There isn't enough information to make this a useful check any more;
the useful parts of it were moved in earlier patches, so remove this
set of checks now.
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
mm/usercopy.c | 61 ------------------------------------------------
security/Kconfig | 13 +----------
2 files changed, 1 insertion(+), 73 deletions(-)
diff --git a/mm/usercopy.c b/mm/usercopy.c
index e1cb98087a05..94831945d9e7 100644
--- a/mm/usercopy.c
+++ b/mm/usercopy.c
@@ -158,64 +158,6 @@ static inline void check_bogus_address(const unsigned long ptr, unsigned long n,
usercopy_abort("null address", NULL, to_user, ptr, n);
}
-/* Checks for allocs that are marked in some way as spanning multiple pages. */
-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;
- bool is_reserved, is_cma;
-
- /*
- * Sometimes the kernel data regions are not marked Reserved (see
- * check below). And sometimes [_sdata,_edata) does not cover
- * rodata and/or bss, so check each range explicitly.
- */
-
- /* Allow reads of kernel rodata region (if not marked as Reserved). */
- if (ptr >= (const void *)__start_rodata &&
- end <= (const void *)__end_rodata) {
- if (!to_user)
- 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;
-
- /* Allow kernel bss region (if not marked as Reserved). */
- if (ptr >= (const void *)__bss_start &&
- end <= (const void *)__bss_stop)
- 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;
-
- /*
- * Reject if range is entirely either Reserved (i.e. special or
- * device memory), or CMA. Otherwise, reject since the object spans
- * several independently allocated pages.
- */
- is_reserved = PageReserved(page);
- is_cma = is_migrate_cma_page(page);
- if (!is_reserved && !is_cma)
- 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))
- usercopy_abort("spans Reserved and non-Reserved pages",
- NULL, to_user, 0, n);
- if (is_cma && !is_migrate_cma_page(page))
- usercopy_abort("spans CMA and non-CMA pages", NULL,
- to_user, 0, n);
- }
-#endif
-}
-
static inline void check_heap_object(const void *ptr, unsigned long n,
bool to_user)
{
@@ -257,9 +199,6 @@ static inline void check_heap_object(const void *ptr, unsigned long n,
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);
}
}
diff --git a/security/Kconfig b/security/Kconfig
index 0b847f435beb..5b289b329a51 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -160,20 +160,9 @@ config HARDENED_USERCOPY
copy_from_user() functions) by rejecting memory ranges that
are larger than the specified heap object, span multiple
separately allocated pages, are not on the process stack,
- or are part of the kernel text. This kills entire classes
+ or are part of the kernel text. This prevents entire classes
of heap overflow exploits and similar kernel memory exposures.
-config HARDENED_USERCOPY_PAGESPAN
- bool "Refuse to copy allocations that span multiple pages"
- depends on HARDENED_USERCOPY
- depends on EXPERT
- help
- When a multi-page allocation is done without __GFP_COMP,
- hardened usercopy will reject attempts to copy it. There are,
- however, several cases of this in the kernel that have not all
- been removed. This config is intended to be used only while
- trying to find such users.
-
config FORTIFY_SOURCE
bool "Harden common str/mem functions against buffer overflows"
depends on ARCH_HAS_FORTIFY_SOURCE
--
2.33.0
