From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
To: Kees Cook <keescook@chromium.org>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>,
linux-mm@kvack.org, linux-hardening@vger.kernel.org
Subject: [PATCH 1/4] mm/usercopy: Check kmap addresses properly
Date: Mon, 10 Jan 2022 23:15:27 +0000 [thread overview]
Message-ID: <20220110231530.665970-2-willy@infradead.org> (raw)
In-Reply-To: <20220110231530.665970-1-willy@infradead.org>
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>
Acked-by: Kees Cook <keescook@chromium.org>
---
arch/x86/include/asm/highmem.h | 1 +
include/linux/highmem-internal.h | 10 ++++++++++
mm/usercopy.c | 16 ++++++++++------
3 files changed, 21 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 0a0b2b09b1b8..01fb76d101b0 100644
--- a/include/linux/highmem-internal.h
+++ b/include/linux/highmem-internal.h
@@ -149,6 +149,11 @@ 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)
@@ -234,6 +239,11 @@ 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 d0d268135d96..2d13bc3bd83b 100644
--- a/mm/usercopy.c
+++ b/mm/usercopy.c
@@ -229,12 +229,16 @@ 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_slab().
- */
- folio = page_folio(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,
+ offset_in_page(ptr), n);
+ return;
+ }
+
+ folio = virt_to_folio(ptr);
if (folio_test_slab(folio)) {
/* Check slab allocator for flags and size. */
--
2.33.0
next prev parent reply other threads:[~2022-01-10 23:15 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-10 23:15 [PATCH 0/4] Assorted improvements to usercopy Matthew Wilcox (Oracle)
2022-01-10 23:15 ` Matthew Wilcox (Oracle) [this message]
2022-05-10 3:37 ` [PATCH 1/4] mm/usercopy: Check kmap addresses properly Andrew Morton
2022-05-10 22:01 ` Kees Cook
2022-01-10 23:15 ` [PATCH 2/4] mm/usercopy: Detect vmalloc overruns Matthew Wilcox (Oracle)
2022-01-10 23:15 ` [PATCH 3/4] mm/usercopy: Detect large folio overruns Matthew Wilcox (Oracle)
2022-01-31 14:28 ` David Hildenbrand
2022-01-10 23:15 ` [PATCH 4/4] usercopy: Remove HARDENED_USERCOPY_PAGESPAN Matthew Wilcox (Oracle)
2022-01-12 23:08 ` Kees Cook
2022-01-31 14:27 ` David Hildenbrand
2022-01-31 19:27 ` Matthew Wilcox
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