linux-hardening - [PATCH v4] mempool: Do not use ksize() for poisoning

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Message-Id: <20221028154823.you.615-kees@kernel.org>
Date:   Fri, 28 Oct 2022 08:53:01 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Kees Cook <keescook@...omium.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        David Rientjes <rientjes@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        linux-mm@...ck.org, Andrey Konovalov <andreyknvl@...il.com>,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: [PATCH v4] mempool: Do not use ksize() for poisoning

Nothing appears to be using ksize() within the kmalloc-backed mempools
except the mempool poisoning logic. Use the actual pool size instead
of the ksize() to avoid needing any special handling of the memory as
needed by KASAN, UBSAN_BOUNDS, nor FORTIFY_SOURCE.

Suggested-by: Vlastimil Babka <vbabka@...e.cz>
Link: https://lore.kernel.org/lkml/f4fc52c4-7c18-1d76-0c7a-4058ea2486b9@suse.cz/
Cc: David Rientjes <rientjes@...gle.com>
Cc: Marco Elver <elver@...gle.com>
Cc: Vincenzo Frascino <vincenzo.frascino@....com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-mm@...ck.org
Acked-by: Vlastimil Babka <vbabka@...e.cz>
Reviewed-by: Andrey Konovalov <andreyknvl@...il.com>
Signed-off-by: Kees Cook <keescook@...omium.org>
---
This replaces mempool-use-kmalloc_size_roundup-to-match-ksize-usage.patch
v4: add review/ack tags, explicitly call out subject change
v3: https://lore.kernel.org/lkml/20221025233421.you.825-kees@kernel.org/
v2: https://lore.kernel.org/lkml/20221018090323.never.897-kees@kernel.org/
v1: https://lore.kernel.org/lkml/20220923202822.2667581-14-keescook@chromium.org/
---
 mm/mempool.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/mempool.c b/mm/mempool.c
index 96488b13a1ef..54204065037d 100644
--- a/mm/mempool.c
+++ b/mm/mempool.c
@@ -58,7 +58,7 @@ static void check_element(mempool_t *pool, void *element)
 {
 	/* Mempools backed by slab allocator */
 	if (pool->free == mempool_free_slab || pool->free == mempool_kfree) {
-		__check_element(pool, element, ksize(element));
+		__check_element(pool, element, (size_t)pool->pool_data);
 	} else if (pool->free == mempool_free_pages) {
 		/* Mempools backed by page allocator */
 		int order = (int)(long)pool->pool_data;
@@ -81,7 +81,7 @@ static void poison_element(mempool_t *pool, void *element)
 {
 	/* Mempools backed by slab allocator */
 	if (pool->alloc == mempool_alloc_slab || pool->alloc == mempool_kmalloc) {
-		__poison_element(element, ksize(element));
+		__poison_element(element, (size_t)pool->pool_data);
 	} else if (pool->alloc == mempool_alloc_pages) {
 		/* Mempools backed by page allocator */
 		int order = (int)(long)pool->pool_data;
@@ -112,7 +112,7 @@ static __always_inline void kasan_poison_element(mempool_t *pool, void *element)
 static void kasan_unpoison_element(mempool_t *pool, void *element)
 {
 	if (pool->alloc == mempool_alloc_slab || pool->alloc == mempool_kmalloc)
-		kasan_unpoison_range(element, __ksize(element));
+		kasan_unpoison_range(element, (size_t)pool->pool_data);
 	else if (pool->alloc == mempool_alloc_pages)
 		kasan_unpoison_pages(element, (unsigned long)pool->pool_data,
 				     false);
-- 
2.34.1