[PATCH 1/3] mm/usercopy: Check kmap addresses properly
From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Date: 2021-10-04 22:44:37
Subsystem:
kernel hardening (not covered by other areas), memory management, the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Kees Cook, Andrew Morton, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
If you are copying to an address in the kmap region, you may not copy across a page boundary, no matter what the size of the underlying allocation. You can't kmap() a slab page because slab pages always come from low memory. Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> --- arch/x86/include/asm/highmem.h | 1 + include/linux/highmem-internal.h | 10 ++++++++++ mm/usercopy.c | 15 +++++++++------ 3 files changed, 20 insertions(+), 6 deletions(-)
diff --git a/arch/x86/include/asm/highmem.h b/arch/x86/include/asm/highmem.h
index 032e020853aa..731ee7cc40a5 100644
--- a/arch/x86/include/asm/highmem.h
+++ b/arch/x86/include/asm/highmem.h@@ -26,6 +26,7 @@ #include <asm/tlbflush.h> #include <asm/paravirt.h> #include <asm/fixmap.h> +#include <asm/pgtable_areas.h> /* declarations for highmem.c */ extern unsigned long highstart_pfn, highend_pfn;
diff --git a/include/linux/highmem-internal.h b/include/linux/highmem-internal.h
index 4aa1031d3e4c..97d6dc836749 100644
--- a/include/linux/highmem-internal.h
+++ b/include/linux/highmem-internal.h@@ -143,6 +143,11 @@ static inline void totalhigh_pages_add(long count) atomic_long_add(count, &_totalhigh_pages); } +static inline bool is_kmap_addr(const void *x) +{ + unsigned long addr = (unsigned long)x; + return addr >= PKMAP_ADDR(0) && addr < PKMAP_ADDR(LAST_PKMAP); +} #else /* CONFIG_HIGHMEM */ static inline struct page *kmap_to_page(void *addr)
@@ -223,6 +228,11 @@ static inline void __kunmap_atomic(void *addr) static inline unsigned int nr_free_highpages(void) { return 0; } static inline unsigned long totalhigh_pages(void) { return 0UL; } +static inline bool is_kmap_addr(const void *x) +{ + return false; +} + #endif /* CONFIG_HIGHMEM */ /*
diff --git a/mm/usercopy.c b/mm/usercopy.c
index b3de3c4eefba..ac95b22fbbce 100644
--- a/mm/usercopy.c
+++ b/mm/usercopy.c@@ -228,12 +228,15 @@ static inline void check_heap_object(const void *ptr, unsigned long n, if (!virt_addr_valid(ptr)) return; - /* - * When CONFIG_HIGHMEM=y, kmap_to_page() will give either the - * highmem page or fallback to virt_to_page(). The following - * is effectively a highmem-aware virt_to_head_page(). - */ - page = compound_head(kmap_to_page((void *)ptr)); + if (is_kmap_addr(ptr)) { + unsigned long page_end = (unsigned long)ptr | (PAGE_SIZE - 1); + + if ((unsigned long)ptr + n - 1 > page_end) + usercopy_abort("kmap", NULL, to_user, 0, n); + return; + } + + page = virt_to_head_page(ptr); if (PageSlab(page)) { /* Check slab allocator for flags and size. */
--
2.32.0