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Date: Mon, 10 Jan 2022 23:15:29 +0000 From: "Matthew Wilcox (Oracle)" <willy@...radead.org> To: Kees Cook <keescook@...omium.org> Cc: "Matthew Wilcox (Oracle)" <willy@...radead.org>, linux-mm@...ck.org, linux-hardening@...r.kernel.org Subject: [PATCH 3/4] mm/usercopy: Detect large folio overruns Move the compound page overrun detection out of CONFIG_HARDENED_USERCOPY_PAGESPAN and convert it to use folios so it's enabled for more people. Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org> Acked-by: Kees Cook <keescook@...omium.org> --- mm/usercopy.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) diff --git a/mm/usercopy.c b/mm/usercopy.c index dcf71b7e3098..e1cb98087a05 100644 --- a/mm/usercopy.c +++ b/mm/usercopy.c @@ -164,7 +164,6 @@ static inline void check_page_span(const void *ptr, unsigned long n, { #ifdef CONFIG_HARDENED_USERCOPY_PAGESPAN const void *end = ptr + n - 1; - struct page *endpage; bool is_reserved, is_cma; /* @@ -195,11 +194,6 @@ static inline void check_page_span(const void *ptr, unsigned long n, ((unsigned long)end & (unsigned long)PAGE_MASK))) 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 @@ -259,6 +253,10 @@ static inline void check_heap_object(const void *ptr, unsigned long n, if (folio_test_slab(folio)) { /* Check slab allocator for flags and size. */ __check_heap_object(ptr, n, folio_slab(folio), to_user); + } else if (folio_test_large(folio)) { + unsigned long offset = ptr - folio_address(folio); + if (offset + n > folio_size(folio)) + usercopy_abort("page alloc", NULL, to_user, offset, n); } else { /* Verify object does not incorrectly span multiple pages. */ check_page_span(ptr, n, folio_page(folio, 0), to_user); -- 2.33.0
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