linux-hardening - [PATCH v2 1/2] slab: Clean up SLOB vs kmalloc() definition

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Date:   Thu, 17 Nov 2022 19:51:58 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Kees Cook <keescook@...omium.org>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: [PATCH v2 1/2] slab: Clean up SLOB vs kmalloc() definition

As already done for kmalloc_node(), clean up the #ifdef usage in the
definition of kmalloc() so that the SLOB-only version is an entirely
separate and much more readable function.

Cc: Vlastimil Babka <vbabka@...e.cz>
Cc: Christoph Lameter <cl@...ux.com>
Cc: Pekka Enberg <penberg@...nel.org>
Cc: David Rientjes <rientjes@...gle.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@....com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Roman Gushchin <roman.gushchin@...ux.dev>
Cc: Hyeonggon Yoo <42.hyeyoo@...il.com>
Cc: linux-mm@...ck.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 include/linux/slab.h | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/include/linux/slab.h b/include/linux/slab.h
index 1c670c16c737..9033937c758e 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -558,15 +558,15 @@ void *kmalloc_large_node(size_t size, gfp_t flags, int node) __assume_page_align
  *	Try really hard to succeed the allocation but fail
  *	eventually.
  */
+#ifndef CONFIG_SLOB
 static __always_inline __alloc_size(1) void *kmalloc(size_t size, gfp_t flags)
 {
 	if (__builtin_constant_p(size)) {
-#ifndef CONFIG_SLOB
 		unsigned int index;
-#endif
+
 		if (size > KMALLOC_MAX_CACHE_SIZE)
 			return kmalloc_large(size, flags);
-#ifndef CONFIG_SLOB
+
 		index = kmalloc_index(size);
 
 		if (!index)
@@ -575,10 +575,18 @@ static __always_inline __alloc_size(1) void *kmalloc(size_t size, gfp_t flags)
 		return kmalloc_trace(
 				kmalloc_caches[kmalloc_type(flags)][index],
 				flags, size);
-#endif
 	}
 	return __kmalloc(size, flags);
 }
+#else
+static __always_inline __alloc_size(1) void *kmalloc(size_t size, gfp_t flags)
+{
+	if (__builtin_constant_p(size) && size > KMALLOC_MAX_CACHE_SIZE)
+		return kmalloc_large(size, flags);
+
+	return __kmalloc(size, flags);
+}
+#endif
 
 #ifndef CONFIG_SLOB
 static __always_inline __alloc_size(1) void *kmalloc_node(size_t size, gfp_t flags, int node)
-- 
2.34.1