diff options
| -rw-r--r-- | include/linux/thread_info.h | 4 | ||||
| -rw-r--r-- | mm/usercopy.c | 61 | ||||
| -rw-r--r-- | security/Kconfig | 11 |
3 files changed, 48 insertions, 28 deletions
diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h index 10c9e60..2b5b10e 100644 --- a/include/linux/thread_info.h +++ b/include/linux/thread_info.h @@ -118,8 +118,8 @@ static inline int arch_within_stack_frames(const void * const stack, extern void __check_object_size(const void *ptr, unsigned long n, bool to_user); -static inline void check_object_size(const void *ptr, unsigned long n, - bool to_user) +static __always_inline void check_object_size(const void *ptr, unsigned long n, + bool to_user) { if (!__builtin_constant_p(n)) __check_object_size(ptr, n, to_user); diff --git a/mm/usercopy.c b/mm/usercopy.c index a3cc305..089328f 100644 --- a/mm/usercopy.c +++ b/mm/usercopy.c @@ -134,31 +134,16 @@ static inline const char *check_bogus_address(const void *ptr, unsigned long n) return NULL; } -static inline const char *check_heap_object(const void *ptr, unsigned long n, - bool to_user) +/* Checks for allocs that are marked in some way as spanning multiple pages. */ +static inline const char *check_page_span(const void *ptr, unsigned long n, + struct page *page, bool to_user) { - struct page *page, *endpage; +#ifdef CONFIG_HARDENED_USERCOPY_PAGESPAN const void *end = ptr + n - 1; + struct page *endpage; bool is_reserved, is_cma; /* - * Some architectures (arm64) return true for virt_addr_valid() on - * vmalloced addresses. Work around this by checking for vmalloc - * first. - */ - if (is_vmalloc_addr(ptr)) - return NULL; - - if (!virt_addr_valid(ptr)) - return NULL; - - page = virt_to_head_page(ptr); - - /* Check slab allocator for flags and size. */ - if (PageSlab(page)) - return __check_heap_object(ptr, n, page); - - /* * Sometimes the kernel data regions are not marked Reserved (see * check below). And sometimes [_sdata,_edata) does not cover * rodata and/or bss, so check each range explicitly. @@ -186,7 +171,7 @@ static inline const char *check_heap_object(const void *ptr, unsigned long n, ((unsigned long)end & (unsigned long)PAGE_MASK))) return NULL; - /* Allow if start and end are inside the same compound page. */ + /* Allow if fully inside the same compound (__GFP_COMP) page. */ endpage = virt_to_head_page(end); if (likely(endpage == page)) return NULL; @@ -199,20 +184,44 @@ static inline const char *check_heap_object(const void *ptr, unsigned long n, is_reserved = PageReserved(page); is_cma = is_migrate_cma_page(page); if (!is_reserved && !is_cma) - goto reject; + return "<spans multiple pages>"; for (ptr += PAGE_SIZE; ptr <= end; ptr += PAGE_SIZE) { page = virt_to_head_page(ptr); if (is_reserved && !PageReserved(page)) - goto reject; + return "<spans Reserved and non-Reserved pages>"; if (is_cma && !is_migrate_cma_page(page)) - goto reject; + return "<spans CMA and non-CMA pages>"; } +#endif return NULL; +} + +static inline const char *check_heap_object(const void *ptr, unsigned long n, + bool to_user) +{ + struct page *page; + + /* + * Some architectures (arm64) return true for virt_addr_valid() on + * vmalloced addresses. Work around this by checking for vmalloc + * first. + */ + if (is_vmalloc_addr(ptr)) + return NULL; + + if (!virt_addr_valid(ptr)) + return NULL; + + page = virt_to_head_page(ptr); + + /* Check slab allocator for flags and size. */ + if (PageSlab(page)) + return __check_heap_object(ptr, n, page); -reject: - return "<spans multiple pages>"; + /* Verify object does not incorrectly span multiple pages. */ + return check_page_span(ptr, n, page, to_user); } /* diff --git a/security/Kconfig b/security/Kconfig index da10d9b..118f454 100644 --- a/security/Kconfig +++ b/security/Kconfig @@ -147,6 +147,17 @@ config HARDENED_USERCOPY or are part of the kernel text. This kills entire classes of heap overflow exploits and similar kernel memory exposures. +config HARDENED_USERCOPY_PAGESPAN + bool "Refuse to copy allocations that span multiple pages" + depends on HARDENED_USERCOPY + depends on EXPERT + help + When a multi-page allocation is done without __GFP_COMP, + hardened usercopy will reject attempts to copy it. There are, + however, several cases of this in the kernel that have not all + been removed. This config is intended to be used only while + trying to find such users. + source security/selinux/Kconfig source security/smack/Kconfig source security/tomoyo/Kconfig |
