[PATCH v3 11/11] mm: SLUB hardened usercopy support
From: Kees Cook <hidden>
Date: 2016-07-15 21:46:48
Also in:
linux-arm-kernel, linux-mm, linuxppc-dev, lkml, sparclinux
Subsystem:
memory management, slab allocator, the rest · Maintainers:
Andrew Morton, Vlastimil Babka, Harry Yoo, Linus Torvalds
Under CONFIG_HARDENED_USERCOPY, this adds object size checking to the SLUB allocator to catch any copies that may span objects. Includes a redzone handling fix discovered by Michael Ellerman. Based on code from PaX and grsecurity. Signed-off-by: Kees Cook <redacted> Tested-by: Michael Ellerman <mpe@ellerman.id.au> --- init/Kconfig | 1 + mm/slub.c | 36 ++++++++++++++++++++++++++++++++++++ 2 files changed, 37 insertions(+)
diff --git a/init/Kconfig b/init/Kconfig
index 798c2020ee7c..1c4711819dfd 100644
--- a/init/Kconfig
+++ b/init/Kconfig@@ -1765,6 +1765,7 @@ config SLAB config SLUB bool "SLUB (Unqueued Allocator)" + select HAVE_HARDENED_USERCOPY_ALLOCATOR help SLUB is a slab allocator that minimizes cache line usage instead of managing queues of cached objects (SLAB approach).
diff --git a/mm/slub.c b/mm/slub.c
index 825ff4505336..7dee3d9a5843 100644
--- a/mm/slub.c
+++ b/mm/slub.c@@ -3614,6 +3614,42 @@ void *__kmalloc_node(size_t size, gfp_t flags, int node) EXPORT_SYMBOL(__kmalloc_node); #endif +#ifdef CONFIG_HARDENED_USERCOPY +/* + * Rejects objects that are incorrectly sized. + * + * Returns NULL if check passes, otherwise const char * to name of cache + * to indicate an error. + */ +const char *__check_heap_object(const void *ptr, unsigned long n, + struct page *page) +{ + struct kmem_cache *s; + unsigned long offset; + size_t object_size; + + /* Find object and usable object size. */ + s = page->slab_cache; + object_size = slab_ksize(s); + + /* Find offset within object. */ + offset = (ptr - page_address(page)) % s->size; + + /* Adjust for redzone and reject if within the redzone. */ + if (kmem_cache_debug(s) && s->flags & SLAB_RED_ZONE) { + if (offset < s->red_left_pad) + return s->name; + offset -= s->red_left_pad; + } + + /* Allow address range falling entirely within object size. */ + if (offset <= object_size && n <= object_size - offset) + return NULL; + + return s->name; +} +#endif /* CONFIG_HARDENED_USERCOPY */ + static size_t __ksize(const void *object) { struct page *page;
--
2.7.4