Commit ab502103 authored by Matthew Wilcox (Oracle)'s avatar Matthew Wilcox (Oracle) Committed by Kees Cook
Browse files

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: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: default avatarKees Cook <keescook@chromium.org>
Reviewed-by: default avatarDavid Hildenbrand <david@redhat.com>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220110231530.665970-4-willy@infradead.org
parent 0aef499f

mm/usercopy.c

+4 −6
Original line number Diff line number Diff line
@@ -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);