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mm/usercopy: Detect large folio overruns

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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@infradead.org>
Acked-by: Kees Cook <keescook@chromium.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220110231530.665970-4-willy@infradead.org
This commit is contained in:
Matthew Wilcox (Oracle) 2022-01-10 23:15:29 +00:00 committed by Kees Cook
parent 0aef499f31
commit ab502103ae
1 changed files with 4 additions and 6 deletions
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10
mm/usercopy.c
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@ -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);