d\n", umid, err);
-               goto err_rmdir;
+       if(err){
+               err = -errno;
+               printk("Failed to create '%s' - err = %d\n", umid, -errno);
+               goto err;
        }
 
        umid_setup = 1;
 
        create_pid_file();
 
-       return 0;
-
- err_rmdir:
-       rmdir(tmp);
+       err = 0;
  err:
        return err;
 }
 
 static int __init make_umid_init(void)
 {
+       if(!make_umid())
+               return 0;
+
+       /* If initializing with the given umid failed, then try again with
+        * a random one.
+        */
+       printk("Failed to initialize umid \"%s\", trying with a random umid\n",
+              umid);
+       *umid = '\0';
        make_umid();
 
        return 0;