Commit 4f12bb4f authored by Andrew Morton's avatar Andrew Morton Committed by Linus Torvalds
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[PATCH] slab: don't BUG on duplicated cache 



slab presently goes BUG if someone tries to register an already-registered
cache.

But this can happen if the user accidentally loads a module which is already
statically linked into the kernel.  Nuking the kernel is rather a harsh
reaction.

Change it into a warning, and just fail the kmem_cache_alloc() attempt.  If
the module is well-behaved, the modprobe will fail and all is well.

Notes:

- Swaps the ranking of cache_chain_sem and lock_cpu_hotplug().  Doesn't seem
  important.

Acked-by: default avatarManfred Spraul <manfred@colorfullife.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 7fd93cf3

mm/slab.c

+34 −33
Original line number Diff line number Diff line
@@ -1502,6 +1502,7 @@ kmem_cache_create (const char *name, size_t size, size_t align, 
{

	size_t left_over, slab_size, ralign;

	kmem_cache_t *cachep = NULL;

	struct list_head *p;



	/*

	 * Sanity checks... these are all serious usage bugs.
@@ -1516,6 +1517,35 @@ kmem_cache_create (const char *name, size_t size, size_t align, 
			BUG();

		}



	down(&cache_chain_sem);



	list_for_each(p, &cache_chain) {

		kmem_cache_t *pc = list_entry(p, kmem_cache_t, next);

		mm_segment_t old_fs = get_fs();

		char tmp;

		int res;



		/*

		 * This happens when the module gets unloaded and doesn't

		 * destroy its slab cache and no-one else reuses the vmalloc

		 * area of the module.  Print a warning.

		 */

		set_fs(KERNEL_DS);

		res = __get_user(tmp, pc->name);

		set_fs(old_fs);

		if (res) {

			printk("SLAB: cache with size %d has lost its name\n",

					pc->objsize);

			continue;

		}



		if (!strcmp(pc->name,name)) {

			printk("kmem_cache_create: duplicate cache %s\n", name);

			dump_stack();

			goto oops;

		}

	}



#if DEBUG

	WARN_ON(strchr(name, ' '));	/* It confuses parsers */

	if ((flags & SLAB_DEBUG_INITIAL) && !ctor) {
@@ -1592,7 +1622,7 @@ kmem_cache_create (const char *name, size_t size, size_t align, 
	/* Get cache's description obj. */

	cachep = (kmem_cache_t *) kmem_cache_alloc(&cache_cache, SLAB_KERNEL);

	if (!cachep)

		goto opps;

		goto oops;

	memset(cachep, 0, sizeof(kmem_cache_t));



#if DEBUG
@@ -1686,7 +1716,7 @@ next: 
		printk("kmem_cache_create: couldn't create cache %s.\n", name);

		kmem_cache_free(&cache_cache, cachep);

		cachep = NULL;

		goto opps;

		goto oops;

	}

	slab_size = ALIGN(cachep->num*sizeof(kmem_bufctl_t)

				+ sizeof(struct slab), align);
@@ -1781,43 +1811,14 @@ next: 
		cachep->limit = BOOT_CPUCACHE_ENTRIES;

	} 



	/* Need the semaphore to access the chain. */

	down(&cache_chain_sem);

	{

		struct list_head *p;

		mm_segment_t old_fs;



		old_fs = get_fs();

		set_fs(KERNEL_DS);

		list_for_each(p, &cache_chain) {

			kmem_cache_t *pc = list_entry(p, kmem_cache_t, next);

			char tmp;

			/* This happens when the module gets unloaded and doesn't

			   destroy its slab cache and noone else reuses the vmalloc

			   area of the module. Print a warning. */

			if (__get_user(tmp,pc->name)) { 

				printk("SLAB: cache with size %d has lost its name\n", 

					pc->objsize); 

				continue; 

			} 	

			if (!strcmp(pc->name,name)) { 

				printk("kmem_cache_create: duplicate cache %s\n",name); 

				up(&cache_chain_sem); 

				unlock_cpu_hotplug();

				BUG(); 

			}	

		}

		set_fs(old_fs);

	}



	/* cache setup completed, link it into the list */

	list_add(&cachep->next, &cache_chain);

	up(&cache_chain_sem);

	unlock_cpu_hotplug();

opps:

oops:

	if (!cachep && (flags & SLAB_PANIC))

		panic("kmem_cache_create(): failed to create slab `%s'\n",

			name);

	up(&cache_chain_sem);

	return cachep;

}

EXPORT_SYMBOL(kmem_cache_create);

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