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[PATCH] slab: don't BUG on duplicated cache

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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: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Andrew Morton 2005-11-07 00:58:00 -08:00 committed by Linus Torvalds
parent 7fd93cf30c
commit 4f12bb4f77
1 changed files with 34 additions and 33 deletions
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67
mm/slab.c
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@ -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);