[PATCH] random: remove pool resizing sysctl

Remove random pool resizing sysctl.  It's racy in hard to fix ways and
doesn't really warrant fixing.  It also only allows adjusting the input
pool size so it's either obsolete or incomplete.

The default 4kbits (512 bytes) of entropy pool should be more than big
enough for all purposes and too small to be a memory concern.

This patch removes the resizing code and marks the sysctl read-only.
Signed-off-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/char/random.c

@@ -170,9 +170,7 @@
  *		touch $random_seed
  *	fi
  *	chmod 600 $random_seed
- *	poolfile=/proc/sys/kernel/random/poolsize
- *	[ -r $poolfile ] && bytes=`cat $poolfile` || bytes=512
- *	dd if=/dev/urandom of=$random_seed count=1 bs=$bytes
+ *	dd if=/dev/urandom of=$random_seed count=1 bs=512
  *
  * and the following lines in an appropriate script which is run as
  * the system is shutdown:
@@ -183,9 +181,7 @@
  *	random_seed=/var/run/random-seed
  *	touch $random_seed
  *	chmod 600 $random_seed
- *	poolfile=/proc/sys/kernel/random/poolsize
- *	[ -r $poolfile ] && bytes=`cat $poolfile` || bytes=512
- *	dd if=/dev/urandom of=$random_seed count=1 bs=$bytes
+ *	dd if=/dev/urandom of=$random_seed count=1 bs=512
  *
  * For example, on most modern systems using the System V init
  * scripts, such code fragments would be found in
@@ -554,14 +550,6 @@ static void clear_entropy_store(struct entropy_store *r)
 	memset(r->pool, 0, r->poolinfo.POOLBYTES);
 }
 
-#ifdef CONFIG_SYSCTL
-static void free_entropy_store(struct entropy_store *r)
-{
-	if (r->pool)
-		kfree(r->pool);
-	kfree(r);
-}
-#endif
 /*
  * This function adds a byte into the entropy "pool".  It does not
  * update the entropy estimate.  The caller should call
@@ -1853,77 +1841,10 @@ EXPORT_SYMBOL(generate_random_uuid);
 
 #include <linux/sysctl.h>
 
-static int sysctl_poolsize;
 static int min_read_thresh, max_read_thresh;
 static int min_write_thresh, max_write_thresh;
 static char sysctl_bootid[16];
 
-/*
- * This function handles a request from the user to change the pool size
- * of the primary entropy store.
- */
-static int change_poolsize(int poolsize)
-{
-	struct entropy_store *new_store, *old_store;
-	int ret;
-
-	if ((ret = create_entropy_store(poolsize, random_state->name,
-					&new_store)))
-		return ret;
-
-	add_entropy_words(new_store, random_state->pool,
-			  random_state->poolinfo.poolwords);
-	credit_entropy_store(new_store, random_state->entropy_count);
-
-	sysctl_init_random(new_store);
-	old_store = random_state;
-	random_state = batch_work.data = new_store;
-	free_entropy_store(old_store);
-	return 0;
-}
-
-static int proc_do_poolsize(ctl_table *table, int write, struct file *filp,
-			    void __user *buffer, size_t *lenp, loff_t *ppos)
-{
-	int ret;
-
-	sysctl_poolsize = random_state->poolinfo.POOLBYTES;
-
-	ret = proc_dointvec(table, write, filp, buffer, lenp, ppos);
-	if (ret || !write ||
-	    (sysctl_poolsize == random_state->poolinfo.POOLBYTES))
-		return ret;
-
-	return change_poolsize(sysctl_poolsize);
-}
-
-static int poolsize_strategy(ctl_table *table, int __user *name, int nlen,
-			     void __user *oldval, size_t __user *oldlenp,
-			     void __user *newval, size_t newlen, void **context)
-{
-	int len;
-
-	sysctl_poolsize = random_state->poolinfo.POOLBYTES;
-
-	/*
-	 * We only handle the write case, since the read case gets
-	 * handled by the default handler (and we don't care if the
-	 * write case happens twice; it's harmless).
-	 */
-	if (newval && newlen) {
-		len = newlen;
-		if (len > table->maxlen)
-			len = table->maxlen;
-		if (copy_from_user(table->data, newval, len))
-			return -EFAULT;
-	}
-
-	if (sysctl_poolsize != random_state->poolinfo.POOLBYTES)
-		return change_poolsize(sysctl_poolsize);
-
-	return 0;
-}
-
 /*
  * These functions is used to return both the bootid UUID, and random
  * UUID.  The difference is in whether table->data is NULL; if it is,
@@ -1989,15 +1910,15 @@ static int uuid_strategy(ctl_table *table, int __user *name, int nlen,
 	return 1;
 }
 
+static int sysctl_poolsize = DEFAULT_POOL_SIZE;
 ctl_table random_table[] = {
 	{
 		.ctl_name 	= RANDOM_POOLSIZE,
 		.procname	= "poolsize",
 		.data		= &sysctl_poolsize,
 		.maxlen		= sizeof(int),
-		.mode		= 0644,
-		.proc_handler	= &proc_do_poolsize,
-		.strategy	= &poolsize_strategy,
+		.mode		= 0444,
+		.proc_handler	= &proc_dointvec,
 	},
 	{
 		.ctl_name	= RANDOM_ENTROPY_COUNT,