Commit 53944f17 authored by Stephen Kitt's avatar Stephen Kitt Committed by Linus Torvalds
Browse files

mm: remove HARDENED_USERCOPY_FALLBACK 

This has served its purpose and is no longer used.  All usercopy
violations appear to have been handled by now, any remaining instances
(or new bugs) will cause copies to be rejected.

This isn't a direct revert of commit 2d891fbc ("usercopy: Allow
strict enforcement of whitelists"); since usercopy_fallback is
effectively 0, the fallback handling is removed too.

This also removes the usercopy_fallback module parameter on slab_common.

Link: https://github.com/KSPP/linux/issues/153
Link: https://lkml.kernel.org/r/20210921061149.1091163-1-steve@sk2.org


Signed-off-by: default avatarStephen Kitt <steve@sk2.org>
Suggested-by: default avatarKees Cook <keescook@chromium.org>
Acked-by: default avatarKees Cook <keescook@chromium.org>
Reviewed-by: Joel Stanley <joel@jms.id.au>	[defconfig change]
Acked-by: default avatarDavid Rientjes <rientjes@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: James Morris <jmorris@namei.org>
Cc: "Serge E . Hallyn" <serge@hallyn.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 755804d1

arch/powerpc/configs/skiroot_defconfig

+0 −1
Original line number Diff line number Diff line
@@ -275,7 +275,6 @@ CONFIG_NLS_UTF8=y 
CONFIG_ENCRYPTED_KEYS=y

CONFIG_SECURITY=y

CONFIG_HARDENED_USERCOPY=y

# CONFIG_HARDENED_USERCOPY_FALLBACK is not set

CONFIG_HARDENED_USERCOPY_PAGESPAN=y

CONFIG_FORTIFY_SOURCE=y

CONFIG_SECURITY_LOCKDOWN_LSM=y

include/linux/slab.h

+0 −2
Original line number Diff line number Diff line
@@ -142,8 +142,6 @@ struct mem_cgroup; 
void __init kmem_cache_init(void);

bool slab_is_available(void);



extern bool usercopy_fallback;



struct kmem_cache *kmem_cache_create(const char *name, unsigned int size,

			unsigned int align, slab_flags_t flags,

			void (*ctor)(void *));

mm/slab.c

+0 −13
Original line number Diff line number Diff line
@@ -4204,19 +4204,6 @@ void __check_heap_object(const void *ptr, unsigned long n, struct page *page, 
	    n <= cachep->useroffset - offset + cachep->usersize)

		return;



	/*

	 * If the copy is still within the allocated object, produce

	 * a warning instead of rejecting the copy. This is intended

	 * to be a temporary method to find any missing usercopy

	 * whitelists.

	 */

	if (usercopy_fallback &&

	    offset <= cachep->object_size &&

	    n <= cachep->object_size - offset) {

		usercopy_warn("SLAB object", cachep->name, to_user, offset, n);

		return;

	}



	usercopy_abort("SLAB object", cachep->name, to_user, offset, n);

}

#endif /* CONFIG_HARDENED_USERCOPY */

mm/slab_common.c

+0 −8
Original line number Diff line number Diff line
@@ -37,14 +37,6 @@ LIST_HEAD(slab_caches); 
DEFINE_MUTEX(slab_mutex);

struct kmem_cache *kmem_cache;



#ifdef CONFIG_HARDENED_USERCOPY

bool usercopy_fallback __ro_after_init =

		IS_ENABLED(CONFIG_HARDENED_USERCOPY_FALLBACK);

module_param(usercopy_fallback, bool, 0400);

MODULE_PARM_DESC(usercopy_fallback,

		"WARN instead of reject usercopy whitelist violations");

#endif



static LIST_HEAD(slab_caches_to_rcu_destroy);

static void slab_caches_to_rcu_destroy_workfn(struct work_struct *work);

static DECLARE_WORK(slab_caches_to_rcu_destroy_work,

mm/slub.c

+0 −14
Original line number Diff line number Diff line
@@ -4489,7 +4489,6 @@ void __check_heap_object(const void *ptr, unsigned long n, struct page *page, 
{

	struct kmem_cache *s;

	unsigned int offset;

	size_t object_size;

	bool is_kfence = is_kfence_address(ptr);



	ptr = kasan_reset_tag(ptr);
@@ -4522,19 +4521,6 @@ void __check_heap_object(const void *ptr, unsigned long n, struct page *page, 
	    n <= s->useroffset - offset + s->usersize)

		return;



	/*

	 * If the copy is still within the allocated object, produce

	 * a warning instead of rejecting the copy. This is intended

	 * to be a temporary method to find any missing usercopy

	 * whitelists.

	 */

	object_size = slab_ksize(s);

	if (usercopy_fallback &&

	    offset <= object_size && n <= object_size - offset) {

		usercopy_warn("SLUB object", s->name, to_user, offset, n);

		return;

	}



	usercopy_abort("SLUB object", s->name, to_user, offset, n);

}

#endif /* CONFIG_HARDENED_USERCOPY */