diff options
Diffstat (limited to 'mm/usercopy.c')
| -rw-r--r-- | mm/usercopy.c | 170 |
1 files changed, 75 insertions, 95 deletions
diff --git a/mm/usercopy.c b/mm/usercopy.c index 14faadcedd06..5de7a518b1b1 100644 --- a/mm/usercopy.c +++ b/mm/usercopy.c @@ -1,3 +1,4 @@ +// SPDX-License-Identifier: GPL-2.0-only /* * This implements the various checks for CONFIG_HARDENED_USERCOPY*, * which are designed to protect kernel memory from needless exposure @@ -6,23 +7,22 @@ * * Copyright (C) 2001-2016 PaX Team, Bradley Spengler, Open Source * Security Inc. - * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License version 2 as - * published by the Free Software Foundation. - * */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include <linux/mm.h> +#include <linux/highmem.h> +#include <linux/kstrtox.h> #include <linux/slab.h> #include <linux/sched.h> #include <linux/sched/task.h> #include <linux/sched/task_stack.h> -#include <linux/thread_info.h> +#include <linux/ucopysize.h> +#include <linux/vmalloc.h> #include <linux/atomic.h> #include <linux/jump_label.h> #include <asm/sections.h> +#include "slab.h" /* * Checks if a given pointer and length is contained by the current @@ -31,7 +31,7 @@ * Returns: * NOT_STACK: not at all on the stack * GOOD_FRAME: fully within a valid stack frame - * GOOD_STACK: fully on the stack (when can't do frame-checking) + * GOOD_STACK: within the current stack (when can't frame-check exactly) * BAD_STACK: error condition (invalid stack position or bad stack frame) */ static noinline int check_stack_object(const void *obj, unsigned long len) @@ -46,7 +46,7 @@ static noinline int check_stack_object(const void *obj, unsigned long len) /* * Reject: object partially overlaps the stack (passing the - * the check above means at least one end is within the stack, + * check above means at least one end is within the stack, * so if this check fails, the other end is outside the stack). */ if (obj < stack || stackend < obj + len) @@ -57,6 +57,17 @@ static noinline int check_stack_object(const void *obj, unsigned long len) if (ret) return ret; + /* Finally, check stack depth if possible. */ +#ifdef CONFIG_ARCH_HAS_CURRENT_STACK_POINTER + if (IS_ENABLED(CONFIG_STACK_GROWSUP)) { + if ((void *)current_stack_pointer < obj + len) + return BAD_STACK; + } else { + if (obj < (void *)current_stack_pointer) + return BAD_STACK; + } +#endif + return GOOD_STACK; } @@ -72,17 +83,6 @@ static noinline int check_stack_object(const void *obj, unsigned long len) * kmem_cache_create_usercopy() function to create the cache (and * carefully audit the whitelist range). */ -void usercopy_warn(const char *name, const char *detail, bool to_user, - unsigned long offset, unsigned long len) -{ - WARN_ONCE(1, "Bad or missing usercopy whitelist? Kernel memory %s attempt detected %s %s%s%s%s (offset %lu, size %lu)!\n", - to_user ? "exposure" : "overwrite", - to_user ? "from" : "to", - name ? : "unknown?!", - detail ? " '" : "", detail ? : "", detail ? "'" : "", - offset, len); -} - void __noreturn usercopy_abort(const char *name, const char *detail, bool to_user, unsigned long offset, unsigned long len) @@ -151,7 +151,7 @@ static inline void check_bogus_address(const unsigned long ptr, unsigned long n, bool to_user) { /* Reject if object wraps past end of memory. */ - if (ptr + n < ptr) + if (ptr + (n - 1) < ptr) usercopy_abort("wrapped address", NULL, to_user, 0, ptr + n); /* Reject if NULL or ZERO-allocation. */ @@ -159,90 +159,59 @@ static inline void check_bogus_address(const unsigned long ptr, unsigned long n, usercopy_abort("null address", NULL, to_user, ptr, n); } -/* Checks for allocs that are marked in some way as spanning multiple pages. */ -static inline void check_page_span(const void *ptr, unsigned long n, - struct page *page, bool to_user) +static inline void check_heap_object(const void *ptr, unsigned long n, + bool to_user) { -#ifdef CONFIG_HARDENED_USERCOPY_PAGESPAN - const void *end = ptr + n - 1; - struct page *endpage; - bool is_reserved, is_cma; - - /* - * 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. - */ + unsigned long addr = (unsigned long)ptr; + unsigned long offset; + struct page *page; + struct slab *slab; - /* Allow reads of kernel rodata region (if not marked as Reserved). */ - if (ptr >= (const void *)__start_rodata && - end <= (const void *)__end_rodata) { - if (!to_user) - usercopy_abort("rodata", NULL, to_user, 0, n); + if (is_kmap_addr(ptr)) { + offset = offset_in_page(ptr); + if (n > PAGE_SIZE - offset) + usercopy_abort("kmap", NULL, to_user, offset, n); return; } - /* Allow kernel data region (if not marked as Reserved). */ - if (ptr >= (const void *)_sdata && end <= (const void *)_edata) - return; + if (is_vmalloc_addr(ptr) && !pagefault_disabled()) { + struct vmap_area *area = find_vmap_area(addr); - /* Allow kernel bss region (if not marked as Reserved). */ - if (ptr >= (const void *)__bss_start && - end <= (const void *)__bss_stop) - return; + if (!area) + usercopy_abort("vmalloc", "no area", to_user, 0, n); - /* Is the object wholly within one base page? */ - if (likely(((unsigned long)ptr & (unsigned long)PAGE_MASK) == - ((unsigned long)end & (unsigned long)PAGE_MASK))) + if (n > area->va_end - addr) { + offset = addr - area->va_start; + usercopy_abort("vmalloc", NULL, to_user, offset, n); + } return; - - /* Allow if fully inside the same compound (__GFP_COMP) page. */ - endpage = virt_to_head_page(end); - if (likely(endpage == page)) - return; - - /* - * Reject if range is entirely either Reserved (i.e. special or - * device memory), or CMA. Otherwise, reject since the object spans - * several independently allocated pages. - */ - is_reserved = PageReserved(page); - is_cma = is_migrate_cma_page(page); - if (!is_reserved && !is_cma) - usercopy_abort("spans multiple pages", NULL, to_user, 0, n); - - for (ptr += PAGE_SIZE; ptr <= end; ptr += PAGE_SIZE) { - page = virt_to_head_page(ptr); - if (is_reserved && !PageReserved(page)) - usercopy_abort("spans Reserved and non-Reserved pages", - NULL, to_user, 0, n); - if (is_cma && !is_migrate_cma_page(page)) - usercopy_abort("spans CMA and non-CMA pages", NULL, - to_user, 0, n); } -#endif -} - -static inline void check_heap_object(const void *ptr, unsigned long n, - bool to_user) -{ - struct page *page; if (!virt_addr_valid(ptr)) return; - page = virt_to_head_page(ptr); - - if (PageSlab(page)) { + page = virt_to_page(ptr); + slab = page_slab(page); + if (slab) { /* Check slab allocator for flags and size. */ - __check_heap_object(ptr, n, page, to_user); - } else { - /* Verify object does not incorrectly span multiple pages. */ - check_page_span(ptr, n, page, to_user); + __check_heap_object(ptr, n, slab, to_user); + } else if (PageCompound(page)) { + page = compound_head(page); + offset = ptr - page_address(page); + if (n > page_size(page) - offset) + usercopy_abort("page alloc", NULL, to_user, offset, n); } + + /* + * We cannot check non-compound pages. They might be part of + * a large allocation, in which case crossing a page boundary + * is fine. + */ } -static DEFINE_STATIC_KEY_FALSE_RO(bypass_usercopy_checks); +DEFINE_STATIC_KEY_MAYBE_RO(CONFIG_HARDENED_USERCOPY_DEFAULT_ON, + validate_usercopy_range); +EXPORT_SYMBOL(validate_usercopy_range); /* * Validates that the given object is: @@ -253,9 +222,6 @@ static DEFINE_STATIC_KEY_FALSE_RO(bypass_usercopy_checks); */ void __check_object_size(const void *ptr, unsigned long n, bool to_user) { - if (static_branch_unlikely(&bypass_usercopy_checks)) - return; - /* Skip all tests if size is zero. */ if (!n) return; @@ -277,7 +243,15 @@ void __check_object_size(const void *ptr, unsigned long n, bool to_user) */ return; default: - usercopy_abort("process stack", NULL, to_user, 0, n); + usercopy_abort("process stack", NULL, to_user, +#ifdef CONFIG_ARCH_HAS_CURRENT_STACK_POINTER + IS_ENABLED(CONFIG_STACK_GROWSUP) ? + ptr - (void *)current_stack_pointer : + (void *)current_stack_pointer - ptr, +#else + 0, +#endif + n); } /* Check for bad heap object. */ @@ -288,19 +262,25 @@ void __check_object_size(const void *ptr, unsigned long n, bool to_user) } EXPORT_SYMBOL(__check_object_size); -static bool enable_checks __initdata = true; +static bool enable_checks __initdata = + IS_ENABLED(CONFIG_HARDENED_USERCOPY_DEFAULT_ON); static int __init parse_hardened_usercopy(char *str) { - return strtobool(str, &enable_checks); + if (kstrtobool(str, &enable_checks)) + pr_warn("Invalid option string for hardened_usercopy: '%s'\n", + str); + return 1; } __setup("hardened_usercopy=", parse_hardened_usercopy); static int __init set_hardened_usercopy(void) { - if (enable_checks == false) - static_branch_enable(&bypass_usercopy_checks); + if (enable_checks) + static_branch_enable(&validate_usercopy_range); + else + static_branch_disable(&validate_usercopy_range); return 1; } |