kasan: ensure poisoning size alignment

A previous changes d99f6a10c161 ("kasan: don't round_up too much")
attempted to simplify the code by adding a round_up(size) call into
kasan_poison().  While this allows to have less round_up() calls around
the code, this results in round_up() being called multiple times.

This patch removes round_up() of size from kasan_poison() and ensures that
all callers round_up() the size explicitly.  This patch also adds
WARN_ON() alignment checks for address and size to kasan_poison() and
kasan_unpoison().

Link: https://lkml.kernel.org/r/3ffe8d4a246ae67a8b5e91f65bf98cd7cba9d7b9.1612546384.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Branislav Rankov <Branislav.Rankov@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 22 insertions, 15 deletions

diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c
index 1ed7817e4ee6..63f43443f5d7 100644
--- a/mm/kasan/shadow.c
+++ b/mm/kasan/shadow.c
@@ -69,7 +69,7 @@ void *memcpy(void *dest, const void *src, size_t len)
 	return __memcpy(dest, src, len);
 }
 
-void kasan_poison(const void *address, size_t size, u8 value)
+void kasan_poison(const void *addr, size_t size, u8 value)
 {
 	void *shadow_start, *shadow_end;
 
@@ -78,55 +78,62 @@ void kasan_poison(const void *address, size_t size, u8 value)
 	 * some of the callers (e.g. kasan_poison_object_data) pass tagged
 	 * addresses to this function.
 	 */
-	address = kasan_reset_tag(address);
+	addr = kasan_reset_tag(addr);
 
 	/* Skip KFENCE memory if called explicitly outside of sl*b. */
-	if (is_kfence_address(address))
+	if (is_kfence_address(addr))
 		return;
 
-	size = round_up(size, KASAN_GRANULE_SIZE);
-	shadow_start = kasan_mem_to_shadow(address);
-	shadow_end = kasan_mem_to_shadow(address + size);
+	if (WARN_ON((unsigned long)addr & KASAN_GRANULE_MASK))
+		return;
+	if (WARN_ON(size & KASAN_GRANULE_MASK))
+		return;
+
+	shadow_start = kasan_mem_to_shadow(addr);
+	shadow_end = kasan_mem_to_shadow(addr + size);
 
 	__memset(shadow_start, value, shadow_end - shadow_start);
 }
 EXPORT_SYMBOL(kasan_poison);
 
 #ifdef CONFIG_KASAN_GENERIC
-void kasan_poison_last_granule(const void *address, size_t size)
+void kasan_poison_last_granule(const void *addr, size_t size)
 {
 	if (size & KASAN_GRANULE_MASK) {
-		u8 *shadow = (u8 *)kasan_mem_to_shadow(address + size);
+		u8 *shadow = (u8 *)kasan_mem_to_shadow(addr + size);
 		*shadow = size & KASAN_GRANULE_MASK;
 	}
 }
 #endif
 
-void kasan_unpoison(const void *address, size_t size)
+void kasan_unpoison(const void *addr, size_t size)
 {
-	u8 tag = get_tag(address);
+	u8 tag = get_tag(addr);
 
 	/*
 	 * Perform shadow offset calculation based on untagged address, as
 	 * some of the callers (e.g. kasan_unpoison_object_data) pass tagged
 	 * addresses to this function.
 	 */
-	address = kasan_reset_tag(address);
+	addr = kasan_reset_tag(addr);
 
 	/*
 	 * Skip KFENCE memory if called explicitly outside of sl*b. Also note
 	 * that calls to ksize(), where size is not a multiple of machine-word
 	 * size, would otherwise poison the invalid portion of the word.
 	 */
-	if (is_kfence_address(address))
+	if (is_kfence_address(addr))
+		return;
+
+	if (WARN_ON((unsigned long)addr & KASAN_GRANULE_MASK))
 		return;
 
-	/* Unpoison round_up(size, KASAN_GRANULE_SIZE) bytes. */
-	kasan_poison(address, size, tag);
+	/* Unpoison all granules that cover the object. */
+	kasan_poison(addr, round_up(size, KASAN_GRANULE_SIZE), tag);
 
 	/* Partially poison the last granule for the generic mode. */
 	if (IS_ENABLED(CONFIG_KASAN_GENERIC))
-		kasan_poison_last_granule(address, size);
+		kasan_poison_last_granule(addr, size);
 }
 
 #ifdef CONFIG_MEMORY_HOTPLUG