diff options
Diffstat (limited to 'mm/usercopy.c')
| -rw-r--r-- | mm/usercopy.c | 133 |
1 files changed, 74 insertions, 59 deletions
diff --git a/mm/usercopy.c b/mm/usercopy.c index a9852b24715d..e9e9325f7638 100644 --- a/mm/usercopy.c +++ b/mm/usercopy.c @@ -58,12 +58,40 @@ static noinline int check_stack_object(const void *obj, unsigned long len) return GOOD_STACK; } -static void report_usercopy(const void *ptr, unsigned long len, - bool to_user, const char *type) +/* + * If these functions are reached, then CONFIG_HARDENED_USERCOPY has found + * an unexpected state during a copy_from_user() or copy_to_user() call. + * There are several checks being performed on the buffer by the + * __check_object_size() function. Normal stack buffer usage should never + * trip the checks, and kernel text addressing will always trip the check. + * For cache objects, it is checking that only the whitelisted range of + * bytes for a given cache is being accessed (via the cache's usersize and + * useroffset fields). To adjust a cache whitelist, use the usercopy-aware + * 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) { - pr_emerg("kernel memory %s attempt detected %s %p (%s) (%lu bytes)\n", - to_user ? "exposure" : "overwrite", - to_user ? "from" : "to", ptr, type ? : "unknown", len); + pr_emerg("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); + /* * For greater effect, it would be nice to do do_group_exit(), * but BUG() actually hooks all the lock-breaking and per-arch @@ -73,10 +101,10 @@ static void report_usercopy(const void *ptr, unsigned long len, } /* Returns true if any portion of [ptr,ptr+n) over laps with [low,high). */ -static bool overlaps(const void *ptr, unsigned long n, unsigned long low, - unsigned long high) +static bool overlaps(const unsigned long ptr, unsigned long n, + unsigned long low, unsigned long high) { - unsigned long check_low = (uintptr_t)ptr; + const unsigned long check_low = ptr; unsigned long check_high = check_low + n; /* Does not overlap if entirely above or entirely below. */ @@ -87,15 +115,15 @@ static bool overlaps(const void *ptr, unsigned long n, unsigned long low, } /* Is this address range in the kernel text area? */ -static inline const char *check_kernel_text_object(const void *ptr, - unsigned long n) +static inline void check_kernel_text_object(const unsigned long ptr, + unsigned long n, bool to_user) { unsigned long textlow = (unsigned long)_stext; unsigned long texthigh = (unsigned long)_etext; unsigned long textlow_linear, texthigh_linear; if (overlaps(ptr, n, textlow, texthigh)) - return "<kernel text>"; + usercopy_abort("kernel text", NULL, to_user, ptr - textlow, n); /* * Some architectures have virtual memory mappings with a secondary @@ -108,32 +136,30 @@ static inline const char *check_kernel_text_object(const void *ptr, textlow_linear = (unsigned long)lm_alias(textlow); /* No different mapping: we're done. */ if (textlow_linear == textlow) - return NULL; + return; /* Check the secondary mapping... */ texthigh_linear = (unsigned long)lm_alias(texthigh); if (overlaps(ptr, n, textlow_linear, texthigh_linear)) - return "<linear kernel text>"; - - return NULL; + usercopy_abort("linear kernel text", NULL, to_user, + ptr - textlow_linear, n); } -static inline const char *check_bogus_address(const void *ptr, unsigned long n) +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 ((unsigned long)ptr + n < (unsigned long)ptr) - return "<wrapped address>"; + if (ptr + n < ptr) + usercopy_abort("wrapped address", NULL, to_user, 0, ptr + n); /* Reject if NULL or ZERO-allocation. */ if (ZERO_OR_NULL_PTR(ptr)) - return "<null>"; - - return NULL; + usercopy_abort("null address", NULL, to_user, ptr, n); } /* 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) +static inline void check_page_span(const void *ptr, unsigned long n, + struct page *page, bool to_user) { #ifdef CONFIG_HARDENED_USERCOPY_PAGESPAN const void *end = ptr + n - 1; @@ -150,28 +176,28 @@ static inline const char *check_page_span(const void *ptr, unsigned long n, if (ptr >= (const void *)__start_rodata && end <= (const void *)__end_rodata) { if (!to_user) - return "<rodata>"; - return NULL; + usercopy_abort("rodata", NULL, to_user, 0, n); + return; } /* Allow kernel data region (if not marked as Reserved). */ if (ptr >= (const void *)_sdata && end <= (const void *)_edata) - return NULL; + return; /* Allow kernel bss region (if not marked as Reserved). */ if (ptr >= (const void *)__bss_start && end <= (const void *)__bss_stop) - return NULL; + return; /* Is the object wholly within one base page? */ if (likely(((unsigned long)ptr & (unsigned long)PAGE_MASK) == ((unsigned long)end & (unsigned long)PAGE_MASK))) - return NULL; + return; /* Allow if fully inside the same compound (__GFP_COMP) page. */ endpage = virt_to_head_page(end); if (likely(endpage == page)) - return NULL; + return; /* * Reject if range is entirely either Reserved (i.e. special or @@ -181,36 +207,37 @@ static inline const char *check_page_span(const void *ptr, unsigned long n, is_reserved = PageReserved(page); is_cma = is_migrate_cma_page(page); if (!is_reserved && !is_cma) - return "<spans multiple pages>"; + 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)) - return "<spans Reserved and non-Reserved pages>"; + usercopy_abort("spans Reserved and non-Reserved pages", + NULL, to_user, 0, n); if (is_cma && !is_migrate_cma_page(page)) - return "<spans CMA and non-CMA pages>"; + usercopy_abort("spans CMA and non-CMA pages", NULL, + to_user, 0, n); } #endif - - return NULL; } -static inline const char *check_heap_object(const void *ptr, unsigned long n, - bool to_user) +static inline void check_heap_object(const void *ptr, unsigned long n, + bool to_user) { struct page *page; if (!virt_addr_valid(ptr)) - return NULL; + return; page = virt_to_head_page(ptr); - /* Check slab allocator for flags and size. */ - if (PageSlab(page)) - return __check_heap_object(ptr, n, page); - - /* Verify object does not incorrectly span multiple pages. */ - return check_page_span(ptr, n, page, to_user); + if (PageSlab(page)) { + /* 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); + } } /* @@ -221,21 +248,15 @@ static inline const char *check_heap_object(const void *ptr, unsigned long n, */ void __check_object_size(const void *ptr, unsigned long n, bool to_user) { - const char *err; - /* Skip all tests if size is zero. */ if (!n) return; /* Check for invalid addresses. */ - err = check_bogus_address(ptr, n); - if (err) - goto report; + check_bogus_address((const unsigned long)ptr, n, to_user); /* Check for bad heap object. */ - err = check_heap_object(ptr, n, to_user); - if (err) - goto report; + check_heap_object(ptr, n, to_user); /* Check for bad stack object. */ switch (check_stack_object(ptr, n)) { @@ -251,16 +272,10 @@ void __check_object_size(const void *ptr, unsigned long n, bool to_user) */ return; default: - err = "<process stack>"; - goto report; + usercopy_abort("process stack", NULL, to_user, 0, n); } /* Check for object in kernel to avoid text exposure. */ - err = check_kernel_text_object(ptr, n); - if (!err) - return; - -report: - report_usercopy(ptr, n, to_user, err); + check_kernel_text_object((const unsigned long)ptr, n, to_user); } EXPORT_SYMBOL(__check_object_size); |