linux-hardening - [PATCH 2/3] usercopy: Cast pointer to an integer once

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Date:   Sun, 12 Jun 2022 22:32:26 +0100
From:   "Matthew Wilcox (Oracle)" <willy@...radead.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        linux-mm@...ck.org, Uladzislau Rezki <urezki@...il.com>,
        Zorro Lang <zlang@...hat.com>, linux-xfs@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: [PATCH 2/3] usercopy: Cast pointer to an integer once

Get rid of a lot of annoying casts by setting 'addr' once at the top
of the function.

Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
---
 mm/usercopy.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/mm/usercopy.c b/mm/usercopy.c
index fdd1bed3b90a..31deee7dd2f5 100644
--- a/mm/usercopy.c
+++ b/mm/usercopy.c
@@ -161,19 +161,20 @@ static inline void check_bogus_address(const unsigned long ptr, unsigned long n,
 static inline void check_heap_object(const void *ptr, unsigned long n,
 				     bool to_user)
 {
+	uintptr_t addr = (uintptr_t)ptr;
 	struct folio *folio;
 
 	if (is_kmap_addr(ptr)) {
-		unsigned long page_end = (unsigned long)ptr | (PAGE_SIZE - 1);
+		unsigned long page_end = addr | (PAGE_SIZE - 1);
 
-		if ((unsigned long)ptr + n - 1 > page_end)
+		if (addr + n - 1 > page_end)
 			usercopy_abort("kmap", NULL, to_user,
 					offset_in_page(ptr), n);
 		return;
 	}
 
 	if (is_vmalloc_addr(ptr)) {
-		struct vmap_area *area = find_vmap_area((unsigned long)ptr);
+		struct vmap_area *area = find_vmap_area(addr);
 		unsigned long offset;
 
 		if (!area) {
@@ -183,8 +184,8 @@ static inline void check_heap_object(const void *ptr, unsigned long n,
 
 		/* XXX: We should also abort for free vmap_areas */
 
-		offset = (unsigned long)ptr - area->va_start;
-		if ((unsigned long)ptr + n > area->va_end)
+		offset = addr - area->va_start;
+		if (addr + n > area->va_end)
 			usercopy_abort("vmalloc", NULL, to_user, offset, n);
 		return;
 	}
-- 
2.35.1