[PATCH v2 3/3] mm/usercopy: Detect compound page overruns
From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Date: 2021-10-06 12:46:46
Subsystem:
kernel hardening (not covered by other areas), memory management, the rest · Maintainers:
Kees Cook, Andrew Morton, Linus Torvalds
Move the compound page overrun detection out of CONFIG_HARDENED_USERCOPY_PAGESPAN so it's enabled for more people. Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Acked-by: Kees Cook <redacted> --- mm/usercopy.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/mm/usercopy.c b/mm/usercopy.c
index 63476e1506e0..b825c4344917 100644
--- a/mm/usercopy.c
+++ b/mm/usercopy.c@@ -194,11 +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
@@ -258,6 +253,11 @@ static inline void check_heap_object(const void *ptr, unsigned long n, if (PageSlab(page)) { /* Check slab allocator for flags and size. */ __check_heap_object(ptr, n, page, to_user); + } else if (PageHead(page)) { + /* A compound allocation */ + unsigned long offset = ptr - page_address(page); + if (offset + n > page_size(page)) + usercopy_abort("page alloc", NULL, to_user, offset, n); } else { /* Verify object does not incorrectly span multiple pages. */ check_page_span(ptr, n, page, to_user);
--
2.32.0